Fender Twin Turn On Thump

[Enzo]

how do my Superiors (that's you guys) charge for chasing dead-end clues in solving a problem....and still have a commercially viable business?

And the thing to keep in mind here is that those problems are the exceptions, not the rules. Most problems are simple: broken jack or pot, cracked solder joint, wires off something, bad tube. I charge an hour minimum for an amp, so if I find the bad tube or something in ten minutes, they still pay an hour labor. If all I did were unsolvable problems that took me weeks each, then I should get into a different business. The occasional zzinger is not the difference between a viable business and a failure.

Amp makes no sound:
Does the power light come on? Yes? Move on. No? Check fuse, switch, fuse holder, inrush limiter (if used), mains wiiring
Check speaker. if OK, then amp at fault. If speaker, you are already done, just get the new speaker and bolt it in.
DO ALL tube heaters light?
Is there ANY background sound or is it utterly silent?
Is there high voltage? Does it appear on every tube plate? Any plates stuck at B+ voltage. DO any non-grounded cathodes lack voltage?
Right there I have already diagnosed the majority of dead amps. And that really should take just a couple minutes.

Beyond that we start following signal. APply signal to the input, and see how far it gets in the circuit. Does it reach the power amp? Most amps have FX loops these days, and they are essentially the transfer point between preamp and power amp. Use those jacks as clues. Note it isn't until we get to these steps we really even need a schematic.

[christarak]

And the thing to keep in mind here is that those problems are the exceptions, not the rules. Most problems are simple: broken jack or pot, cracked solder joint, wires off something, bad tube. I charge an hour minimum for an amp, so if I find the bad tube or something in ten minutes, they still pay an hour labor. If all I did were unsolvable problems that took me weeks each, then I should get into a different business. The occasional zzinger is not the difference between a viable business and a failure.

Amp makes no sound:
Does the power light come on? Yes? Move on. No? Check fuse, switch, fuse holder, inrush limiter (if used), mains wiiring
Check speaker. if OK, then amp at fault. If speaker, you are already done, just get the new speaker and bolt it in.
DO ALL tube heaters light?
Is there ANY background sound or is it utterly silent?
Is there high voltage? Does it appear on every tube plate? Any plates stuck at B+ voltage. DO any non-grounded cathodes lack voltage?
Right there I have already diagnosed the majority of dead amps. And that really should take just a couple minutes.

Beyond that we start following signal. APply signal to the input, and see how far it gets in the circuit. Does it reach the power amp? Most amps have FX loops these days, and they are essentially the transfer point between preamp and power amp. Use those jacks as clues. Note it isn't until we get to these steps we really even need a schematic.

Thanks Enzo. Yes, I have those techniques in my kit bag, and it works for me most of the time. But sometimes I fall into the rabbit warren, and I think "can I make a business out of this".
I have a few other repairs to knock out, and then I will come back to this amp in a new thread. You may not have come across the Amp. It's called CremeTone 20. Made in China. 2xEL84's in Class A with neg feeback, and a solid state switchable gain stage. I have worked on a few of them and they punch way above their pay-grade in Tone.
Back soon
Chris

[Enzo]

But sometimes I fall into the rabbit warren, and I think "can I make a business out of this".

Don't define yourself by your failures. What matters is what you CAN accomplish. We ALL have repairs that get stuck on the bench. Every one of us. Patrick Mahomes doesn't always score a touchdown. You shake it off and move on. Wow, that sounds a lot more cornball now that I wrote it.

I won't go into it here, but I had a dumb little Laney amp hanging around my shop for TEN YEARS, and I would get it out, and just could not figure out the issue. And finally one day, I was struck by the faulty assumption I had been making. The amp had NEVER worked, the factory had installed two pots in each other's spots. But I got it.

[christarak]

Don't define yourself by your failures. What matters is what you CAN accomplish. We ALL have repairs that get stuck on the bench. Every one of us. Patrick Mahomes doesn't always score a touchdown. You shake it off and move on. Wow, that sounds a lot more cornball now that I wrote it.

I won't go into it here, but I had a dumb little Laney amp hanging around my shop for TEN YEARS, and I would get it out, and just could not figure out the issue. And finally one day, I was struck by the faulty assumption I had been making. The amp had NEVER worked, the factory had installed two pots in each other's spots. But I got it.

From the times you have helped me before, you may recall that I'm in Australia, so I hope I don't offend by saying I don't know Patrick (Sorry Mrs Mahomes, but I'm sure your cute little boy is very famous in America), but I certainly get the point of your advice. You have so many strings to your bow, Enzo. Counselling is one more. Thank you.

[Enzo]

OK...

Even Harry Kewell doesn't kick a goal every time.


Patrick Mahomes is a young phenomenon American football quarterback. he will be playing in the SUperbowl in the near future for the Kansas City team.

[Justin Thomas]

Jey christarak,

I was aiming tube swapping at 52bill, cuz it was the only thing I didn't see in his "list of things I tried." �� Though, he's a lot more knowledgeable than me, so I would have expected it. But sometimes even the best of us forget the obvious...

Justin

[christarak]

Jey christarak,

I was aiming tube swapping at 52bill, cuz it was the only thing I didn't see in his "list of things I tried." �� Though, he's a lot more knowledgeable than me, so I would have expected it. But sometimes even the best of us forget the obvious...

Justin

Too true Justin. And your comment was valid...even when not meant for me.

[christarak]

OK...

Even Harry Kewell doesn't kick a goal every time.

AHA! Now I get it

[Enzo]

(Good, I hoped he wasn't a goalie)

[52 Bill]

Jey christarak,

I was aiming tube swapping at 52bill, cuz it was the only thing I didn't see in his "list of things I tried." �� Though, he's a lot more knowledgeable than me, so I would have expected it. But sometimes even the best of us forget the obvious...

Justin

The list of things in post #8 were the things that I tried after asking here for help. Before that I went through the normal things that you try to fix this problem, like cleaning/replacing the standby switch, putting a cap across the switch terminals, changing tubes, etc., etc.