Super Champ XD problems

DrBGood

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It's basically between the preamp and power amp sections. It's necessary in a push-pull amp, as it takes the single input signal and divides it into two outputs (one for each tube), one in the original phase and one that's 180-degrees out of phase, each signal going to one of the output tubes. It's one of the most important parts of the whole circuit.
Ahhh ... now I get it.

NOT ...

That's like Chinese to me. I'd have to have someone by me, with an open amp and a laser pointer, to explain every bit and their function, just for me to START to understand how it all works. All I know for now is, when an amp is working good, I only have to plug in my guitar and twist a few knobs to get a smile on my face.
 

67plexi

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Chinese the answer parts anyway it's a sad world we live in now. I had a China Vox AC30 on my bench it cost more to repair than to buy new.
 

jtcnj

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DR. if you are interested in learning, just for kicks or whatever, maybe not not fix this problem, over at TDPRI there is a Shock Bros DIY tube amps and also a Tube amps sub forum. It is where I cut my teeth on this. There are numerous links to basic through advanced sources. There are other good sites but thats where I was anyway being a Tele addict as well.

A start is a basic single ended Class A design - like the Fender 5F1 Champ to start learning. I went all in and built one from scratch, no kit. But, just reading up and learning is good too.

I think I learned more of the basics in a coherent way, that I have built on, from Dave Hunters Tube Amp Handbook which I got used for about $23. This really got me on the path to valve enlightenment. I'm not there, but I'm on the path.

Like I said there are tons of links - some of the most helpful once you get some basics down are the ones to parts of Merlin Blencowe's books. I'm re-reading some of those pages myself; more of the details make more sense to me now.
 

paul-e-mann

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Easy things to try:
Try a different speaker cable? Clean all your jacks and pots with Deoxit? Try a different guitar? Try a different guitar cable? Reseat tubes and clean tube sockets with Deoxit?
 

DrBGood

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Easy things to try:
Try a different speaker cable? Clean all your jacks and pots with Deoxit? Try a different guitar? Try a different guitar cable? Reseat tubes and clean tube sockets with Deoxit?
It isn't the guitars or guitar cables, they work great on other amps.
Whatever the settings, clean channel, effect channel, external speaker with new cable, same result. If there is loudness enough to make the chassis vibrate, either more bass or more volume, the distortion happens. It is a matter of making things loud enough so the chassis vibrates, so in my book it must be a bad weld or connexion in there. Anyways, it's off to the tech for now.

Thanks for all the suggestions, it allowed me to at least eliminate things I could have easily solved myself.
 

DrBGood

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Back from the tech. Says it has a weird problem, can't (or won't) fix a Chinese board. Big help !
I'll find another tech.

EDIT: I just tried the external cabinet beside the amp, not under so the chassis won't get vibrations from the speaker. Problem still there, no change.
 

jtcnj

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YESSSSSSSSSS!!!!

tumblr_neqwkbYwt91sgl0ajo1_500.gif
 

TonyCbus

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Found a Fender authorised tech who fixed it in no time. Replaced the 12AX7 if I remember well and did some clean-up.
$20 and a happy camper. This thing is really versatile. Love it more and more !
Hi, I am having the same problem that you described here. Was the fix to simply replace the 12AX7 or when you say Clean up, do you mean cleaning up some of the soldering work? Thanks
 

DrBGood

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Hi, I am having the same problem that you described here. Was the fix to simply replace the 12AX7 or when you say Clean up, do you mean cleaning up some of the soldering work? Thanks
Phew ... that was 5½ years ago. I didn't even remember I've had a problem with that amp. I have two of them and nothing but good tones since then.

Sorry I can't help more.
 

TonyCbus

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Phew ... that was 5½ years ago. I didn't even remember I've had a problem with that amp. I have two of them and nothing but good tones since then.

Sorry I can't help more.
Thanks anyway, I’ll try the 12AX7 replacement first since it’s the cheapest route. Then maybe try to replace the 2 6V6 tubes next since they all are the originals.
 

TonyCbus

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I swapped out the 12AX7 with an Electro Harmonix 12AX7 and it fixed the problem. I didn’t love the tone though, so I switched that out for a Groove Tubes 12AX7 and it sounds pretty good. Now I’m in the process of ordering another 12AX7 tube to see if I like the tone even better. I’ve created a new problem with wanting to try different 12AX7s to see what sounds the best.
 


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