univox made lafayette LA 100 C?

[pinkjimiphoton]

hi folks,

a good friend got one of these and asked me to take a peek at it. he says as soon as the thing opens up, the tubes start glowing bright red.... i wanna check it out, nice looking amp, EVERY DANG CAP is an electrolytic

but i would feel a bit better if some kind person may have a schematic for the beast i could look at please? tried googling, but so far no dice.

output is 2 6973's, rec is a 6c4 i'm goona have to look to see what the other tubes are in it, most of 'em are 12ax7. i found a schematic that was close and sent it to him, but he apparently deleted it, and i guess it got deleted from my inbox too.

any help sincerely appreciated.

[52 Bill]

...EVERY DANG CAP is an electrolytic

That would be really unusual.

Maybe try and Google Univox U152. It has the same outputs and rectifier.

[pinkjimiphoton]

you're right 52 Bill, i was quite brain dead when i posted. they're mostly those tubular kinda waxy caps. i thought they were electro at a cursory glance in the dark, probably cuz my friend has weed way better than i am used to.
they all have the outer wrap marked, which i should have noticed. some are definitely bad, i'm reading voltage on about 10 of them where i wouldn't expect it to be (toward the ground side) and it has that peculiar horrible muted distortion of leaking dc... or at least in my limited experience with this stuff. i am no ee for sure, and quit messing with amps when my vision went south... but i wanna help my bud out, he's going thru some tough times and loves this little 15 watter. i dunno why, as it's never worked since he bought it, but still <g>

the tube compliment is 12ax7-7247-6av6-12ax7-6973x2 and 6c4A for the rec., i will google that univox, i think i've already looked at that schematic tho.

the weirdest thing for me is that the re's no negative bias like i'm used to seeing in most of the amps i've messed with, it's cathode biased i'm imagining. but all i've found coming off the K is a big freekin cap, someone put a 22uF 450v cap in there from k to ground and connected it to what appears to be the feedback resistor going back to what i think is the input to the driver stage. unfortunately, i don't have the chops to figure it out, it's been monkeyed with a lot.

when i first fire it up,it seems to work somewhat... then it's like watching the gain in a fuzz get choked off, andd the distortion increases ridiculously til the plates get red. so i'm thinking a biasing issue, but it doesn't appear the cathodes are connected to anything... i looked up the pinout. i gotta go revisit with some fresher eyes.

thanks for the reply, i'm on it. happy new years man!

[pinkjimiphoton]

bumping this to try and figure out how to get notifications in my email... sorry, couldn't figure out another way to do it!

[g1]

I'm not sure if the email notifications are working any more for thread subscriptions. Maybe someone can confirm?
Sometimes the cathode resistors are not mounted near the cathode bypass cap. Measure resistance across the cap., maybe there is a resistor in parallel somewhere.

[pinkjimiphoton]

hi g1, the "go advanced" function seems to have worked for the mail notifications.

i've looked, but so far, have not found a resisor in parallel with the cap, and it looks like there's nothing connected to the catthode at all. it's a mess. i haven't had a chance to get back to it yet, tho, so i may be wrong... thanks for the advice

it looks like they DO have a resistor coming from the k and cap node, but they have it connected to where the feedback resistor is hooked in. really weird. oi gotta gig tomorrow, so will check maybe monday... thanks again for the help and advice. rock on!