Just for completeness, here’s the original underside:
And with the new caps, many from Eks’ stash and a few from mine:
With all those in place, the firebottles lit up properly, the power tube plates remained dark, and it sounded great. The edge-lit engraved acrylic panel in the middle is a wonderful custom mod!
It’s in mint condition, with the original footswitch and a remote Echo speaker box with a pair of drivers:
It still has those original huge electrolytics, though. Eks says the best test comes after half an hour: if the cans remain cool, the leakage and ESR will be good enough.That’s the case, so we’re rolling with them. However, the amp has some residual hum that the Hum nulling pot can’t remove, plus a bit of noise, which means those ‘lytics probably hover at the bare minimum values required to keep it going.
I discovered (inadvertently, of course) that swapping the two identical 6D10 triple triode tubes killed the Vibrato oscillator. That triode would oscillate for a few seconds after the footswitch grounded the cathode, but one tube didn’t have enough gain to keep it going. More likely than not, the feedback resistors have increased in value, too. Swapping the 6D10s restored it to operating condition.
My Shop Assistant compared her tiny DSP Fender amp with this monster and concluded that DSP effects only sound good when you don’t have the original for comparison. Of course, you could lose that tiddly amp inside the Ampeg’s speaker case.