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eHam Forums => Amplifiers => Topic started by: WU2M on January 21, 2013, 04:52:32 PM



Title: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 21, 2013, 04:52:32 PM
Hello All,

I just purchased a Ten Tec Titan 425 amp used. I hooked it up and ran it to test everything. All seemed to be working well but as it sat running it blew one of the 20 amp fuses. I replaced the fuse and tried to power it up again and it would not power up. I pulled the tubes out and tried again and still nothing so I pulled the cover off the power supply and found that the 1.5 amp fuse had blown. I replaced the fuse and as soon as I turned it on, it blew the 1.5 amp fuse again.
 The previous owner told me when I purchased it that he had replaced the filter caps in the power supply.
Any suggestions? I would like to get this thing running as my backup amp.

Thanks,

Rocco WU2M


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KC4MOP on January 21, 2013, 05:23:57 PM
Sounds like the amp didn't make the trip shipping too well.
Were the tubes removed during shipping? Shouldn't have been a problem. But something not happy now!
My personal opinion about the 425 is that I would never own another one. Extremely difficult to get into and service. Mine had a defective band switch and Ten Tec charged me $750.00 to repair. I dealt with that repair and got rid of it immediately and bought an Ameritron AL1500.
Fred


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KA5N on January 21, 2013, 05:30:05 PM
Fuses blow because there is too much current flowing through them.  This is usually because
of a short somewhere.  If you have a DVM or multimeter, with the power off and the amp
unplugged check for shorts.  Most often shorts will be in the power supply section.  
Did you see the amp operating before you bought it?  Just because the previous owner says
that he replaced the filter caps doesn't mean that he did, or if he did replace them that the
new ones were good, or that he put them in with the correct polarity connections. ETC.
If you don't know how to troubleshoot an amplifier then get local help from some knowledgeble
ham. Tube type Amplifiers have lethal voltages present when powered up which can produce
deadly shocks.  BE CAREFUL!!
Allen   KA5N


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 21, 2013, 05:36:06 PM
The tubes were not removed for shipping and I did not see it run. The shipping was excellent with everything double boxed, transformer removed and bolted to a board. Everything was wrapped in bubble wrap and then surrounded with peanuts.
 The amp I had the amp running for about 4 hours and I made several contacts with it. It was just sitting there running in the stand by position when the fuse blew. I was thinking abut sending it to Tan-Tec but $750.00 to change a band switch sounds a bit high to me. I hate to eat the thing and pull the tubes for spares for my Alpha89 thats for sure.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on January 21, 2013, 06:34:40 PM
On the other hand, one single report of a large repair bill does not a trend make. 

This could be something as simple as a shorted rectifier or a tube that shorted. 



Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on January 21, 2013, 06:39:08 PM
Do you have a manual for the amp?  Do you have the schematic for the amp?  I looked on line for the schematic and from what I can tell there is a low current fuse in the power supply.  The fuse SHOULD BE A 4 AMP SLOW BLOW FUSE.  If you have a 1.5 amp fast acting fuse that could be why it is blowing.  I did not have a complete schematic but if there is only one low current glass fuse in the power supply other thasn the 20A mains then it should be a 4 Amp slow blow not a 1.5 fast acting.  SO that could be your problem.  Check the schematic and see because that is what I see in there. Lou


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 21, 2013, 06:45:29 PM
Rocco:

I have had the unpleasant experience of servicing the 425 on numerous occasions.  I really do not like working on the power supply as it is very tight, and you have to unsolder wire harnesses to pull the printed circuit boards out.

If I recall correctly, the 1.5A fuse is for the 28V supply.   There should be a smaller set of rectifiers and an Electrolytic associated with this part of the supply. Check those for a short. The diodes in question should be found on the AC board which also contains two relays.

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 21, 2013, 06:52:13 PM
I just pulled the schematic I have from the basement.  You did not specify which 1.5A Fuse. It appears as though there is another 1.5A associated with K7. This is your softstart relay.  Check there too!

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 21, 2013, 07:02:12 PM
First of all, I want to thank everyone for their help and replies. The fuse I am talking about is F3 which the schematic shows to be a 1.5A slow blow. I will check around for a short. To be honest, this thing scares me a bit due to the high voltage.
 Another question that I have is should I pull the tubes out and try to power up the amp after I find the problem with the power supply? I'm not sure how I would test them other than to put them in my primary amp and fire it up.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 21, 2013, 07:08:20 PM
Hi Rocco:

In this case, I would not worry about pulling the tube. Seperate the Power Supply from the RF Deck. If the amplfier has been in operation recently, make sure the crowbar falls down on the HV connector, and I would wait until tomorrow to start looking.

The failure I have seen here most often is a open R1 which does not sound like your issue, but take a look at it anyway to see if it looks as though its been "cooking".

Next I would check the values of R3 - R5, and C6 as this sets up the RC time constant for RL K7A. If something has gone amiss here, it may explain why you are seeing F3 Blow.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KC4MOP on January 22, 2013, 04:42:32 AM
Please remember the High voltage rules working in this amplifier!!.
I was not trying to scare the OP, but Ten Tec did a good repair. The bandswitch is buried deep deep inside the amp. They wanted a very compact design to sit on your desk.
The power supply filters are easy to replace. I got mine from Mouser and they were exact replacements.
I hope your fuse is just needing to go to slow blow and you might be ok.
Let us know how you get this resolved.
Fred


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on January 22, 2013, 05:44:00 AM
What fuse did I see labled 4A slow blow?  I can't seem to find a schematic in full.  The PDF on the Ten Tec website seems to be cut off.  But from what I am hearing my approach to the problem would be to pull the tubes out.  Doing so eliminates them as probable cause.  If all is OK with them out then put them back in.  if something goes wrong then it is a safe bet one or both tubes have an issue.  When doing any type of repair work it is good to do one thing at a time and see if the one thing solves the problem this way one learns what the problem was instead of guessing what was wrong if you shot gun it.  I have 2 of these amps stored away but when I used to use them I really liked them very much.  I did not have to work on them however, but I did look inside the power supply and it sure is busy in there and could imagine it is hard to service.  I do remember that.  I would think that if the problem was with the step start the fuse would blow right away and not 10 minutes down the road.  SInce I can't seem to get the schematic off the net I would think that the problem is with whatever circuit that fuse protects.  I don;t have my manual handy to look at.  it is stored away someplace.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 22, 2013, 09:45:31 AM
I'm not sure where the 4A fuse would be located. I looked at the schematic and I don't see one in my amp. F3 is the 1.5A fuse that I have the issue with at the moment. When the problem first happened, it blew that and one of the 20A fuses as well. I am going to try to see what I can come up with this weekend otherwise I'm afraid I'm going to have the box the whole thing up and send it to Ten-Tec unless someone has a power supply for a Titan that they want to sell which is unlikely.
 While the amp was running, everything seemed normal with it. I checked it over and made sure it was clean inside bothe the power supply and the RF deck. I did notice that the HV seemed to be on the lower end of what the manual said it should be but it was still withing
it's operating perameters so I didn't think anything of it. It loaded up normally and the power output was as it should be. It was just sitting there in the stand by mode when I heard the fuse pop and the power went out.
 I checked the outlet and it is at 243VAC so that should not be an issue. I will update everyone on what I find. Again, I want to thank everyone for the help and advice I am getting, it is greaty appreciated!

Rocco
WU2M


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 22, 2013, 10:11:39 AM
I'm not sure where the 4A fuse would be located. I looked at the schematic and I don't see one in my amp. F3 is the 1.5A fuse that I have the issue with at the moment. When the problem first happened, it blew that and one of the 20A fuses as well.
 
