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Author Topic: Firing up a Heath SB-1000 amp for my first time - some issues?  (Read 2957 times)
KC1GCG
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Posts: 123




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« Reply #15 on: May 23, 2017, 07:17:32 PM »

Thanks again to all for the help and the warnings on my safety. Much appreciated! They are never wasted but even with my wanting to measure lethal voltages I did learn the hard way in college working on an AM Xmitter and getting probably a couple of KV from some caps - I can still feel that surge thru my arms just thinking about it 40 years later! So for anyone else reading this in the future heed these warnings. I'm lucky to be here - by most accounts I should have checked out that day 40+ years ago.
I also use a alligator clip lead with a resistor anytime I go into something that had power and use that to discharge any potential caps holding a "greeting" for me:) Even if its someplace I KNOW cannot have any nasty voltages I still "discharge" them remembering that zap decades ago.

Anyway.. Update is  I HATE it when things fix themselves.
I did the test as suggested with the anode disconnected and using SSB with no modulation and the plate current was zero with also  no movement on the grid current.  I then reconnected the anode and ta da the plate current is now 70ma! (as an FYI I also tried it with rtty/AM at zero power dialed n the Icom 7300 and it was also 70ma so apparently the Icom 7300 really does get it down to zero out and that was not what was causing it to be 140 ma yesterday) .  I guess it was either a loose connection on the anode (unlikely as I did go thru and tighten all screws before I even powered it up the first time) or maybe there was a bad solder joint on D401 as I pulled one side of it to test it and then re-soldered it. That seems like being incredibly lucky but.... any other ideas on what fixed it? . That's all I did . Or maybe my swinging the cat over the amp by its tail counterclockwise did appease the linear gods! Smiley
I do see an ever so small movement of the grid current meter when keying with the anode connected but not with it disconnected  (maybe 1 or 2 MA at most) on SSB no modulation. Is that anything to worry about or should I just try this puppy with a small amount of exciter into the amp and the amp into a dummy load and get this project moving?
Getting close......
John K1JRF
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KC1GCG
Member

Posts: 123




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« Reply #16 on: May 24, 2017, 05:38:19 PM »

Ok ok update update! No guts no glory so I fired it up and we have power!
Took it slow and got up to 57% drive and about 600w out. Reports are nice clean audio as I DO NOT want to be one of those dopes that sound like they are running a distorted guitar amp in a tin barrel......
I'll keep an eye on that plate current but hopefully it does not jump back up. Also guessing the small deflection on grid current with no drive is no biggy? I'll keep an eye on that also but if anyone has any concerns about that pls let me know.
Wish I had a better explanation on why its working but still thanks a ton for all the help. I did learn some stuff and that's most of the fun anyway.
Best regards
John K1JRF
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KC1GCG
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Posts: 123




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« Reply #17 on: May 24, 2017, 06:54:13 PM »

Well not perfect. Hopefully folks keep reading if not I'll post a new one.
Amp works on 15, 20 and 40 but no output power on 80. I do not have an antenna to check 160 at this time. Plate and grid goes up as I increase the exciter but nada on the power out. FYI I am also using on inline Diawa Watt meter.
Guessing I'll need to start with the switch... thinking maybe the coil? Visually all looks good fyi.
Thanks for any pointers.
Jhn K1JRF
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K4RVN
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Posts: 1185




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« Reply #18 on: May 24, 2017, 07:14:42 PM »

You may already have done this. I would suggest an old amp like that might benefit from spraying the band switch and others
with Deoxit D5. My AL 80 A once had no output on 40 meters and the spray cleared up that problem which has not returned after several years. You can buy it on the internet if interested. Rock the band switch back and forth a few times after spraying.

Frank
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K0CWO
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Posts: 465




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« Reply #19 on: May 25, 2017, 06:13:54 AM »

Fried 160/80 band switch positions on the SB-1000 is common and can be caused by not enough load on the load capacitor.  This may be the case with yours.  Google "SB-1000 band switch issues" and you will find plenty of info. 
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WB2WIK
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Posts: 21737




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« Reply #20 on: May 25, 2017, 08:10:28 AM »

"If your drive level really is "zero" (like SSB with mike keyed but no modulation), grid current should be zero.   Any grid current indicates something's wrong."

I don't agree with the above statement.  The no drive keyed plate current should be 50 to 80 mA as indicated in the manual.

My AL-80A which is almost identical shows 75 mA when keyed without drive.

You're discussing PLATE current.   I was discussing GRID current.    Grid current should be zero with no drive unless something's wrong with the metering circuit or the tube itself.

