68 Super Reverb doing very strange things

[TerryD]

I just got this off of Reverb.com.  Someone did beautiful work on this.  Red Tolex etc.  New caps, good speakers. Great soldering.  Sold to me by it's buyer, not the guy who did the work.

In any case, I play it for a while (10 minutes or so) then get what seems like a loss of power definitely coupled with distortion then no sound at all.

Turn it off for a while and I can play it again with normal sound but never sure for how long.  This scenario I've gone through a couple of times.  The amp is new to me.

Please don't say output transformer on the brink of destruction.

[HotBluePlates]

Look (and maybe smell?) for anything obviously overheating.

Then look/poke at all grounds; use the ol' chopstick.  Look for any other loose connections (wire, jacks, sockets) while you're at it.

Try plugging in a different speaker.  Mismatch is no issue as long as you don't blast 40w through a 10w speaker.

It would be handy if you could inject sound (CD player output?) through a coupling cap into the input of the phase inverter to divide & conquer troubleshooting the audio path.

[TerryD]

Thanks.  I thought I might be smelling something.  So it seems like the OT can't be ruled out just yet but could be something else. So, I have some hope.  I like the chop stick method.  I'll check the 4-10s wiring.

[robrob]

Do you have a spare preamp and power tube? Swap out one tube at a time and play and see if the problem goes away. A bad tube can cause your symptoms.

[TerryD]

I'll add that step.  Thanks