Hi,
I've recently come into possession of an old '65 Supro 16T guitar amp. It's completely original and I tried it briefly to see if it still worked. It powers up fine and plays well but has a slight background hum. I see it has an old Mallory FP capacitor in the power supply. Am I courting disaster powering this thing up? I haven't turned it on since I noticed the hum.
Edit: I can't find a Supro schematic but it's apparently the same as this Gretsch.
I've recently come into possession of an old '65 Supro 16T guitar amp. It's completely original and I tried it briefly to see if it still worked. It powers up fine and plays well but has a slight background hum. I see it has an old Mallory FP capacitor in the power supply. Am I courting disaster powering this thing up? I haven't turned it on since I noticed the hum.
Edit: I can't find a Supro schematic but it's apparently the same as this Gretsch.
Last edited:
yes you are courting disaster. Old amps have a predilection for exploding their electrolytic caps with messy, smelly and destructive results.
Do a quick search in here on resurrecting old amps - there are plenty of threads on the subject
Do a quick search in here on resurrecting old amps - there are plenty of threads on the subject
Just one other question,
I can't find the correct value 3 section FP cap (450v 20-10-10), is it ok to use a 525v 20-20-20 in it's place?
I can't find the correct value 3 section FP cap (450v 20-10-10), is it ok to use a 525v 20-20-20 in it's place?
Generally you can go up in voltage.
You should be careful raising the capacitance.
In this particular case you are OK. The 20uf in the Gretsch schematic is the first filter cap after the 5Y3 rectifier. You don't really want to raise this much, if at all, it will stress the 5Y3.
The other two should be OK to go from 10uf to 20uf.
You don't have to by a "Can cap" you can buy single smaller capacitors and install them inside the chassis. 😉
You should be careful raising the capacitance.
In this particular case you are OK. The 20uf in the Gretsch schematic is the first filter cap after the 5Y3 rectifier. You don't really want to raise this much, if at all, it will stress the 5Y3.
The other two should be OK to go from 10uf to 20uf.
You don't have to by a "Can cap" you can buy single smaller capacitors and install them inside the chassis. 😉
If that cap physically fits it should be OK. The preamp and tremolo are both cathode biased. If anything it should have a little less AC line hum than the original circuit. Be careful in there.
Thanks for the help, guys. I was thinking that an FP cap would be more "original"...though I guess I could leave the old one mounted anyway. It's a kinda desirable amp...the last one on ebay went for $700.
This is the interior: http://i247.photobucket.com/albums/gg159/rntlee/CIMG4850.jpg
Would I also need to replace the black and the orange cap? Not all the ceramics too I hope?
Sorry about all the dumb q's.
This is the interior: http://i247.photobucket.com/albums/gg159/rntlee/CIMG4850.jpg
Would I also need to replace the black and the orange cap? Not all the ceramics too I hope?
Sorry about all the dumb q's.
Yes give that orange and the black one a swap too, it also appears to be electrolytic.
Yes for resale value, keep the the old cap and tack the new caps underneath, or "restuff" the cap with three smaller ones.
The ceramics should be OK
Yes for resale value, keep the the old cap and tack the new caps underneath, or "restuff" the cap with three smaller ones.
The ceramics should be OK
- Status
- Not open for further replies.