vintage Traynor ygl-3 mark 3 reverb problem

[jp-90]

Just picked this amp up--it sounds great but the reverb is out and I'm hoping that between the ptp wiring, the included schematic and a little forum help i can fix it on my own.

From what I can tell, the reverb recovery side of the pan is fine. With the amp on, shaking the pan results in the usual clanging about that one would expect. This makes me assume it's a problem in the drive side. The reverb is driven by an EL 84. The previous owner had a 12ax7 in the EL 84 socket, so i swapped it for the correct tube, but still nothing. So, where do i go from there? Any obvious internal failures that would result from a 12ax7 being plugged into an EL 84 socket? Is it time for me to start checking every component around the reverb drive?

THANKS.

[52 Bill]

Is it time for me to start checking every component around the reverb drive?

Well, maybe. Did you check the input coil of the reverb tank? Is the tank driven by a transformer or via a capacitor?

[jp-90]

unless there's some sort of transformer in the reverb tank, the signal seems to leave the el 84 and pass through a capacitor before going to the tank.

i found a schem online but it's a little different from mine. I'll try to upload a photo of the schematic that came with the amp in case that helps.

THANKS.

ok, found it - http://www.crumplezone.co.uk/burt/ge...GL3_3A_Mk3.gif that should get you to the schematic i'm working off of. Thanks for the help!

[g1]

Can we assume the 12AX7 wasn't put there as a result of the circuit being modified?.
If it's not a mod the components I would check first would be the tank input coil, the 10watt 15K plate resistor (R46) the 270R cathode resistor (R45) and capacitors C22 and C23. Not much else on the input side other than C21 and R44, might as well check them too.

[jp-90]

PROGRESS!

Reverb is a WORKING again! Thanks a ton for the help. The problem WAS at the input coil. I had looked inside the pan twice already, but checked again after the comments--the tiny green wire connected to the positive tip of the input line had been pulled off of the input jack. Easy fix.

So, the amp still has two other tiny problems. One is such an infrequent and hard to describe sound I won't bother with it (the whole thing probably needs new tubes which could rectify this weird sound). The other problem, however, is the tremelo. When the tremelo is on and i'm not playing there is a faint sound, almost like a chewing sound coming from the amp (not the usual white noise whoosh). Could this be fixed with a new tube? Do I need to replace the tremelo "bug"? I honestly don't know much about how this tremelo works (photocell?)---it's much less intuitive to me than reverb so i have no idea where to start on troubleshooting.

Thanks for the advice. the reverb is sounding great.

[52 Bill]

Glad to hear that the reverb is working.

You should always check things like reverb tank coils and fuses with an ohmmeter, as visual checks can be misleading.

I don't understand the "chewing" sound, is it affected by the speed or depth controls?

The trem works just like a blackface Fender circuit, the output signal from the 2nd channel is shunted to ground via the photocell in the bug. The depth control regulates the amount of signal that is sent through the photocell.

[jp-90]

You're right. I learned my lesson on the visual checks.

As for the tremelo sound: it is affected by the speed knob (it follows the trem rate) but not the intensity (depth) knob. I said a chewing sound, but maybe a rubber squeaking sound would better describe it. Again, the trem works, there's just this sound audible when not playing. Could I need a new bug? I changed out the tremolo tube and that had no effect. something else?

[52 Bill]

If you mean a sort of chirping sound, I doubt that the bug would cause that.

I'd be more inclined to look at the filter cap for that node of the power supply. For that matter are all of the filter caps original to the amp?

[jp-90]

My guess is that everything inside is original. The only quirk is that there's a penciled in (on the schematic) line going to ground in one part of the amp, and in the corresponding area of the amp i can see two non-original snipped wires--but this probably isn't my problem.

So yeah, i think all caps are original to 1973, but i'm new to electronics and thus not too sure. I was excited to get this relatively inexpensive, hand-wired amp to learn on.

Could you tell me which caps are the filter caps based on the schematic? I have a multimeter to test capacitance and have read up on the safety requirements, so hopefully i could weed out the problem. THANKS for the help.

[52 Bill]

The filter caps on your amp are the large aluminum cans mounted on the chassis, C13 and C36 as well as one separate cap C26.

Make sure the caps have been discharged before you start messing with them, as they will store enough energy to do you bodily harm.

[trood]

Here's one since we're now talking tremolo. My Mk3 is loosing audio as I turn up the intensity control, completely gone when all the way up. I've subbed V3 and checked for shorted caps and open resistors, there are some high ohms so the circuit might be fooling my meter. The one thing I have seen is pin 8 of V3 should be 35V but is 10V. Any ideas? No broken wires or obvious burned parts. Oh, it is the opto circuit not the variable bias type.

[52 Bill]

Trood:
From what you describe, the photocell part of the optoisolator sounds suspect. If it has shorted, you will just be grounding out the signal as you turn up the intensity control. Check its resistance and also check the wiring from the control.

[mondo]

In my ygl3a from 1972 the filter caps are inside with the wiring. They are the big yellow sticks of dynamite made by Mallory. I will be replacing mine asap as they are 40 years old and could be a liability. Do heed the advice on messing around with the high voltages stored in these. There are some youtube tutorials on the correct methods of discharging capacitors. Caps can spontaneously re-charge themselves too so draining voltages is important but also remember to keep them drained with the discharger device.