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K0CWO
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Posts: 465




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« Reply #21 on: May 25, 2017, 08:53:58 AM »

GCG was discussing plate current, but you are absolutely right.  I stand corrected.

73, k0cwo
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KC1GCG
Member

Posts: 123




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« Reply #22 on: May 25, 2017, 06:16:49 PM »

Progress folks....
Thanks for the tip for using contact cleaner on the switch but did not fix it. Visual inspection of the switch looks fine. I'd almost go as far as to say it looks new so maybe it's not the original.
I watched the switch make contact and move each contact piece to insure good physical contact and then buzzed it out and believe the switch is not the problem. I tested the doorknob 170PF for 80M and it tests out at 174pf.
I noticed a cut wire though while looking and looking and the fact that I missed it for days before says there could be more:) .
It is a black wire coming out of the tank ckt assembly that is behind the band switch. 3 wires some out , 2 are 2 conductor shielded and head off over to the PS/relay area (have not looked closely at that yet) and this black wire comes out with them and it is supposed to be connected to a ground lug on the plate cap assembly on the inside of the front panel. Its definitely been cut...not broken or burned.
So before I merrily go hooking it back up does anyone have any ideas on what may be behind that? I know there are a bunch of "mods" over the years for this amp, some good some not, and would like to figure out if I can why this was cut?
I don't see on the schematic what this could be short of maybe a wire connected to the shields of the two wires coming out of the tank ckt?
Outside of that causing my 80 meter problem, IF my switch diagnosis is correct, all that's really left are two caps and the coil for 80 meters correct? And I would guess if the caps were shorted I would see some indications on the plate/grid current so pointing towards the 80M coil being open? OR another cut wire or something open I have missed so far?
Got to go pick up my bride at the airport and will tackle this again in the AM if anyone has some more pointers for me.
Thanks
John K1JRF
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KC1GCG
Member

Posts: 123




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« Reply #23 on: May 25, 2017, 06:25:45 PM »

Correction me thinks:)
I said Tank ckt on the prior I should have said input filter assembly? Still learning this but I am referring to the assembly behind the band switch with the 6 adjustable coils.
Tnx
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N3QE
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Posts: 4748




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« Reply #24 on: May 26, 2017, 08:02:07 AM »

I noticed a cut wire though while looking and looking and the fact that I missed it for days before says there could be more:) .
It is a black wire coming out of the tank ckt assembly that is behind the band switch. 3 wires some out , 2 are 2 conductor shielded and head off over to the PS/relay area (have not looked closely at that yet) and this black wire comes out with them and it is supposed to be connected to a ground lug on the plate cap assembly on the inside of the front panel. Its definitely been cut...not broken or burned.

That is almost certainly the black wire that is cut to enable 10M ham operation. Reference below (from QST review of SB-1000!).



On your 80M quest - if you get plate current but no output power, when you apply input power, then the problem is almost certainly not the input network. Focus on the output network.

If you get no plate current when you apply input power on 80M, then yes investigate around the input networks and switching. Finding open inductor in the input network is easy with an ohmmeter. Try applying a signal at both top and bottom of 80M to see if you get any response at either end.
« Last Edit: May 26, 2017, 08:05:45 AM by N3QE » Logged
KC1GCG
Member

Posts: 123




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« Reply #25 on: May 29, 2017, 12:49:34 PM »

OK we have power on 80 and it was a PRSO issue! Happy old man today.
PRSO is a term from my old days as a field tech in the semiconductor business from a trip where I flew to China for a piece of down equipment and all I had to do was replace a fuse (in tech supports defense he did ask them over and over if the fuse was ok:) and it stands for Push Reset Slap Operator!
I did something similar in  not understanding the plate dial when I first got my Yaseu 101ZD but the short version is I had the plate pointer right on 80 and once I moved it a ways towards 40 tada I got power on 80! Not remembering that from my 101ZD can only be blamed on old age... ok maybe some other things from my youth catching up with me but I always knew that "bill" was going to have to be paid someday:)  I have now verified it works fine on 15, 20, 40 and 80. No antenna yet for 160 and what I have for 10M only gets down to about 2:1 swr with a tuner so I'll wait until I get something better before trying that band. Thanks for the info on my cut wire being the "enabler" for that.
Thank you all for all the help. Very very much.
I certainly know more about the workings of my amp due to this endeavor so something learned is never wasted.... unless I forget it:)
Best regards and I hope to work all of you someday soon... amp or not.
John K1JRF
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KM1H
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Posts: 2175




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« Reply #26 on: May 31, 2017, 05:12:54 PM »

Doncha just love no cost fixes?

In the USN we called your experience something that I cant repeat on here but I sure learned from them and became a damn good ET.

Carl
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