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Author Topic: Titan 425 Help (Blowing Fuses)  (Read 16005 times)
W1QJ
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Posts: 1515




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« Reply #45 on: February 01, 2013, 12:50:56 AM »

Rocco, check your PM box for a message.  Lou
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KC4MOP
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Posts: 764




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« Reply #46 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
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W1QJ
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« Reply #47 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
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KC4MOP
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« Reply #48 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
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WU2M
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Posts: 29




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« Reply #49 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
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W1QJ
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« Reply #50 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
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K8AXW
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« Reply #51 on: February 02, 2013, 04:43:05 PM »

Lou:  Guys like you are becoming fewer and fewer.  I can remember the day when...........
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W1QJ
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« Reply #52 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.
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KE2TR
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Posts: 191




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« Reply #53 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.
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KO4NX
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Posts: 179




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« Reply #54 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
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WU2M
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Posts: 29




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« Reply #55 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

 
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W1QJ
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« Reply #56 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.
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W1QJ
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Posts: 1515




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« Reply #57 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
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KE3WD
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Posts: 5689




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« Reply #58 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
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N3QE
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Posts: 2421




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« Reply #59 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?
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