fender deluxe reverb 65 repair

[tepsamps]

Hello,
i'm trying to repair an old deluxe reverb. I changed the big capacitors first because it has not started for 20 years.
The first channel is working good.
The second one, without reverb tube and tremolo tube works fine also.
I did not put the reverb tube yet but i tried the tremolo. When I switch it on, I see the optocoupler blink (red light). But it makes a ticking noise and it does not work as i did not hear a swing in the volume.
When dark, the resistor is about 450 kohm and i read it should be 2M.
But actualy, i don't really anderstand the tremolo circuit. I see the half sine wave to the grid, of the first triode, so i see the LFO, but i don't see where the audio signal is modified.
For the reverb, there is an input and an output wire, bot for the tremolo i see only one wire going from the intensity pot wiper to the phase inverster, between the 100 nF cap and the 220 k resistor.

Can someone explain me so i can debug?

Thanks

PS : putting a tube for the tremolo adds a lot of noise in the channel 2 even without engaging the tremolo switch... No ticking noise but noise like humm or interferences...

[g1]

Do you mean the 65 DR re-issue? Schematic attached.

[tepsamps]

No, the old one with paper filter capacitors...

Actually, meanwhile, i anderstood the circuit. So it provides a variable resistor (shunt) to ground. But how is it possible it does not affect the first channel?

So, my optoisolator must be dead...

Other thing: there are 2 shields made by a thin wire wrapped around a thread of other wires. One for signal wires, one for power supply wires. And the shield is connected to ground at each side. When i use a shielded wire for signal, i put the shield to ground at only one side. If not, i create an ground loop i've been told. You see what i mean?

[Helmholtz]

Actually, meanwhile, i anderstood the circuit. So it provides a variable resistor (shunt) to ground. But how is it possible it does not affect the first channel?

The tremolo works by varying the plate load of V4B.
Max. tremolo load resistance is limited by the value of the intensity pot (50k). Exact dark resistance of the LDR doesn't matter as long as it's much larger than 50k.
The 220k mixing resistor isolates the normal channel from the tremolo.

[tepsamps]

The tremolo works by varying the plate load of V4B.
Max. tremolo load resistance is limited by the value of the intensity pot (50k). Exact dark resistance of the LDR doesn't matter as long as it's much larger than 50k.
The 220k mixing resistor isolates the normal channel from the tremolo.

That's what i thought reading articles on tremolos, the bias shifting? But i saw it differently today...
And i still don't anderstand. What kind of bulb is it? Why a 100k cathode resistor?

If the bulb is on, the photoresistor is almost 0 and the signals goes to ground via the intensity pot... It's wrong?

[Helmholtz]

That's what i thought reading articles on tremolos, the bias shifting? But i saw it differently today...
And i still don't anderstand. What kind of bulb is it? Why a 100k cathode resistor?

If the bulb is on, the photoresistor is almost 0 and the signals goes to ground via the intensity pot... It's wrong?

It's a neon gas discharge bulb. When it's on, photoresistor (LDR) resistance should be low.

Bias shift tremolo is different. It directly connects the tremolo signal voltage to the power tube grids (no optocoupler).

[tepsamps]

Thank you Helmholtz for giving me answers.
I saw a topic on this forum about de fender tremolo, with 2 videos, very instructive.
But no explanation about this wire coming from the bias supply. An half sinusoide to the input of the oscillator via a 2M2 resistor.

I don't find a 3M RA pot, so is it possible to change it for a 1M RA pot if i change the first 0.02 uF by a 0.068 uF?

Maybe the ticking noise commes from this 3 caps in the oscillator?

I ordered a replacement for the optocoupler...

[Helmholtz]

As your oscillator works (neon flashing) there's no reason to replace oscillator parts.
The ticking is not caused by the oscillator but rather from lead dress or a bad optocoupler.

[Chuck H]

Thank you Helmholtz for giving me answers.
I saw a topic on this forum about de fender tremolo, with 2 videos, very instructive.
But no explanation about this wire coming from the bias supply. An half sinusoide to the input of the oscillator via a 2M2 resistor.

I don't find a 3M RA pot, so is it possible to change it for a 1M RA pot if i change the first 0.02 uF by a 0.068 uF?

Maybe the ticking noise commes from this 3 caps in the oscillator?

I ordered a replacement for the optocoupler...

https://www.allparts.uk.com/products..._JXSzhD3A2qmGh

[tepsamps]

https://www.allparts.uk.com/products..._JXSzhD3A2qmGh

Thanks, I did not check CTS as they are very expensive, only Alpha. But i found one CTS 3MRA for less than 4 € in Germany...

[Tom Phillips]

...Maybe the ticking noise commes from this 3 caps in the oscillator? I ordered a replacement for the optocoupler...

If your amp still makes the ticking sound when you get the tremolo working with the new optocoupler, then you can implement the changes described in the attached Fender Service bulletin.
Fender Service Bulletin - Tremolo Ticking Fix.pdf

[tepsamps]

If your amp still makes the ticking sound when you get the tremolo working with the new optocoupler, then you can implement the changes described in the attached Fender Service bulletin.
[ATTACH]n1004992[/ATTACH]

Ok, thank you all. I put the new optocoupler, and changed the lead dress. I put a brand new tube and I still have a light oscillating noise, but when i play, i don't hear it. And it works, the tremolo effects is effective and it's a cool effect.
Thanks for your inputs

[tepsamps]

Far better with the cap on the 10M resistor.

I have another problem now. So i put back the chassis into the combo shell, and the tone was crappy when rising just a little bit the volume, and i saw sparkles inside the rectifier tube GZ34.
I switched it off, and put the old GZ34 that was still working and no sparkle anymore, but the tone is bad. And i noticed that the rectifier socket was loose at first.

So i wonder if i should remove the GZ34 for a diode rectifier... Anyway i don't anderstand what is happening now....

[Chuck H]

Please check for bias voltage at pin 5 on both 6V6 sockets. If you have have about -35V to -40V then please interpret "crappy" and "bad" more clearly. And report on other things like plate voltages and whether all the controls are working.

[Tom Phillips]

... I noticed that the rectifier socket was loose at first....

Octal tube sockets are designed with the individual female contacts floating within the body of the socket assembly. Therefore, it is normal for the tube to feel loose. This design feature is purposely done to allow each pin socket to align with the male tube pins while preventing excessive side stress to the tube base.

...So i wonder if i should remove the GZ34 for a diode rectifier...

That's not a great solution because it will raise the high voltage and will also change the character of the amp. It appears that you got a bad new rectifier. Unfortunately, this is fault does happen with modern tubes.