Traynor YGL3 Mark III tremolo + reverb question.

[tubeamptech]

First, the reverb works, but has a "ringing", almost "oscillation" over riding the signal. It has an Accutronics tank with no part # other than 1122 stamped on the chassis. Both input and output transducers measure 186 ohms DC. Typically you measure around that at one jack, and close to zero on the other. Everything else checks ok. I've never measured this on a tank, they typically work, or one of the transducers opens. I'm suspecting the tank, but what to replace with? It's a long tank, 2 springs.

The tremolo optoisolator on this amp is just a small square black box. I think it's toast. I measure ~4Meg ohms across the neon bulb. I have a new optoisolator on the way, the typical Fender style with the shrink tubing over it. My question is, should I add a couple of resistors to the optoisolator part of the cct. When comparing to a typical fender, I'm using a Bandmaster for comparison, there is a 100K in series with the bulb. I suspect to limit current. There is also a 10Meg ohm across the bulb and resistor. I want to make sure the bulb is running within proper parameters. Would you add these resistors?

[Chuck H]

Unfortunately there aren't specs for the reverb tank or the opto bug in the schematic. I can tell you that your reverb tank impedance is probably ok. That is not a typical Fender style reverb. It's capacitor coupled and the tube requires a much higher impedance than a transformer. That's no guarantee that tank is the EXACT right one, but certainly better than any stock, vintage spec Fender tank would be. I'm not sure what you mean by:

"...the reverb works, but has a "ringing", almost "oscillation" over riding the signal."

Is this a mechanical feedback/instability problem or is the reverb stable (doesn't oscillate on it's own) and this is like an effect when the two signals, wet and dry are joined?

I'll run some numbers on your reverb circuit and check some Accutronics pan specs and see if the impedances are ok. Unless someone else here that can do it off the top their head get's to it first

As far as the bug, which we have no specs for, I don't know if the readily available Fender bug is a drop in replacement. I do know there are vintage Traynor forums where these particulars get discussed. Since your answers are going to require someone with direct experience I would suggest that, if you don't get that here or find it by searching older posts or archives, you look into Traynor specific forums.

[tubeamptech]

The reverb doesn't "ring" when not playing, only with a signal applied. It decays at the same rate the signal does. The tank seems to be fairly old, but in good condition, so it may have been replaced at some point. It has a silver Accutronics label inside, underneath the floating assembly, but no part number. The label says it was made in Janesville, Wisconsin. Also found a number underneath. 7222.

[Chuck H]

It sounds like the reverb tank isn't behaving right because it's broken. Though I think it's pretty close in impedance. According to on line sources there are other schematics for that amp with the same reverb circuit that spec an Accutronics 4FB2B1C tank.

All I could find on the trem roach is that guys generally aren't real impressed with that amps trem even when it works and many go to the trouble of changing it to a BF Fender circuit and trem roach when the OEM roach fails.

[tubeamptech]

Right, I found that Accutronics number on another schematic as well. The problem is I couldn't find one in an initial search. I've sent an e-mail to Accutronics requesting info. It may be that after replacing the tank, the reverb will be less than desirable as well.

I think I will rewire the trem cct to BF specs, good idea.

[g1]

Is this a combo amp? If so, the first thing to try is pulling the tank out of the chassis away from the speakers, any change?
This tank is not transformer driven, but cap coupled, so the higher input impedance sounds right.
4FB tanks have approx. DC resistance of 200ohm input and 215ohm output so you are right in the ballpark.
Have you examined inside the tank for any visible problems?
Other things that may cause a ring are bad cathode bypass caps at the drive or return stages (C21 or C19).
Attached is the spec sheet for the PL-2H36 opto. Apparently the resistive part is far enough different from the Fender type that you do need to change to the Fender circuit.
Out of curiousity, I would contact Yorkville and ask what their fix is for that bug. They may have a sub that works, or a mod for the circuit.

[Alex R]

that driver pentode is likely to get microphonic.

[Enzo]

Yes, sounds like something on the drive side is microphonic, so the oscillation winds up going through the spring unit.

Your pan resistances sound fine, it is simply a high impedance input, contrasting to the low impedance that Fender selected.

[Chuck H]

The reverb doesn't "ring" when not playing, only with a signal applied. It decays at the same rate the signal does.

I interpreted this to mean the reverb effect doesn't even sound correct.

If the reverb is reverberating correctly, but there is a funny sound analogous to it, then what Enzo said. If the reverb isn't reverberating correctly the tank needs replacement anyway and there's nothing to lose.