One of Kegger's Old Amps Needs Repairs

whell

whell

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Some of you might remember this one, since it made an appearance at an AK Fest or two:

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Paul's description:
Parallel Single Ended Ultra Linear 6LR8 (taken to the extreme version compactron amp)

I bought this amp from Paul a few years ago and love it. However, when I got back from vacation and fired it up today, I'm getting sound from only the right channel.

Paul's loss was keenly felt and he left a great legacy here. I've enjoyed this since hearing it years ago for the first time. However, I'm no technician and this is certainly a one of a kind unit. So, now that it's having issues and Paul is making tube amps for the angels, I don't know where to turn to have it diagnosed and fixed. There's a local shop that I've used before and I know the guy personally owns tube gear, but I don't know if he'd repair someone's unique home made gear.

So, thought I'd start here and see what some of you guys think. Not sure if this is the right place for this question so mods please advise if this needs to be posted elsewhere.

Oh, here's what I've tried on my own, which at least covers the basics:

Checked for faulty interconnects
Checked speaker connections
Checked upstream gear for faulty connections / issues

Checking these items allowed for isolating the amp as the issue.

Thanks!
 
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Try swapping tubes left for right channel. That will help determine if it's the tubes or something in the circuit.
 
When doing the swap, re-tension all the sockets. A small flat screwdriver or awl carefully inserted between the socket body and metal fingers and a slight twist (doesn't take much) will do the job. That should be a regular tweak anyway.

I'd also pop the bottom and look for loose connections or maybe a burned component. There's probably a resistor on each power tube to ground that's intended to be sacrificial and protect the more expensive bits. If one looks burned, replace it and keep your fingers crossed.

Any good with a soldering iron? Next step is usually to repoint all the connections on the dead channel. This can work wonders as solder can crack and go open from all the hot/cold cycles.

Luck wit it, eh ...
 
Also, check for any fuses underneath, but mind that hazardous high voltages are in play, and a shock hazard may still exist long after turnoff.
 
All tubes are lit. If that's the case that would rule out a fuse issue, correct?

Swapped tubes one at a time from one side to another but the same side is still not producing sound. I'll try the retensioning suggestion next. Probably need to stop short of opening it up. Not in my comfort zone, so I don't want to risk making things worse.

Thanks guys.
 
Well that pretty much seals it that its something in the circuit. Yes try retensioning, but I expect its something underneath the hood at this point.
 
I'm having similar issues with some of Paul's stuff I'm selling for the family and here's my plan. First get a schematic; Paul was generous about posting them so it may be buried here someplace on AK.
Second, given one channel works, it seems one could work backwards from the outputs taking meter readings one both channels until you find the point where they match, as that would intuitively ID the funky component. Or work from the power tranny out and look/stop when the readings don't match. I'd like to be more help, but I'm already overwhelmed with his estate.

That may be beyond your comfort level, but I would guess your tech could take that approach. The fact that one channel works really is a blessing as you can use it to mirror the funky one for diagnostics.

Good luck!
 
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Andyman said:
I'm having similar issues with some of Paul's stuff I'm selling for the family and here's my plan. First get a schematic; Paul was generous about posting them so it may be buried here someplace on AK.
Second, given one channel works, it seems one could work backwards from the outputs taking meter readings one both channels until you find the point where they match, as that would intuitively ID the funky component. Or work from the power tranny out and look/stop when the readings don't match. I'd like to be more help, but I'm already overwhelmed with his estate.

That may be beyond your comfort level, but I would guess your tech could take that approach. The fact that one channel works really is a blessing as you can use it to mirror the funky one for diagnostics.

Good luck!
Click to expand...

Yep.
 
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