Noise on a Panocordian Amp

[miltown]

Hey I have a real abor#$$ of an amp that I'm working on. It's made by Panocordian. Can't seem to find any info on amps from them just accordions. The problem is that it has a hum that when I touch the chassis it goes away but I take my finger off and it comes back. There is also a weird buzz that lasts for 15 sec. ( I timed it) then goes away then comes back. The buzz is very low level. This amp has been run over something awful. When I use the volume pot hum/buzz will change volume also when I pull the #2 12AX7 the buzz is gone. I have swapped 12AX7 w/ a new one to no avail. Pull #1 12AX7 and the buzz/hum is still there. Not looking to make this thing perfect would probable like to figure out the chassis issue most . The buzz I think my friend could live with because when the hum is gone the buzz is hardly audible even when turned all the way up. Any takers.

[olddawg]

Just for starters, do you have a 3 wire power cord with a chassis ground? Is the hum still there with the input grounded? What kind of rectifer does it have? How old are the filter caps?

[miltown]

Replacing the cord was the 1st thing I did. The filter caps are old. 1 is a mulit section can Sprague 4737 (couldn't find any info on it) and the another Sprague Atom that is newer. The rec. is a 5Y3 . The rec is putting out 380v. The plate voltage on the tube is 125v. Sorry my scope is down and I can't check the cap outputs w/ a scope. If I touch the either of the input jacks I get a loud buzz.

[Enzo]

No scope? Set your meter to AC volts and measure again those DC voltages. This will reveal the ripple voltage on that B+.

[miltown]

2 volts.

[Chuck H]

When I think of buzz I don't think ripple. I don't doubt that all the filters should be replaced but I'm thinking a leaky film cap or a ground fault between V1 and the input to V2.

[Gibsonman63]

For a schematic, search Panaramic and Sano or google accordian tube amps. I had a Panaramic on my bench earlier this year and had a hell of a time finding a schematic for a while. Then I saw that the foot pedal said "Sano" on it. Most of the schematics are similar. It didn't end up being a very loud amp for the size, but the reverb and vibrato sounded really good.

[miltown]

Yeah I actually spelled it wrong it's Pancordion Corp. They make accordians but I have seen no amp info. I saw one for sale. This amp is actually a screamer. The vibrato doesn't work. By the way Chuck the film caps are letting some DC thru. This thing was run over like I said, and it is very unstable between V1 and V2. You just put your hand over that area and noise noise noise. I definitely look act those suggestion Gibsonman. A schematic would be helpful but there is alot of "mods" and I use that term loosely. I think I see about 4 solder joints that look original that rest are someone's bastardization of solder joints. I should post a pic for your enjoyment. Give me a few moments and I will.

[miltown]

Here are some pics. Again caution it ain't pretty.

[Chuck H]

WooHoo. I'm RUNNIN' for a chance to work on that thing... Woah. Sorry dude.

Definitely replace leaky coupling caps or any other faulty components you detect before further evaluation. Otherwise it's all guess work.

[miltown]

Yeah I will be takin' my sweet time.