I did notice that the HV seemed to be on the lower end of what the manual said it should be but it was still withing it's operating perameters so I didn't think anything of it. WU2M

Rocco - What you describe could certianly happen if the problem were in the Soft Start Circuit as I described in an earlier post. Have you been able to open the power supply today and take a look at the components I called out?

Rich, AJ3G


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on January 22, 2013, 12:45:22 PM
...It was just sitting there in the stand by mode when I heard the fuse pop and the power went out.
 

All the more reason to suspect a powerline transient that popped a rectifier.

Rather common problem if the stuff that passes over my testbench is any indication. 

I LIKE it when I find such, for it is easy to find, "walk" every rectifier you see using the ohmmeter on diode scale function, the failure mode of the rectifier is nearly always a dead short. 

And, the rectifier will fail as a short, faster than a fuse can react, thus protecting other more epensive components that are wired in after that rectifier. 


Good Troubleshooting,


73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W8JX on January 22, 2013, 02:19:58 PM
My thoughts here are that a bleeder opened up and a CAP shorted out. Diodes are generally pretty reliable here.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 22, 2013, 02:44:38 PM
Rocco:

I just took another look at the schematic, can you tell us if F2 was the 20A fuse which blew, in conjuntion with F3?  It it is, then the problem almost has to be in the soft start circuit.

73

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 22, 2013, 03:03:21 PM
Rich,
 In looking at the schematic F2 is the 20 amp fuse that blew the first time with F3. I am going to take a look at R2 (20 ohm 25 watt) as upon close inspection, it looks like part of the side of it has blown away and I can see the wire on the inside. I don't think this is normal but I don't have a lot of experience here. There is nothing inside to support that though.

73
Rocco


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 22, 2013, 03:09:13 PM
Hello Rocco:

I show the 20 Ohm resistor as R1, and if it looks charred or burned, then the odds are you have a softstart issue which needs to be fixed.  If you look to the right of R1 on the top of the schematic you will note a box makred K7A.  I would check to make sure you have voltage at the junnction of D2/D3/C3. If you have voltage there then check it again at the top of C6, and let me know what you find.

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 22, 2013, 04:00:00 PM

Rocco:

I made a pretty hair brain statement in my last post. I forgot, you cannot check the voltage because you keep blowing fuses! :P

You are going to have to check each component by pulling it from the board and testing. If you have a bench supply, you may want to test K7A to make sure it is closing when the appropriate voltage is applied.

Here is what I suspect are the problems:

1. Failure in the 28V Supply associated with D1-D4, and C3.

2. Failed or out of tolerance component in the RC Time Delay circuit (C6/R3/R4/R5).

3. K7A Failed or Corrosion on the contacts.

What is probably happening here is, K7A is not being switched in on time, or not at all, causing R1 to get very HOT as you can see from your previous posted observation.

Since you will likely have to pull the board at this point; make sure you look at the bottom very carefully. I hate to say it, but those boards are not very well constructed, and I have seen on several occasions were the foil on the bottom of the board burns up before the fuse blows.

I once joked with a Ten Tec technician on why they even bothered to utilize fuses as the foil on their PCB's seems to do just as good as a job!


73

Rich, AJ3G




Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on January 22, 2013, 06:02:02 PM
My thoughts here are that a bleeder opened up and a CAP shorted out. Diodes are generally pretty reliable here.

Not the ones in the soft start circuit. 

Pretty much box standard rectification here, not talking about high voltage supply.


73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KC4MOP on January 22, 2013, 06:08:39 PM
...It was just sitting there in the stand by mode when I heard the fuse pop and the power went out.
 

All the more reason to suspect a powerline transient that popped a rectifier.

Rather common problem if the stuff that passes over my testbench is any indication. 

I LIKE it when I find such, for it is easy to find, "walk" every rectifier you see using the ohmmeter on diode scale function, the failure mode of the rectifier is nearly always a dead short. 

And, the rectifier will fail as a short, faster than a fuse can react, thus protecting other more epensive components that are wired in after that rectifier. 


Good Troubleshooting,


73
I would believe a power line transient in a third world country or during a very hot Summer and power companies are rolling blackouts. Conditions for the USA power companies has been stable the last couple of years

It will be interesting to read what W2UM decides to do next. I guess he opened the rig up. I read another post here and now remember about the crow bar. If he is trying to power up with the covers off then the crowbar will do its thing.......short out the PS.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 22, 2013, 07:59:31 PM
I put the covers back on before I fire it up again. I will pull the board out tomorrow night and try to troubleshoot the board. I have very limited test equipment and only basic knowledge so it may take me awhile.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on January 23, 2013, 10:54:39 AM

I would believe a power line transient in a third world country or during a very hot Summer and power companies are rolling blackouts. Conditions for the USA power companies has been stable the last couple of years.

My experiences on the test bench daily do not bear that out.  Appliances of all types pass through here, the shorted rectifier in either a bridge config as in analog supply, and also at the front of Switching Power supplies is really a common thing.  It doesn't take much to exceed the Reverse Voltage spec and turn the junction into a busbar. 

Transients can be caused by natural events, such as lightning strike or even just static buildup on a power line.  Then there can be the situation where something else on the same AC may be turning off and has a big coil across the line that, when its mag field drops, generates a voltage spike much higher than the line voltage. 

Quote
It will be interesting to read what W2UM decides to do next. I guess he opened the rig up. I read another post here and now remember about the crow bar. If he is trying to power up with the covers off then the crowbar will do its thing.......short out the PS.

Interesting indeed. 

From what I've been able to gather on this thread, it is looking more and more like the problem lies in the Softstart circuit, which is powered by -- bridge rectifier. 

73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 25, 2013, 03:26:17 AM
Between work and home, I have not had a chance to get back to the amp. My plan is to pull the board out and test the components in the soft start one at a time and hopefully I can find the problem. I am looking forward to starting that tonight. My shack is small so I have to set up another table tonight and go after it. If I get nowhere, I am going to look into sending it to Ten Tec for repair unless someone here knows of a better place.

Rocco
WU2M


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 25, 2013, 04:24:07 AM
Hello Rocco:

Sounds like you have a good plan in place. One recommendation, I would have something available which you can mark the wires with. You are going to have to unsolder some fo the hook up wires to the board to get it out of the chassis. You want to make sure they all go back where they are supposed to.

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on January 25, 2013, 07:07:10 AM
Hello Rocco:

Sounds like you have a good plan in place. One recommendation, I would have something available which you can mark the wires with. You are going to have to unsolder some fo the hook up wires to the board to get it out of the chassis. You want to make sure they all go back where they are supposed to.

Rich

Very good suggestion. 

These days, use of a digital camera or one in yer cellphone can make short work of such documentation, snap a good and well lit, clear shot of each stage of disassembly and use the pics as the guide to reassembly. 

73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 25, 2013, 11:07:59 AM
Update:
 I marked all the wires and pulled the board out. I have not pulled out all the componenets yet. I thought I would order the three electrolytic capacitors and replace them as I know they get old. There are only three on the rectifier board anyway. However, I ran quickly through the diodes without pulling them and I think they all test good. I can't remember, do I need to pull these to test them correctly?

Thanks All
Rocco
WU2M


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 25, 2013, 12:49:42 PM
Hello Rocco:

Here is what I would do.  Lift the cathode side (the side which has the band on it) of each of the diodes (D1-D4).  Place the negative lead on the cathode and the positive lead on the anode. You should see around .700 V (or something close) displayed on your DMM if you have a diode test capability. If you do not have a diode test capability, then switch you meter to Ohms and with the Black Lead on the Cathode, and Red Lead on the Anode, you should see around 2 MEGA OHMS.

