# YGL3A misbehaving tremolo



## Patrice Brousseau (Aug 12, 2020)

Good evening,

The tremolo circuit is acting up on my YGL3: the more time it’s used, the less it works.

Yesterday, it was starting at 2 - 3 on the intensity knob and the tremolo was deep and good.

Today, after several hours of use, it barely works at 10. I guess, that tomorrow, at cold, it’ll be back to normal.

It looks that something drifts a lot when the amp is running for a while...?

The 125 bypass cap on the 12AX7 was already replaced when I got the amp. One 100 uf and one 25uf in parallel were used.

Anyway, I plan to:

swap another 12AX7 (even if I already replaced the original 12AX7...);
if no improvement in the behavior, replace all caps and resistors in the tremolo circuit;
if no improvement, replacement of the optocoupler...

Could the resistors in the trem circuit or even the trio of ceramic caps (.01 - .01 - .02) be responsible of this?

If it’s the optocoupler, what would be a modern substitute for the PL-2H36 part?

It’s rated at 320 volts, resistance varying from 400 ohms (on) to 50 megohms (dark).

Data sheet attached

Thanks,

Patrice


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## Patrice Brousseau (Aug 12, 2020)

Schematic attached, if needed... Mine is the one with the internal adjustable 2.2meg trimmer.


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## Jim Jones (Sep 18, 2006)

If any of the resistors or caps in the circuit have drifted significantly the oscillator won’t oscillate so it’s definitely worth measuring them.


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## Paul Running (Apr 12, 2020)

It could be a temperature sensitive issue. Freeze Mist, may isolate the problem component. When it begins to act up, spray the component(s) suspected. Carbon comp resistors will drift.


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## Patrice Brousseau (Aug 12, 2020)

@Jim Jones : I have no equipment to measure the caps, so I’ll replace them I think.

@Paul Running : carbon comps will be replaced too once in there...

Kind of a shotgun approach but at least it’ll tell me if the opto coupler is still good (probably as it works ok when cold but anything could happen after 47 years  )

I’ve already e-mailed Mr Guy Beresford to inquire about a modern substitute for the opto-coupler, in case it’s my last resort.

If no substitute in case of dying opto-coupler, I’ll plan a conversion to AB763 tremolo circuit as the Fender bug is easily available.

I hope I won’t have to go this route and that caps/resistors replacement (or tube swap/socket cleaning) will be the ticket!

Thanks guys!


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## Paul Running (Apr 12, 2020)

Patrice Brousseau said:


> If no substitute in case of dying opto-coupler, I’ll plan a conversion to AB763 tremolo circuit as the Fender bug is easily available.


Some info on the Fender tremolo.


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## jb welder (Sep 14, 2010)

Try tube first, then caps. (assuming resistors check ok)
You can't trust the cathode cap someone else put in, and yes, those ceramics could cause a problem like this.


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## Paul Running (Apr 12, 2020)

Patrice Brousseau said:


> If it’s the optocoupler, what would be a modern substitute for the PL-2H36 part?


Build your own coupler, here's the basic components: piece of 1" PVC pipe, photo-cell from oil burner, flame sensor and a light source. The light source is an interesting component...this one is a modified LED, incandescent will produce a smooth sounding tremolo...the light source is the key to a desired tremolo action.


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## Patrice Brousseau (Aug 12, 2020)

I’ve ordered a Fender roach from NextGen just in case caps and resistors swap makes no change.

1 - replace every part of the tremolo circuit except opto coupler;
2- if unsuccessful, Fender roach in place of the OEM;
3- if roach doesn’t work with Traynor circuit, going to mod to Fender circuit.


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## jb welder (Sep 14, 2010)

Patrice Brousseau said:


> 2- if unsuccessful, Fender roach in place of the OEM;
> 3- if roach doesn’t work with Traynor circuit, going to mod to Fender circuit.


Yes, I'm pretty sure if you want to use the Fender opto you will have to change to the Fender circuit. Others have tried the Fender part in the Traynor circuit and it doesn't work right. Not a difficult change though.


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## Patrice Brousseau (Aug 12, 2020)

BTW, tube swap did nothing. I tried three different ones with the same result: tremolo loosing intensity after using using it for a while.


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## Patrice Brousseau (Aug 12, 2020)

jb welder said:


> Yes, I'm pretty sure if you want to use the Fender opto you will have to change to the Fender circuit. Others have tried the Fender part in the Traynor circuit and it doesn't work right. Not a difficult change though.


I’m just not 100 percent certain that I would have to replace the two pots? Mine are 250k RA and 4 meg RA.

