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Post subject: Super Champ XD - Help fix!
Posted: Fri Mar 06, 2020 2:14 pm
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Joined: Fri Mar 06, 2020 2:05 pm
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Hey guys! I've been reading a lot on different forums--still looking for some direction here.

The amp powers up, no sound/hum/buzz through the speaker.
I replaced all the tubes. They glow.
I tested the speaker through a different amp--it works.
The line-out works with the preamp controls, which leads to to believe the problem is in the power side.
The channel light on the face works (I saw common similar problems where this didn't work).
The fuse looks fine.
I don't see anything looking burnt or blown on the control board.

So what's left? The transformer? I had trouble finding a transformer for this model, though I've heard they are more expensive than the repair is worth. I do have a multimeter, but I'm not sure where to start in testing it.

Thank you so much for your ideas.

It looks like there are two transformers as well. Not sure what's for what.


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Post subject: Re: Super Champ XD - Help fix!
Posted: Sun Mar 08, 2020 2:52 am
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Joined: Fri Feb 05, 2010 4:31 am
Posts: 14045
Location: Province de Québec, Canada
There are 4 fuses inside the amp , 3 of them may be the issue.
You must check these fuse with meter.

Also issue may come from many many parts; It is not a amp easy to work on. And for a newbie .......

Speaker output jack
Power supply components and/ or solder ; you need to check voltages inside the amp *
Output Power transformer ; read ohms at primary and secondary ; report
Power transformer ; you need to check voltage *
Speaker output jack

* lethal voltage inside tubes amp ; not a work for a newbie

Schematic and circuit board ;

https://www.thetubestore.com/lib/thetub ... ematic.pdf


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Post subject: Re: Super Champ XD - Help fix!
Posted: Sun Mar 08, 2020 10:07 am
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Joined: Thu Aug 07, 2014 3:25 pm
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You first get a "You might get shocked warning". So keep your fingers away from all metal parts or wear nitrile gloves.
TP 22 is the place to start measuring. Set your voltmeter to the 2-volt range and measure across R20 resistor. It should measure around .040 volts DC. This is your bias voltage and it tells you if the main tube stage is idling properly.
If it is zero, then your Power supply is not running or there are other problems. Set your voltmeter to the 1000 volts DC range and carefully measure across the main capacitors to see if there is high voltage on all three capacitors. It should measure 370-340 volts.
Then measure the voltage at the blue and brown wires coming out of the output transformer. Their voltage should be similar.
This will give you an idea of the performance of the main amp. I'm guessing you blew R47 or R79 that go between the big filter caps. Look for a small black spot on them.


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