Now do the exact opposite on each of the diodes. Take the Red Lead and place it on the Cathode (The Banded Side), and the Black Lead on the anode. Each diode should read almost like an open circuit.

Testing them in the circuit without lifting one of the leads may give you the false impression you have a good diode. You need to break the connections at each of the junctions in order to test all the diodes in the full wave bridge rectifier.

73

Rich, AJ3G


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on January 25, 2013, 04:17:26 PM
Update:
 I marked all the wires and pulled the board out. I have not pulled out all the componenets yet. I thought I would order the three electrolytic capacitors and replace them as I know they get old. There are only three on the rectifier board anyway. However, I ran quickly through the diodes without pulling them and I think they all test good. I can't remember, do I need to pull these to test them correctly?

Thanks All
Rocco
WU2M

Power Rectifiers in a bridge configuration don't have to be disconnected to quickly check them.  Set your DMM to the Diodes scale and check each junction in both directions.  A good junction will readout the voltage drop in one direction and not conduct at all in the other.  A bad rectifier's failure mode is going to be a short, any one that reads near 0 volts in both directions is bad.  

If the rectifiers check good, the next thing I would suspect is any transistor immediately following them, such as might be found in a regulator circuit.  This because of the way you reported the failure to have happened. 

73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 25, 2013, 04:45:11 PM

There is NO Regulator after the rectifier, just a filter Capacitor and then on to the the RC Time Constant circuit.  



Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 25, 2013, 06:05:49 PM
I will lift the diodes and check them as suggested. Testing them in the circuit shows them all to be good. The Electrolytics seem to be good as well. I will be able to spend more time troubleshooting tomorrow, hopefully, I can find the issue.

Rocco
WU2M


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 25, 2013, 06:34:59 PM
If you are satisfied the Bridge is good, then start checking R3-R5 (470 Ohm's), and C6 (1000 uF @ 25V).  If all of this looks good in the time delay circuitry then there is only two parts that can be defective.

1. K7A is malfunctioning (Can Be Tested with a Bench Supply)

2. There is an issue with the low voltage secondary winding of the transformer.

To check the low voltage winding you are going to have to check the resistance of the secodary by placiong you DMM porbes between Pins 4 and 3 of the transformer. For your sake, I really hope the issue is either the RC Time Constant Network or the Relay, as a bad secondary on this transformer could be a very expensive fix, should you decide to replace it.

Of course we are not there yet, and there are other alternatives, but it would require adding another low voltage transformer into the power supply. Lets hope this is not the case!

On a other note, did you check the bottom of the board to make sure there is no burned or scortched foil?


Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 26, 2013, 07:37:25 AM
I checked the traces on the board and everything looks as it should. I am starting to wonder if something in the RF deck could be shorted and causing the 1.5 amp fuse to blow. I did try to power it up without the tubes to be sure it wasn't a shorted tube. When i did that and each time i tried, i put the covers on to be sure all the interlocks were not active.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 26, 2013, 07:48:44 AM
I checked the traces on the board and everything looks as it should. I am starting to wonder if something in the RF deck could be shorted and causing the 1.5 amp fuse to blow. I did try to power it up without the tubes to be sure it wasn't a shorted tube. When i did that and each time i tried, i put the covers on to be sure all the interlocks were not active.

Hi Rocco: 

I am not sure what to make of the above statement. Are you saying that it works without the tube installed, or removing the tube did not solve the problem?

I have never seen this mode of failure associated with a shorted tube, thus I would be a bit suprised if this turned out to be the case.

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 26, 2013, 08:48:41 AM
Rich,
 Removing the tubes did not solve the problem. I have just finished checking D-1 - D-4 with them out of line and they all test fine.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W8JX on January 26, 2013, 10:02:15 AM
Did you test bleeder resistors?


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 26, 2013, 11:39:00 AM
Rocco:

You need to start looking at the RC Time Constant circuit as suggested in my previous post.  Also, have you ordered a replacement for R1 (20 Ohm @ 25 Watt)?  Since you have the board pulled, and you have noted it has been getting hot, which is indicative of the Soft Start Failure, you should go ahead and replace it.

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 26, 2013, 11:58:13 AM
I have ordered a replacement for R1. It tests ok but looks like it is getting real hot. I have tested about everything on the rectifier board and so far, all look good.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 26, 2013, 12:12:51 PM
If you have tested R3 - R5 and C6, then the next step is to test K7A itself.  The way I would do this is to first make sure you have reasonable coil impedance with your Multimeter, and then apply DC Voltage to the coil and see if you can here K7A pickup, or click.  If it does make the clicking sound, then I would look at the contact side of the relay, and make sure you have good continuity.

I am not sure what you have in the way of bench supplies, but you MAY be able to close the relay with just 12 - 13.8V, but it would be better if you could provide 24V or close to it by wiring two supplies in series or have a bench supply which provides the required voltage.  I know you have done a lot of work so far, but I have seen two of these relays go bad in the 20+ Titans I have repaired over the years.

The one thing I will say about the 425, the RF Deck is pretty "bullet proof", but the Power Supply leaves a lot to be desired. This is exellent expierence to prepare you for the future!

Rich, AJ3G


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 27, 2013, 01:21:29 PM
Unfortunately, I don't have a way to test the relay so I guess it's off to Ten Tec with the power supply. May be best as I could have missed something because my troubleshooting skills are not that good!
 I did inquire about a transformer. It looks like 650.00 for a new one or 350.00 to rewind the old one. Ouch! Let's hope thats not the problem!


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on January 27, 2013, 02:18:11 PM
Before I sent that back in to TenTec, you may want to measure the Low Voltage secondary with a ohm meter, and see if you get a reasonable result (i.e. Not OPEN, or a Dead Short).  The reason I say this is, the whole AC board is $109.99, and if you can determine it's not the transformer, it may be worth it to buy the whole CCA. 

The reason I say this is, by the time you ship the supply back to TenTec, and have it looked at, you are more than likley going to exceed the cost of the AC Board!

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KC4MOP on January 28, 2013, 04:48:17 AM
Before I sent that back in to TenTec, you may want to measure the Low Voltage secondary with a ohm meter, and see if you get a reasonable result (i.e. Not OPEN, or a Dead Short).  The reason I say this is, the whole AC board is $109.99, and if you can determine it's not the transformer, it may be worth it to buy the whole CCA. 

The reason I say this is, by the time you ship the supply back to TenTec, and have it looked at, you are more than likley going to exceed the cost of the AC Board!

Rich
hmmmmm there was a post earlier about my comments about expensive repairs for a Ten Tec product.
I was lucky in my repair need, in that I knew my problem was in the band-switch and I did not want to tackle that design night mare in my Titan 425.
It's been about three years since my Ten Tec experience.
How about this??? BE CAREFUL WITH the extreme High Voltages!!! Have you disconnected the RED lead from the Amplifier chassis? Turn on the amplifier, cables connected, except for the RED LEAD?? Does the fuse still blow?
Have you located which circuit is affected by the blowing fuse? Without a schematic and electronic knowledge, you are in trouble. Is a download available??
I had a similar problem with blowing fuses and it was something on the main P.S....might have been the soft start. Earlier posts here reminded me about 28 volts somewhere.
Anyway to deal with the original owner?? That rig is very heavy to ship around.
Fred


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 29, 2013, 06:57:11 PM
I have not tried to fire it up without the HV line connected. I will have to wait until my parts get here to try that. I am hoping to have the parts I ordered by the weekend and then I will put it back together and see what happens. I posted an add looking for a power supply but that is just a long shot. I figured if someone had a dead RF deck it may be possible to get my hands on one. If not, I guess I'm going to box it up and send it off to Ten Tec.
 Another option was to pull the tubes and sell it off for salvage but I hate to take that hard a hit on it.