Fender is 50k and 3 megs.


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## Patrice Brousseau (Aug 12, 2020)




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## jb welder (Sep 14, 2010)

Patrice Brousseau said:


> I’m just not 100 percent certain that I would have to replace the two pots? Mine are 250k RA and 4 meg RA.
> 
> Fender is 50k and 3 megs.


I would try with the Traynor pots first.


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## Patrice Brousseau (Aug 12, 2020)

Thanks,

If time permits, tomorrow will be swap parts day...


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## Patrice Brousseau (Aug 12, 2020)

Ok,


R8, 52, 53, 54, 55, 56, 57 and 58 replaced;
C14, 15,16 and 37 replaced;
Deoxited intensity pot and 2.2M trimmer.

It's now playing some music on my iPod and I regularly verify if the tremolo still works. I'll let it cook like this the evening. If it remains stable, good!

In the case the answer is no: modification to AB673 tremolo ckt as I already received the roach from NextGen.


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## Patrice Brousseau (Aug 12, 2020)

Oh well...

After an hour approximately, same thing as usual: decrease of tremolo...

So, I tried the roach as is, nothing, it doesn’t work.

I’ve then decided to copy the Fender circuit, not without a bunch of miswiring at first (plate reversed with cathode, speed pot connected at the wrong spot...).

Finally got the circuit correct with voltages corresponding to schematic... but no oscillation at all. It was 3AM and I was in a dead end...

Thinking about it, I suspect that the kick start voltage could be the problem:

- I have -46v but schematic calls for -55.

I’ll try to tap the negative voltage before the bias pot with appropriate resistor value. -83v would a bit higher I think...


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## Paul Running (Apr 12, 2020)

If you suspect the start cct., you could momentarily ground the grid of the osc. (the pink-dot in the diagram below):


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## jb welder (Sep 14, 2010)

Are you using the footswitch or not? If not, is it a switching jack and is the switch contact good?


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## Patrice Brousseau (Aug 12, 2020)

jb welder said:


> Are you using the footswitch or not? If not, is it a switching jack and is the switch contact good?


It wasn’t the problem, I was the problem 

Grid wires were reversed! I took the opportunity to replace 5 or 6 100k’s, one 1meg, two .022 and one .01. All around V3 and V4 (tremolo and reverb).

I also swapped the JJ E34L’s from my newly acquired YBA-3 Custom Special and re biased accordingly.

The tremolo is a bit different from the old one but it looks to be stable... Will test it tomorrow.


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## Patrice Brousseau (Aug 12, 2020)

Paul Running said:


> If you suspect the start cct., you could momentarily ground the grid of the osc. (the pink-dot in the diagram below):
> View attachment 362404


Operator error: grid wires reversed!!


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## Patrice Brousseau (Aug 12, 2020)

Quick question:

I would like the trem to be deeper and slower?


I know that changing one (or two) of the .01 to .02 will slow it.
Now, not sure it applies to the opto trem: reducing second cathode resistor from 100k to 56k?

**The Traynor tremolo, when it worked was deeper, almost choppy and I liked it!

Thanks,

Patrice


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## Paul Running (Apr 12, 2020)

Here's a reliable tremolo...no pumping, kicking or ticking:


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## Patrice Brousseau (Aug 12, 2020)

Paul Running said:


> Here's a reliable tremolo...no pumping, kicking or ticking:
> 
> View attachment 362510


Interesting! Could work with my YGL3? How would it connect to the actual circuit? I guess blue dot is input? Where do the plates should connect? Not that I will install it but for future reference in case I'm tired of the opto circuit.

Anyway, another swap of 12AX7 (an old noisy but strong USA) and some high pitched oscillation noise (always present when master was cranked) is gone. There was a Sovtek there...

As a sidenote, my Gretsch shortscale bass was breaking up really soon in channel one and I couldn't figure why. The culprit: the JJ ECC83 I've put there in place of the original noisy EHX. Now, with an Electrohome (Rogers), no more breakup... It shows how important it is to have good tubes in the right spots.
Thanks,

Patrice


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## Paul Running (Apr 12, 2020)

Patrice Brousseau said:


> It shows how important it is to have good tubes in the right spots.


I allow for ±20% tolerance for tubes. Yeah, the blue dot is the oscillator output. As you are aware there are several methods to modulate the main signal; the isolation method offers good performance. I would provide a high plate supply to the plates of the osc. tube...300VDC.


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## Patrice Brousseau (Aug 12, 2020)

Update: running fine at school since two weeks doing keyboard, guitar and bass duties. Perfect for the job…

The tremolo, albeit different from the original, is stable and always work!


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