Bill Moore

Looking at the schematic, the 2M bass pots are in parallel with the caps C4, and C17.

Just noticed this thread, there are replacement caps available. https://www.amplifiedparts.com/products/capacitor-ce-mfg-160v-334747-f-electrolytic

I would use a 1A slow blow.

Is the "Hum Adjust" something like the Silverface Fenders used to balance voltage between the power tubes?

As one familiar with the 2 prong systems, I have an old 60's amp that I still play, but "someday" I'll convert it to a grounded plug! The drill is, hold guitar and brush back of hand across mic, get a tingle, reverse the plug!

I sure would be worried trying to fire it up without checking the power supply capacitors! If they are original, you could easily lose the PT!

The condition is rough, and if it doesn't work? That old of an amp really needs maintenance, and I would be hesitant to power it up without someone checking it out first. It may or not need tubes, but P/S caps for sure! Reverb price guide: https://reverb.com/p/gibson-ga-5-skylark

Measure the distance between the holes. in your amp.

There is a selection here, but I didn't see any brass handle mounts. https://www.tubesandmore.com/products/amplifier_parts_0?filters=974a277c276a974

I built my 5E3 initially using a JBL D-120, it sounded glorious, overdrive as a 5E3 will do, but it was really heavy! I installed a Weber 12A125A which I think sounds almost as good, but is a lot lighter!

Peter, if it sounds good don't change it! You need to worry about having too little reserve, not too much. I can attest that having an 18W Marshall plugged into a Marshall 4-12 cab with Celestions is a really glorious sound!

Never seen them before, but found this: https://www.canuckaudiomart.com/details/649006452-very_rare_and_collectable_gibson_pa_speakers/images/457871/

Check these out, if lucky one is the same, and you just need to replace the cap. https://www.tubesandmore.com/search/node/fuse holder

I just wonder, WHY? I bought a speaker cab from a fellow a few years ago that had staples holding the tolex inside the cab. After a year, I noticed wrinkles on the top and sides, I'll get around to recovering it someday, (but I'll use adhesive!)