Rocco


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on January 31, 2013, 08:00:06 PM
Update:
 Replaced a few parts in the PS that were suspect. Fired up the amp and it ran for about 5 minutes and did the same thing again. I have decided that I am going to send it out and have it repaired and if it's not worth fixing, turn it in to scrap!
 Thanks to all who have responded!

Rocco


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 01, 2013, 12:50:56 AM
Rocco, check your PM box for a message.  Lou


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KC4MOP on February 02, 2013, 04:01:02 AM
Very Sorry for your situation. I would not want to start a finger pointing game to the seller, but I would guess he may have been aware of a problem and that is why he sold it, hoping it would fail on your shift after a few uses, and he would be in the clear.
I know you are pretty frustrated now, but you mention you have another amp using the same PA tubes. Did you plug them into the Ten Tec? The thread is long and I thought I looked at all of the pages.
Maybe in your PM someone is willing to take your project on to try to repair.
My comment on page one stands as I posted it. The band switch is buried deep inside the amp. The amp is a compact design to fit nicely on your desktop. So there's a price to pay for that compactness.
I knew my problem, but unwilling to take that horribly designed amp apart. I let Ten Tec do it at $75 per hour labor. The switch was under $100.00. The rest was very intense labor. It returned working perfectly and made 2500W OUT. Sold it, and bought something BIG so I can work on it. The AL 1500 Ameritron.
Fred


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 02, 2013, 04:14:09 AM
Fred, Lou W1QJ here.  I sent Rocco a private mesaage to contact me.  He called me on the phone last night.  We talked about his amp.  He never blamed the last owner at all.  He is a real sport about this problem.  He had the amp and power supply packed and ready to go to TT.  I am much closer to him then TN.  I am in CT.  He is sending the amp to me and I am going to check it out.  Providing the power transformer is good I will have the PS fixed.  I'll rebuild the step start if I have to.  I have 2 of these amps myself.  Our Lunar Link business uses a similar step start system.  I am familair with the circuit and know right where to look for the problem.  I will let eveyone know here what I found.  But my gut tells me I might just redesign the step start and just move forward.  We'll see.  Checking the circuit I see quite a few resistors that drop voltage and over time may be problematic.  I tend to take a more straight forward approach.  Stay tuned for more info as I have it. Lou


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KC4MOP on February 02, 2013, 11:18:36 AM
Fred, Lou W1QJ here.  I sent Rocco a private mesaage to contact me.  He called me on the phone last night.  We talked about his amp.  He never blamed the last owner at all.  He is a real sport about this problem.  He had the amp and power supply packed and ready to go to TT.  I am much closer to him then TN.  I am in CT.  He is sending the amp to me and I am going to check it out.  Providing the power transformer is good I will have the PS fixed.  I'll rebuild the step start if I have to.  I have 2 of these amps myself.  Our Lunar Link business uses a similar step start system.  I am familair with the circuit and know right where to look for the problem.  I will let eveyone know here what I found.  But my gut tells me I might just redesign the step start and just move forward.  We'll see.  Checking the circuit I see quite a few resistors that drop voltage and over time may be problematic.  I tend to take a more straight forward approach.  Stay tuned for more info as I have it. Lou

Hey Lou
That is great! Thanks for update to help Rocco get that beast going again. This is what Ham Radio is about. That is very nice of you to give a helping hand.
Fred


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on February 02, 2013, 12:07:39 PM
I would like to thank ALL of you who have helped and offered advise. Fred is right, this is why I got into this hobby. I have met so many great people and I can't thank this group enough.
 I am very happy to have Lou looking at my Titan for me. I know it will be in good hands and I am looking forward to hearing what Lou thinks when it arrives at his QTH.
 I agree that maybe the person I got it from knew there was a problem but I'm not going to point fingers. It is always possible that this is just one of those things that happen. I do know that the further I dug into it the more apprehensive I was getting. I respect the HV and just was not comfortable working on it. I am happy to send it off to Lou and get it fixed right.
  What really got me was how you guys offered advise and dug up schematics and put a lot of effort into helping me. Thank you all and If I can ever do anything for any of you, just send me a PM!

Thanks Again Guys,
Rocco


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 02, 2013, 01:12:58 PM
I pulled the updated schematic for this amp from a PDF that a K9 had posted to the web.  The older version of this amp used a 1.5A step start resistor and the newer one uses a 4A fuse.  This is why I asked about it in the beginning.  I don't like to critisize but I have my opinions.  Looking at the power supply schematic I see that the main control voltage is 28vdc mainly because the QSK vacuum relays use this voltage.  Then the control relays in the PS use 12vdc relays.  They don't have a seperate 12vdc supply so they use dropping resistors to suck up the other 16 volts.  Remember, these resistors burn up the wattage of the 16V drop so that the relays only see the 12v they want.  Over time these resistors age and can be problematic.  Personally I prefer using the proper relay so I don't have to use resistors to burn up unwanted power.  The thing is, the circuit will usually hold just fine for the warranty period of the amp, but 20 years down the road fatigue sets in and problems come up.  The power supply has a Hi/Lo plate voltage switch.  The switch activates a relay that switches between a secondary voltage of 550vac and 1010vac before the rectifier.  I am anxious to see what kind of relay they use for this. Not too many open frame relays are rated to switch 1KV or higher.  However Dentron routinely did this with their amps.  We'll see what happens.  Lou


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: K8AXW on February 02, 2013, 04:43:05 PM
Lou:  Guys like you are becoming fewer and fewer.  I can remember the day when...........


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 03, 2013, 03:11:33 AM
Lou:  Guys like you are becoming fewer and fewer.  I can remember the day when...........

Thanks,  well, I really don't like to see amps parted out when they can be fixed up.  At some point amps get so abused or hacked up that it is financially unwise to spend the money needed to revamp it.  These are the amps that should be parted out to serve that need.  In the case of Rocco's amp all it needs is some TLC to that power supply.  I understand the dilemma when one pays good money for an amp thinking all he needs to so is plug it in and go and then finds out it smokes.  Now that baragin price paid doesn't look so good anymore.  I have studied the schematic for this power supply and I already know what my plan of attack is on it.  Although it will cost Rocco a few bucks it will be reasonable and he can be assured it will be fixed.  I have been revitalizing older amps for a long time now and over the years I have obtained loads of repair parts that can be used in place of unavailable original parts. I will return with the end to this saga.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE2TR on February 04, 2013, 08:03:04 AM
Very sorry to hear about your amp, I had the same thing happen to my buddy's amp a week before the 1995 CQWW phone weekend, it turned out to be the power Xfmr, the primary shorted out. The same thing happened to three other ham's here on LI who bought the same amp but there amp's were under warranty my friends amp was one month outa warranty and TT said pay $450 for the repair. I would NEVER buy a TT product after that, even after hearing all the good reviews that some post on here about there products there service sucked IMO. The VP of TT at the time told me that if I had a GE fridge that was outa warranty by one month that they would charge me for a repair even of it had known issues with lets say the compressor, well I LOL in his face cause I had a 10 year old GE that the compressor did go, I called GE to order the part, they asked if I could give them the serial number and then told me that they would fix the fridge free cause it did have a known problem. I hope its not the Xfmr in your amp, if it is I would look around for an aftermarket one not a TT part.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on February 04, 2013, 06:25:14 PM
Lou and Rocco:

Sorry I have not been so responsive as of late. I had a major computer issue here, and am just getting everything restored back to normal.

