Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: BlackCrowe604 on July 20, 2022, 03:56:27 am

Title: 1956 Supro Golden Holiday- Tremolo Not Working - Help!
Post by: BlackCrowe604 on July 20, 2022, 03:56:27 am

Hey Everyone,

I recently aquired an old Supro Golden Holiday. It is the same as the Valco 510-14 TH & TS circuits.

It appears to be all-original, works, and sounds great! Except the tremolo.

The tremolo is activated by a potentiometer with an on/off switch. When I switch it on, the signal fades (like the trem is about to start), but then it drops out and goes back to the normal signal level and stays there.

Couple of questions before I dig in:

1. The trem is driven by a 6SQ7 tube. There are old Sangamo Red caps, .05uf / .05uf / .02uf in the trem circuit. Might replacing these make a difference? I mean, they should ALL probably be replaced anyway. Any suggestions?

2. There is an additional 1/4in switchcraft jack on the top side of the chassis (this would be difficult to access with the amp assembled). I did not notice this jack until I took the amp apart. I am not sure it's function (it's not a speaker EXT jack) and doesn't seem to be listed... I've posted some photos of the mystery jack. Does anyone have an idea of what it's for?

(this jack is a shielded cable which connects to ground and a 270k resistor). Could this be what actually activates the trem?

Just thought I'd ask on here, it's too late at night for me to turn it up and try a shorting jack in there, and thought it might be good to know what the extra jack is for before I start changing caps.

Some photos attached. Note the front panel has a switching pot for the trem, and a "footswitch" in, but back corner of the chassis contains the additional jack that is noted on the schematic. Hopefully someone can explain! :D

Thanks Everyone!!

Title: Re: 1956 Supro Golden Holiday- Tremolo Not Working - Help!
Post by: BlackCrowe604 on July 20, 2022, 04:11:19 am

Here is marked up photo:

Title: Re: 1956 Supro Golden Holiday- Tremolo Not Working - Help!
Post by: sluckey on July 20, 2022, 04:56:35 am

No tremolo could be weak tube (try swapping V1 and V3 if you don't have a good spare), or low B+, or those three red caps.

The mystery jack is an Aux Input, maybe for phono, r2r line out, etc. See attached pic...

Title: Re: 1956 Supro Golden Holiday- Tremolo Not Working - Help!
Post by: BlackCrowe604 on July 20, 2022, 05:21:10 am

Thanks Sluckey, I will swap tubes, measure B+, and if those check out then I will throw new caps in the trem circuit and report back!

Thanks for unpretzeling the line in / phono jack, it makes sense!