i guess i wasnt 100% clear earlier: there is no relay - before this amp got to me, it was removed and someone actually rewired the bright switch to bridge the gap that the relay was supposed to bridge. but, like i said, as a result there's no way to turn the fuzz on. and on top of that the bright switch doesn't work.

so my challenge was finding a relay to replace the existing one but i wasn't quite what a suitable replacement would be.

enzo, how are you calculating what voltage the coil wants to see? just assuming a lowish coil resistance and voltage divider with R43 from there?

i'd be totally fine with dead-bug style - just wanted to make sure i'd have the right voltage relay.

bringing this one back from the dead

looks like the reed relay died whenever and someone had rewired the bright switch to bridge the gap. unfortunately, as a result, the fuzz does not work - cannot be switched into the signal.

ive tried snooping around online for a replacement relay but really no dice!

check out page 23 of the schematic

http://bmamps.com/Schematics/acoustic/Acoustic_260_Service_Manual.pdf

part number GB 651C 10?

cant find it - not sure what a good way to find a replacement would be - any advice appreciated thanks!!!

oh i see i see

about 415V on the plate - so 415 - 35 = 380. 380 * 0.05 = 19 watts dissipation.

and yeah just one triode before the PI so i guess it's supposed to be a lower key amp. and that's what it is!

thanks guys

oh yeah wrong here's scheme. here's the right one:

http://www.freeinfosociety.com/electronics/schematics/audio/ampegm15.pdf

couple questions about this amp, just wanna get some opinions and thoughts -

here's the scheme: http://www.unofficialampeg.com/schematics/j-12-b.gif

it was sounding kind of honky and felt like the tubes were running really hot. i measured and got ~32VDC at the cathodes of the power tubes, so 128 mA running through the 250 ohm cathode resistor - 64 mA per tube at idle. too hot!! right? i was hesitant to f!!* with the design - almost all original parts in here, BUT they were new JJ tubes and i figured well maybe they pull more current so itd be worth it to tame it down - i raised the cathode resistor 330 ohm now im about 50 mA per tube, still hot but seems a bit better. i know this is a tried and true ampeg design - does it make sense to try and tame it like i did?

other question: even with the amp turned up all the way, its really not as loud as 2 6L6s should be - i checked the output of the PI to the power tube grids and im only getting about 30Vp-p sine wave with volume all the way up. now the voltage at the cathodes, with the new 330 ohm resistor, is about 35VDC, so shouldnt i be getting closer to 70Vp-p at the power tube grids? or is this amp designed to not push the tubes all the way? i dont have any 6SL7 tubes around, but i tried rotating the three that are in the amp and there was no change. please disillusion me if im applying grid bias principles to a cathode bias amp and therefore barking up the wrong tree.

okay dialed the noise back a bit - there are some power supply trimmers in here that ended up being useful

last issue! repeats knob:

forget what i said in the last post - i was sleepy - so the repeats are just fed back from the output back into the input, building the signal onto itself. the repeats knob does seem to be making a bit of a difference, after some tweaking, but im guessing that cranked up to ten this thing should start to self-oscillate, right??

once again, its tough without the schematic. i can trace the signal leaving from the end of the tape section where it goes back to the input - this seems to be fine. it just doesnt seem to be quite enough of the signal to send it into oscillation. there is no gain stage after the repeats knob, it just takes the signal from the output and routes it back to the input of the tape section. maybe something around the repeats knob is biting off a big chunk of the signal so it can't get quite hefty enough to self-oscillate.

any thoughts?

k made some progress

replaced a couple of caps near the output of the tape section - cleaned everything - aligned the heads a bit better - sounding pretty good!

two main issues now:

1) unit is a bit noisy - sounds like 120hz hum - gotta scope it check it out

2) the 'repeats' knob doesnt seem to make a difference. im wondering how it works anyway...does it gradually disengage the erase head? the erase head does work - too good in fact - it erases the loop every time so i only ever get one repeat. sounds like a tricky fix. any hints?

damn not too easy to trace the signal - it kind of jumps between two boards - but i think i got at least part of the problem!

near the very end of the echo section - before the volume pot - i saw the signal wasnt making it through a tropical fish cap. replaced that cap and im getting a slight echo! it's pretty quiet, though. im wondering if other tropical fish caps in this thing might have to be replaced? its not new!

trying to get this old univox/LEM tape echo working

https://www.google.com/search?q=lembaby+schematic&biw=1600&bih=749&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjS0_myxb7NAhWIPCYKHS61D804ChD8BQgGKAE#imgrc=df06GrRwLy3VuM%3A

looks like that (mine's in a bit worse shape....)

the mixer works, passes signal. the tape loop spins and looks okay, but there is no effect. it's impossible to find a schematic so i am poking around in the dark a bit.

is there a simple way to measure that there is bias on the tape heads? can i just measure AC across the heads?

http://www.ebay.com/itm/TRIAD-Power-Transformer-Secondary-40-VAC-CT-2-4-or-6-Amp-Primary-115V-NOS-/161822278884?var=&hash=item25ad5c04e4:m:myHPVXn1DlFL1RUo_5aZ65g

good one?

this is a cheapo PT - maybe same brand as one that was recalled in the tiny terror?

at any rate - it's bad - not putting out anything.

any suggestions for a replacement?

http://music-electronics-forum.com/attachments/24395d1374795161-orange-cr35b-pwr.gif

alright trackd em down - just a few bad output transistor and they took the drivers with em.

replaced em - looking normal.

just need a new fuse - 15A in this amp. wow. thats high!

good call -

so those secondary windings should be very low resistance?

i unhooked one of the power amp modules and short gone. now to track it down....

trying to figure out this hartke LH1000 that's blowing fuses - my light bulb limiter tells me its a dead short somewhere - bulb goes on real bright real fast.

i started measuring around the power section, wondering if it's the PT. if i disconnect CN2 from the board, i read a short (<1 ohm) across any/all of the leads (black or red or red). seems like that part of the PT should NOT be shorted, correct?

here's a schematic:
http://music-electronics-forum.com/attachments/6758d1256749305-lh1000-v3.8.pdf

okeey

so i was a little misled because of the separate 12 and 24V supplies (like you).

after some scopin around, i saw that the waveform at C142 and C242, negative pole, looked not so good. kind of a really gnarly sine wave. i replaced those two and the voltages are looking better!

now the positive ones are still a bit iffy - not a good looking ripple. ill switch those out next and we'll see if problem solved!