Lou - I would love to hear what you find on this. I have some parts lying around here somewhere, which I use to keep the two 425's I use running. If you are need of parts let me know, and I will check to see what I have mounted on some of the scrap CCA's downstairs (if I can find them).

The only thing I would mention here is, if in fact you find the transformer secondary is the issue, then I would not be so quick to point the finger at the seller. I think we all know if this was the problem when the TITAN was sold, there would have been no quick fix that I could think of, which would allow it to run for as long as it did when Rocco got ahold of it. 

These are old amps, 90% of the problems I have seen with them has been power supply related!  I am pretty sure the problem is the softstart, but lets hope its a part on the CCA and not the transformer.

73

Rich, AJ3G


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on February 04, 2013, 06:41:52 PM
Hello All,
 I sent the Titan out today to Lou. I too am looking forward to his report.

Rich,
 THANK YOU!!!

 If the transformer is indeed bad, we will cross that bridge at that time. To be honest, I would most likely just get another one and fix it. In for a penny and all like that.......... I would hate to give up on the amp. I had one before and it ran very well for me. If you respect it and the tubes as well as the lack of grid protection, it should be a solid amp. (I hope!)

Thanks again everyone,

Rocco
WU2M

 


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 04, 2013, 07:53:06 PM
Well Guys, from what Rocco explained if I got his explanation correct is that he would turn the amp on and it would run for about 5 minutes.  After about 5 minutes of the amp just idleing the step start fuse would blow.  I looked at the schematic and the way I see it if the step start fuse blows after 5 minutes that means the step start relay (the one that shorts out the step start resistor) has to be dropping out.  You see, once the amp starts up 2 seconds after the switch is turned on the step start circuit including the step start fuse is out of the circuit.  The step start fuse is there in case there is a major overload in the amp.  It will blow before the step start resistor opens up.  If the amp starts up and runs OK for 5 minutes then the stepo start process is over with and it is out of the circuit.  For the fuse to blow that means the step start relay has to be dropping out for some reason.  Now the current is passing through the step start fuse to run the amp.  The fuse gets hot and lets go in 5 minutes.  I think the relay that cuts out the resistor in on the circuit board.  I saw some photos of the PS and it looks like that is a real wimpy relay that does that job.  It has to carry heavy current.  It could be the contact on that relay are toasted and it is letting go of the connection when it gets hot.  After all it is pretty old.  Ameritron amps use a larger relay than that and in time they go to.  It will be a fun job for me.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 06, 2013, 10:28:35 PM
Well Rocco's amp and PS arrived on Tuesday   I unpacked it tonight ( he did a great job of packing it) and I began troubleshooting it.  So far I found 3 shorted diodes in the rectifier string.  I think that could do a number on a 1.5amp fuse.  Rocco said that the last owner said he replaced the filter caps but I am suspect of that.  The capcitance was written on the bottom of the caps.  Does anyone know if Ten Tec did this?  Lou


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on February 07, 2013, 07:16:41 AM
...It was just sitting there in the stand by mode when I heard the fuse pop and the power went out.
 

All the more reason to suspect a powerline transient that popped a rectifier.


Yup. 

Thought so. 

She's in good hands now. 


73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: N3QE on February 07, 2013, 07:37:30 AM
Well Rocco's amp and PS arrived on Tuesday   I unpacked it tonight ( he did a great job of packing it) and I began troubleshooting it.  So far I found 3 shorted diodes in the rectifier string.  I think that could do a number on a 1.5amp fuse.  Rocco said that the last owner said he replaced the filter caps but I am suspect of that.  The capcitance was written on the bottom of the caps.  Does anyone know if Ten Tec did this?  Lou

This might be a silly question, but having done some linear amp maintenance myself on my own amp, and friends amps, over the years:

Why is it so common, for a simple supposedly reliable part like a rectifier diode, is often the problem?

Don't get me wrong, I'm actually pretty happy to help friends and be the tech wizard who opens up the amp and replaces a 5 cent part. By far the most common failure mode, is that it fails dead short. I'm not sure I can fix anything much more complicated than a linear DC supply or (on a good day) trace out a metering circuit. But this is 2013, I'm supposed to be flying to work in my hover car and jet pants, and still the most common failure mode is a shorted rectifier diode?


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on February 07, 2013, 07:57:32 AM
Well Rocco's amp and PS arrived on Tuesday   I unpacked it tonight ( he did a great job of packing it) and I began troubleshooting it.  So far I found 3 shorted diodes in the rectifier string.  I think that could do a number on a 1.5amp fuse.  Rocco said that the last owner said he replaced the filter caps but I am suspect of that.  The capcitance was written on the bottom of the caps.  Does anyone know if Ten Tec did this?  Lou

I do not think Ten Tec did this, as both of my PSU's do not have the Capacitance value written on the bottom of the capacitors.   


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 07, 2013, 08:53:32 AM
These caps are Mallory 400uf 450v with 525v surge.  They are the big long ones.  I think the new ones are short now.  Anyhow they might be good.  If someone bought them from Mouser lets say, Mouser I doubt would have marked them, the buyer would mark them?  Why...If he buys 8 of them he can't match them.  Just thinking out loud.  K1FO of our Lunar Link business did mark his caps and matched them as close as possible when installing them.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on February 07, 2013, 12:14:42 PM
Probably someone trying to troubleshoot at some time thought that marking the caps would make it easier.  I've seen all sorts of things like that over the years.  Like the one that had almost everything labeled underneath the chassis with laundry marking pen and even paper tape tabs around zitter and cap leads.  Pulled the bottom cover on the bench and the darn thing looked like the old fashioned hair up in curlers.  This is why it is good to have technicians at other benches in the same shop.  You've gotta have someone else around to call over and say, "get a load o' THIS!"    <grin>

So many are so wrapped up in the 'replace the caps' syndrome these days.  Perfectly good old Spragues lying in the trashcan with their leads clipped.  We get plenty of older and newer things in for repair these days where all the electrolytics were blanket replaced in an effort to fix symptoms that have nothing at all to do with filter caps.  And the reason we get them is that they still don't work.  A surprising number also have caps replaced backwards, or just plain wrong, too.  Following the easiest path, I suppose. 


73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: K2XT on February 07, 2013, 12:19:37 PM
If Lou was a cardiologist, and I had a heart attack, I would tell the ambulance driver to take me to Danbury Connecticut to be treated by the worlds best cardiologist.

"When your life depends on it, you want the best."


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KC4MOP on February 07, 2013, 02:09:34 PM
The Titan I had at one time had the original caps in the HV and it was thought that it was a good maintenance thing to shot gun them all. It wasn't that hard or outrageous in cost from Mouser.
I never heard of matching capacitors for an HV power supply.
There is a purpose for the equalizing resistors across the caps and diodes in that circuit.

http://audiosystemsgroup.com/Titan.pdf

Fred


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 10, 2013, 01:20:40 PM
Well folks the final word on Rocco's power supply problem is that it has a short between the primary and secondary.  It is a weird sort of thing, it appears the short goes through ground.  It's funny, if you leave off the ground from the wall socket all is ok.  Connect it and bang.  I isolated the transformer primary and secondary from the circuits and there is continuity between the primary and secondary windings.  I checked it against my 425 transformer and the same continuity is not there with mine.  SO we are looking at possiblities for a transformer replacement.  I told Rocco we can probably use an Ameritron Al-800H transformer.  It has the proper HV secondary and also has the filament winding.  I'll need a 20vac transformer to make the needed 28vdc.  Plenty of room in there to do the retrofit.  Yup, I know, a bad transformer is the worst of the problems.  So we will see what Rocco decides to do.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KO4NX on February 10, 2013, 03:03:33 PM
Yikes, that is not good news at all >:(

Has anyone looked into one of the Dahl replacements?  I was under the impression someone has taken over Dahl's designs, which at one time included a replacement 425 Transformer.

Rich


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W8JX on February 10, 2013, 03:13:34 PM
Yikes, that is not good news at all >:(

Has anyone looked into one of the Dahl replacements?  I was under the impression someone has taken over Dahl's designs, which at one time included a replacement 425 Transformer.

Rich

Harbach did but they as discontinuing them around 15th of this month. Said too costly to make a profit  in todays market. Looking for a buyer.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KA5N on February 10, 2013, 03:22:04 PM
I wonder if there is insulation rubbed off the wires of the two windings?   Might be difficult
to locate, but would be worth a try and cheaper than a new transformer.  Of course there
might be an internal short inside the transformer, or something sharp stabbing through the
insulation. 

Allen KA5N


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on February 10, 2013, 03:24:43 PM
I E-Mailed Harbach a couple of weeks ago and here is the response:

Hi Rocco,

The cost for a new Ten-Tec 425 transformer is $650.  We can rewind the old unit (assuming the cores are still good) for $350.

Factory lead time is approximately 4 weeks.

 Regards,

Jeff

I'm not sure what I am going to do yet. I will make some phone calls tomorrow and then make a decision.

Rocco



Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on February 10, 2013, 04:32:42 PM
...I told Rocco we can probably use an Ameritron Al-800H transformer.  It has the proper HV secondary and also has the filament winding.  I'll need a 20vac transformer to make the needed 28vdc.  Plenty of room in there to do the retrofit.  Yup, I know, a bad transformer is the worst of the problems.  So we will see what Rocco decides to do.


Hey Rocco,

What do you find to bad about this plan? 

If Rocco can convert to the rather readily available and likely lower cost 800H xfrmr, I'd say that would be an upgrade from the existing situation. 


73



Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 10, 2013, 04:35:07 PM
I wonder if there is insulation rubbed off the wires of the two windings?   Might be difficult
to locate, but would be worth a try and cheaper than a new transformer.  Of course there
might be an internal short inside the transformer, or something sharp stabbing through the
insulation. 

Allen KA5N

I inspected the wires best I can see.  It seemd like the short is inside the transformer.  I suppose it can be rewound.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on February 10, 2013, 05:04:13 PM
...I told Rocco we can probably use an Ameritron Al-800H transformer.  It has the proper HV secondary and also has the filament winding. I'll need a 20vac transformer to make the needed 28vdc.  Plenty of room in there to do the retrofit.  Yup, I know, a bad transformer is the worst of the problems.  So we will see what Rocco decides to do.


Hey Rocco,

What do you find to bad about this plan? 

If Rocco can convert to the rather readily available and likely lower cost 800H xfrmr, I'd say that would be an upgrade from the existing situation. 


73



I like to run digital modes. RTTY & SSTV and was concerned that maybe the Ameritron transformer would not be able to handle it.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W8JX on February 10, 2013, 06:56:30 PM
I wonder if there is insulation rubbed off the wires of the two windings?   Might be difficult
to locate, but would be worth a try and cheaper than a new transformer.  Of course there
might be an internal short inside the transformer, or something sharp stabbing through the
insulation. 

Allen KA5N

I inspected the wires best I can see.  It seemd like the short is inside the transformer.  I suppose it can be rewound.

A rewind would be about as good as new as possibly better depending on materials used.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on February 10, 2013, 07:38:09 PM
It has been my experience that a good rewinder often yields a better job than original. 


73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W8JX on February 10, 2013, 08:22:09 PM
It has been my experience that a good rewinder often yields a better job than original. 

Plus you know its fresh and has not maybe been on a shelf or warehouse 5 or 10 years or even more.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE3WD on February 11, 2013, 07:42:40 AM
Well, I know a fellow who rebuilds motors and xfrmrs, a rewinder, if you will, and he tells me that he can incorporate newer technology stuff onto an older technology core.  Things like better compounds than varnish or shellac, synthetics that won't be deteriorated by bacteria or chemical action over time, use of wiring that has better insulative properties than the plain old "varnish" coated stuff, etc. 

I don't know the particulars, but I do know that the xformers, motors, alternators, etc. that he rebuilds often actually do run "better than when new".  Cooler, sometimes he can even up the power ante a bit at the same time, things like that. 


73


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on February 11, 2013, 10:23:36 AM
Hello Everyone,
 I wanted to bring you all up to date. I have ordered a transformer from Ameritron which Lou is going to retrofit for me. Initially I was concerned because I like to play around with some digital modes. One of the things I enjoy from time to time is SSTV and I was concerned that I may have a problem sending images. Lou gave me some specs on what the transformer would do and it would work just fine. The AL 800H is rated at 1000 watts RTTY for 1/2 hour and I won't hit those kind of numbers. The modes I use are anywhere frome 1.5 to 4 minutes long so I see no problem going this route. I tend to run my amps on the easy side so I think this will work out just fine.
 I will update everyone soon.

Rocco
WU2M


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: K4RVN on February 11, 2013, 11:32:40 AM
I think you made a good decision Rocco and thanks for getting back as I have been following the thread with interest. Since the transformer suggested by Lou is in stock along with another small transformer, you should be troble free for years. I thought the price I found from Ameritron's site seemed reasonable. Good luck and enjoy your amp when Lou finishes with it.

Frank


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on February 11, 2013, 01:05:56 PM
I have no doubt that when I get the amp back from Lou, it will be better then it was when it left TenTec brand new! Lou went through and tested the RF deck and gave it a clean bill of health.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 11, 2013, 04:19:26 PM
For all following this, like Rocco said we'll be using an Ameritron Al-800H treansformer for his 425.  The Al-800H runs a pair of 3cx800's just like the 425 and so the Ameritron transformer already has the correct high voltage and filament voltage. We will need another small transformer for the signal voltage of 20vac and the rectifier is already on the TenTec PC board for that.  The Ameritron transformer has a heat sensor built into the transformer which if it overheats will break the keying line until the transformer cools down.  I'll probably hook that sensor up to a indicator that will alert Rocco if the transformer get hot and the sensor engages. I have already moved the step start resistor and fuse off the PC board.  I put in a fuse holder so the step start fuse can be replacxed externally.  This should be an interesting project doing the retrofit.  I have an Al-800H myuself as well as the 425 and they both make about the same amount of output power.  The Ameritron transformer runs about 200 or so more volts on the plates.  This should lower the grid current at higher power.  When this project is completed I will report back, in the meantime I will rip the transformer out of there and get ready for the transplant. Hmmmm, transplant.  Lou


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1NK on February 12, 2013, 09:01:46 AM
Thanks for keeping us up to date Lou. I never fail to learn something from your  posts & emails.

 Frank, W1NK


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 12, 2013, 04:06:53 PM
Thanks for keeping us up to date Lou. I never fail to learn something from your  posts & emails.

 Frank, W1NK

Hi Frank, How is your AL-811 running?  You ought to stop by when I am finished retrofitting the Ameritron transformer into the Ten Tec power supply.  I started planning for this project and I realized that I am going to have to rewire the rectifier board in the TT because the Ameritron transformer requires a doubler circuit.  The TT uses a FWB so I am going to have to change things around.  No big deal, just a bit more work.  This is like doing a transplant.  I ought to know ;D  Lou


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: KE2TR on February 16, 2013, 05:52:42 AM
I find this post interesting, using the AL800H xfmr is n excellent idea nd by the look of thing's TT wants to get outa the amp biz as well, maybe SS amp's might be there new way but Ameritron seem to kick there but in sale plus have many amp's on the table, maybe not the best amp's on the market but dm good value nd they seem to run and run for year's. W1QJ's xfmr swap is and excellent idea aand will keep that amp running for many year's to come, great job!
Jim


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 22, 2013, 09:03:21 PM
I suppose all those who had been watching this thread are wondering whatever became of poor Rocco's sick power supply.  Rocco had it packed up and ready to go to Tenn. back to Ten Tec.  I figured if it was something simple like a bad cap or a diode or some such simple thing, it would be easier and cheaper to ship it to me in Connecticut when Rocco is in upstate New York.  Well he did send it to me and I was doing the troubleshooting and found the same thing Rocco found, it was blowing the step start fuse right away.  Soon as you turn the amp on BAM.  A common occurrance in older power supplies is usually a shorted diode or a bad filter cap.  So I had to get down in there and check the diodes.  I did find 3 shorted diodes in one leg of the 4 in the FWB.  I replaced all 4 didoes in that leg.  I thought I had this problem put to bed.  After that I tried it once again, and again BAM!  The step start fuse blew again.  I had a full set of replacement type electrolytic caps, so I quickly removed all 8 and put in 8 new ones.  They are the screw in type so they are easy to change. tried it again.  BAM!  Well at this point I know it's not the power supply that is the problem, meaning the diodes and the caps.  The next thing I suspected was the transformer so I disconnected the secondary of the transformer from the recitifier and I ran just the transformer alone.  NO problem now.  The transformer secondary AC voltages right right on the money and there was no fireworks or humming or anything.  So I assumed the transformer was OK.  Back to the schematic again. Mulling it over I noticed they have a HI/LO relay on the PC board which switches the HV secondary between a 1010v winding and a 550v winding that are in series.  The common of the relay goes to the rectifier and the joined winding CT (if you will) goes to the relay NO and the bottom of the 550v winding goes to the NC contact on the relay.  This way there is a selection of HV of about 1800v and on hi 2400v.  When I looked at the relay being used for switching of HV AC like that I saw it was only rated at 250vac  I figured that perhaps somehow there might be carbon  traces inside that small relay that was arcing over the windings.  So I tried bypassing the relay and wiring the HV secondary seperate from the relay and straight to the rectifier.  I thought this is the last resort.  BAM!  same thing happened again.  So I finally figured it was time to see if I can bring this power supply up slowly on my Variac to see if I can hear some groaning or start to see some smoke from someplace by bypassing the fuses.  So I got my trusty Variac which I bought years ago from someone who pulled out the grounding pin on the plug, and began to see what I can find out by ramping the line voltage up slowly, bypassing the fuses.  So I went into the power supply and picked up the mains to the PC board and ran it to a cheater cord and hot wired the PS for testing.  I also hooked up my HV meter to the HV ouput so I could monitor the HV to see what is going on.  SO I plugged in my Variac and the amp cheater cord to the Variac and I slowly ramped up the HV.  It ramped up just fine no problem, all the way up to 1500v.  This was my 120v Variac, so I thought I would get my big 240v Variac and go all the way with it.  So I get my 240v Variac and plug that in to the wall and then the cheater cord into the Variac plug.  The Variac was on zero volts and looking at the HV meter I had hooked up I can see about 150vdc coming out.   So I'm thinking where is that voltage coming from to give me that little bit of HV on the meter.  I pull the plug out of the Variac and the HV droped to zero.  That's not good.  The other variac didn't show that voltage coming out on the high side.  This Variac has a good plug on it with a ground.  Ok, so I start ramping up the voltage with this Variac.  The transformer starts groaning.  It's not liking something. SO I unplugged the secondary of the transformer to the rectifier and the transformer ramps up fine with no rectifier in line.  Wait a minute the power supply looked OK with my other Variac(no ground on the plug) with this Variac (with ground on the plug) the transformer groans badly trying to make high voltage, remove the recitifier from the secondary and the transformer is OK by itself.  Ok now, I know everything was OK when I had no ground attached to the Variac, HV came up no problem up to 1500vdc.  Switch to the other Variac with a ground plug and GROAN right away.  Remove rectifier from tansformer Ok by itlsef.  AH OH...  I think we have something fishy with this transformer.  My Ten Tec 425 power supply was across the room in a box.  I pulled it out hooked it up to my big Variac and it ramped up to 2500vdc with no problem.  So now I start taking some continuity readings on the transformer and I see eveything looks ok on the primary and the secondary, but wait, I have some continuity between the primary and seconday.  Thats not good.  Ran the same test on my 425 transformer and no continuity at all between the primary and secondary.  So looks like we got a bad transformer here. YUP!  Somehow whatever kind of short there is in the transformer it involves ground somehow. I have heard of many old timers that used choke input filters on power supplies that blew out to ground.  They would mount the choke on rubber or something to insulate it from ground and put it back in business.  I'm not doing that!  SO I emailed Rocco and I gave him the bad news that the problem with his power supply is weirdly shorted transformer.  Told him we need another transformer.  Giving it some thought I recalled that my Ameritron Al-800H runs a pair of 3CX800's and is bascially the same kind of amp as the Ten tec 425.  I figured why couldn't I transplant a transformer for an Al-800H into this unit?  I looked at my transformer in my 800H and I see it can fit perfectly sideways.  Only thing it didn't have was a 20vac winding for the 28vdc needed for the control voltage on the Ten Tec.  So I found I coulod use a small 3A 20vac transformer for that and there was plenty of room to mount it.  I looked up the price of the AL-800H transformer and the Ameritron website said $247.00.  I figured that wasn't a bad price and asked Rocco to check it out.  I told him I thought out the whole plan to transplant the 800H transformer and the little transformer for control voltage.  I said I think I can make this work.  The major consideration was that the 800H transformer requires a doubler circuit rectifier.  The present PC board in the Ten Ten is wired for a FWB.  I told Rocco I would get out my Dremel tool (can't live without it) and I would go in there and cut the traces off the PC board that configures the 4 diode legs into a FWB.  I would then do a point to point wiring of the 4 legs into a doubler circuit and tap it acordingly with the new transformer.  I then modified the capacitor PC board for doubler service by drilling a hole in the trace that connects caps 4 and 5 and connect my other AC secondary in that hole and solder it to that mid point on the cap board.  I unsoldered the molex plug from the PC board and marked each hole on the underside of the PC board with what wires need to be put back in there.  So when I had possesion of all the parts I mounted the both transformers in their places and then began sorting out the wiring that neded to be soldered into the PC board.  One by one I solder each wire in the right hole on the PC board for it's purpose.  Once I had all the wires in place I put the PC board back in and screwed it down.  I had one more issue.  The Ten Tec transformer had a buck winding for the fan so that the fan had a fast and slow speed as slected by a switch on the PS.  The Ameritron transformer did not have this.  So instead of not giving Rocco the same choice he would have normally had I decided to insert a high power Dale 25 watt 300 ohm resistor in series with the fan.  I rewired the original fast/slow switch so that on fast speed it would short out the resistor and speed up the motor.  One last issue loomed.  The 800H transformer has a safety overload sensor built in it.  It is some sort of temperature sensor.  If the transformer heats up too much the normally closed sesor opens up and breaks the antenna relay line so that you can not transmit with the amp until the transformer cools down.  I didn't want to waste this feature since Rocco told me he was going to do SSTV with this amp.  I thought Rocco better know if the sensor says the transformer is too hot.  SO what I did was to use the 12vac winding on the transformer that Ameritron uses for control voltage and I rectified that voltage and made a small 12vdc supply.  I repurposed the Hi/Lo relay I removed from the circuit board that was no longer needed since the 800H transformer only allows one HV setting.  It is a 12vdc relay with NO/NC contacts.  I wired the pimary of the relay through the sensor that is NC to the +12vdc.  I then got beeper from Radio Shack that sounds like a truck back up signal.  I wired it through the NC contact on the relay through to the +12vdc supply.  Now, If the transformer over heats the sensor goes open, the relay loses power and drops out the beeper starts beeping until the transformer cools down and the relay kicks back in and stops the beeping.  So after all this I fired up the RF deck with the new power supply and the amp plays real nice.  HV is up to 2500v and the filament voltage is 13.2.  The amp makes an easy 1500 watts with 40 to 45 watts.  I ran the power up to 1800w and the grid current is only about 30ma.  The amp loads real smooth and plays great now.  Rocco is back in business.  I'll be sending the PS and amp back to him on Monday or Tuesday.  I am hoping he will take a photo and post it here of what the transplant looks like.  I suspect he will let us know how the amp works with this transformer when he does his SSTV.  This was a real neat project and I enjoyed the challange.
Lou W1QJ


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: K8AXW on February 23, 2013, 09:10:25 AM
Great job Lou!  I hope Rocco does post photos of this "transplant."  I  would enjoy seeing how this was done.

Al - K8AXW


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on February 23, 2013, 09:18:47 AM
Hi Everyone,
 
I will be posting pictures of the successful transplant next week when the amp arrives home. I am looking forward to getting it back and excited to get it hooked up and running! I can't even begin to thank everyone enough for all the advise given to me and especially to Lou for all the time and work he put in to get it up and running again.
 
 Pictures Soon!

73,
Rocco WU2M


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: K4RVN on February 23, 2013, 12:28:22 PM
Thanks for posting your methods and results Lou. I have been checking often for the final chapter of the repair. Glad to see a doer who was not afraid to improvise. I'll also be anxious to see the photos from Rocco. Now if I can just get a mic wired up for my old AF67 Multi Elmac I'll be happy for a time.

Frank


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on February 27, 2013, 02:39:18 PM
Hello Everyone,
 I got the Titan back from Lou today and all I can say is WOW! It works great. The work he did is great and it looks as though he took great care in his work. Everything is neat and clean and works like a charm. I am going to see if I can upload some pictures that I took. If not, I will upload them to a different site and post some links to them.
 I want to publicly thank Lou for all that he has done for me. Lou is a class act all the way! Thank you Lou. I am getting great reports with it already.
 Now off to figure out how to upload these pictures here.

73 Rocco


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 27, 2013, 05:38:10 PM
Thanks Rocco.  The guys are waiting to see what is going on with that power supply.  I'll answer any questions when we see the photos.  But on my last post I went through the whole procedure I took to deal with all the issues.  Basically you will just see a bunch of wires going from here to there.  The PC board is way down on the bottom of the amp and may not be seen very easily.  We have to see how the digitals show up.  Once I bench tested the amp with the new power supply rebuild I couldn't hear any sign of a groaning by the transformer when producing 1800 watts into my dummy load.  I am anxious to see some of Rocco's SSTV pictures when he gets that amp going on SSTV. 


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: K5MF on February 27, 2013, 06:41:36 PM
This is clearly an example of a craftsman at work.  Many of us grew up in the days of discrete components and true "field engineering" as was demonstrated here.  I was a data communications field engineer during the 80's and 90's and was quite sad when the industry (understandably) went to a board-swap or whole unit swap philosophy. I just felt like something was lost at that time. 

I worked on radar systems in the Navy and had a few opportunities to make a few Macgyver mods on them, but that equipment belonged to Uncle Sam and we had no choices at the time. I don't think I would have the nerve to try something like this on a relative stranger's equipment.  So my hats off to you and kudos for a job well done.  You obviously know what you are talking about.

I am curious though.  Do any of you with the contacts have any idea what it would have cost to have the transformer rewound.  I am not trying to second guess anyone, it is purely a curiosity question.  I have no idea what something like that would cost.   


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on February 27, 2013, 07:15:25 PM
I'm not sure how much it would cost to rewind it but it has to be at least what Rocco paid for the Ameritron transformer.  He paid $247.00 for it.  I had the transformer in about 4 days from Ameritron.  in the meantime I ordered a small signal transformer to provide the one voltage  the Ameritron did not have.  I did use the 12v supply voltage from the Ameritron to do some control work.  I repurposed the 12v relay Ten Tec used to switc the amp from hi/lo HV.  SInce the Ameritron tranny did not have a dual secondary there was no use for that relay so I removed it to make the Hi Temp alarm work if the trayy overheated.  I also used another 12v relay to short out a resistor I put in series with the fan to speed it up or slow it down. The originbal switch was on the power supply itself.  Kinda stupid because it is a remote power supply and most people would put it on the floor and off the operating table. If you wanted to slow the fan down when not transmiting you would have to get up and turn the switch under the table or some remote place.  I didn't think of it at first and had closed up the PS to send it back to Rocco.  Then it dawned on me that the switch on the amp to switc the hi/lo HV was not being used any longer, so I simply routed the relay coil that shorts the resistor out up through the wiring harness were it grounds out in the HI position.  When the switch is in hi the relay in the PS grounds out and shorts the resistor and the fan speeds up.  I told Rocco the only problem with the amp is that it's not mine.


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: WU2M on March 01, 2013, 07:21:45 PM
Hello Everyone,
 Here is a link to some pictures of the great work that Lou did for me. I'm sorry I didn't get them up sooner but I am a bit under the weather. Anyhow, the amp works real nice and makes plenty of power. I intend to put it through it's paces this weekend if I get feeling better.

http://s1352.beta.photobucket.com/user/helismash/library/

73, Rocco
WU2M


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: K4RVN on March 02, 2013, 10:07:42 AM
Clean looking power supply , thanks for posting photos and let us know how it performs this weekend on the air. You might need to put a schematic and note inside so some ham 20 years from now will know why it looks nothing like the TT schematic.

Frank


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: W1QJ on March 02, 2013, 12:48:20 PM
Clean looking power supply , thanks for posting photos and let us know how it performs this weekend on the air. You might need to put a schematic and note inside so some ham 20 years from now will know why it looks nothing like the TT schematic.

Frank

You are right Frank.  I really need to redraw a schematic  for Rocco, but I am so lousy at drawing I doubt he or anyone else can follow it.  My partner in LL has the program to draw schematics, maybe I can get him to do it on the computer.  That Ameritron transformer for $247.00 really works well and it doesn't fuss a bit when the amp makes 1800w output.  It loafs at 1500w output. 


Title: RE: Titan 425 Help (Blowing Fuses)
Post by: K8AXW on March 02, 2013, 05:00:13 PM
It has been said that a picture is worth 10k words.  These pictures say a lot more than that.  Great layout and wiring Lou.  Congrats on re-engineering a beautiful piece of equipment.

As for the cost of rewinding a transformer, based on what I've read in the past, $247.00 for a prewound transformer is a cheaper way to go.  It's only the huge transformers (broadcast to power distribution) that rewinding becomes cost effective.

Al - K8AXW