Strange new vibrato circuit in DR Reissue

[Pedro Vecino]

Hello. I have discovered in a Deluxe reverb reissue (bought today) a strange and complex circuit that replaces (it is what seems) to the cell neon/ldr.
The basic vibrato circuit in the board seems to be identical (already I will confirm it) and all this matter is to only replace the cell neon/ldr.
The system works worse than the traditional one, generating in addition background noise non-existent previously.
Can someone explain the motive of this or contribute something of light?
Strange thing...

[Bruce / Mission Amps]

Hello. I have discovered in a Deluxe reverb reissue (bought today) a strange and complex circuit that replaces (it is what seems) to the cell neon/ldr.
The basic vibrato circuit in the board seems to be identical (already I will confirm it) and all this matter is to only replace the cell neon/ldr.
The system works worse than the traditional one, generating in addition background noise non-existent previously.
Can someone explain the motive of this or contribute something of light?
Strange thing...

Wow... guess it's been a long time since I've worked on a reissue DR... I don't remember that circuit board at all.

[Pedro Vecino]

Hello. Finally, after having verified entirely the vibrato circuit, the new circuit only replaces the cell neon/ldr.
From the mains transformer AC line for bias and vibrato goes directly to the new PCB and from there it comes back to the general PCB (two original red cables in reissue model).
I have removed the new circuit and installed a classic optocoupler and the circuit works like always and without noises.
All that does not make sense and it is possible that it has relation with the ROHS norm. The most possible thing is that all Fender amps with this type of vibrato are made now with this system.

Another innovation that has this new Deluxe reverb is the incorporation extra of resistors in the 12Ax7 grids (apart from the typical ones of 68K in the inputs)

That´s all.
Best regards

[Chuck H]

Jeez.. What is going through the "engineers" minds. The reissue Fenders keep drifting further and further from the original circuit. And the more of that crap you remove, the better they sound and the more reliable they work. Same thing with the middle era Boogie amps. Why do mass MFG companies hire these big school, high math, pocket protector engineer types that overdesign and confound the circuits so badly that you end up with something that is ultimately less reliable with dry bad tone???

You know the original opto circuit costs less than that board and sounds better. And yet...

IMHO guitar amps have always been, and always will be, a "less is more" effort. Anyone else ever notice that half of the mods for modern amps involve removal of bleeder circuits, local NFB loops and solid state junk?

These MFGs should be recruiting guys like Bruce and Enzo to bounce designs off of. I'm certain that just by acting on a consulting basis they could resurrect Fenders tone legacy.

Chuck is ranting again. Please excuse the beer.

[johnwilliamhunter]

Weird, is that a new stock Deluxe Reverb Reissue? Mine, from 2006, doesn't have those extra boards.

[Enzo]

I don't suppose anyone bothered to contact Fender to ask about this instead of guessing?

[Pedro Vecino]

Deluxe reverb and Twin reverb al least bring this circuit in Europe. Already I have four (two of every). The most ancient will have about one year or less. The most new, one week.
Regards

[Enzo]

Just a guess: The photocell used in the Fender opto bug is cadmium sulfide, and they needed to get rid of the CdS for RoHS.

[ribo1989]

Strange new vibrato circuit in DR Reissue

Hello. Finally, after having verified entirely the vibrato circuit, the new circuit only replaces the cell neon/ldr.
From the mains transformer AC line for bias and vibrato goes directly to the new PCB and from there it comes back to the general PCB (two original red cables in reissue model).
I have removed the new circuit and installed a classic optocoupler and the circuit works like always and without noises.
All that does not make sense and it is possible that it has relation with the ROHS norm. The most possible thing is that all Fender amps with this type of vibrato are made now with this system.

Another innovation that has this new Deluxe reverb is the incorporation extra of resistors in the 12Ax7 grids (apart from the typical ones of 68K in the inputs)

That´s all.
Best regards

Hello Pedro,

Last week I bought a DRRI, European version with a digital vibrato circuit in it. After reading your post, I decided to challenge my poor soldering skills and replace the digital circuit wit a proper opto coupler. So far I managed to remove the digital circuit completely without any problems. But, as to the extra resistors added by Fender to eliminate the digital noise, I am not sure which ones should be removed. When I look inside, I see resistors soldered directly to:

V1 pin 2 and 7
V2 pin 2 and 7
V3 pin 7
V4 pin 2 and 7

Are these resistors the extra ones you mentioned? Are there any other components to be removed or replaced so that the traditional vibrato works properly?

Any guidance would be highly appreciated.

Many thanks in advance,
Ad

[nickb]

Just a guess: The photocell used in the Fender opto bug is cadmium sulfide, and they needed to get rid of the CdS for RoHS.

I do believe you are correct.

Strangely however, OK it's to use Cadmium on solar panels in the EU. I'm sure the weight of cadmium in solar panels far, far exceeds that in photocells.

But I must stop, else there will be more ranting and spilling of beer.

[Pedro Vecino]

Yes These grid resistors (I think they were 10K 1/4 watt) are not necessary.
Regards

[ribo1989]

Yes These grid resistors (I think they were 10K 1/4 watt) are not necessary.
Regards

Thanks!

[ribo1989]

Yes These grid resistors (I think they were 10K 1/4 watt) are not necessary.
Regards

I removed the extra grid resistors and soldered the green grid wires directly to the pins 2 and 7. The opto coupler arrived today. I soldered it to its place. I switched on the amp. No noise or buzzing whatsoever. A barely audible ticking noise from opto coupler was eliminated completely by pushing the green grid wire of V5 pin 2 away from the other wires of V5. The amp sounds much better than before.

But the tremolo is very shallow now. The tremolo Intensity pot does nothing until 9. When I set the Intensity pot to 10, I have a very very shallow tremolo.

Any ideas what the reason might be?

Any guidance would be highly appreciated.

[Pedro Vecino]

I have noticed that not all neon / LDR cells are equally effective. Some offer less intensity than others. Depending on which model you have purchased may have a relationship with that. In any case it is advisable to review the voltages around the circuit and the good operation of the tube.
Regards

[Alex/Tubewonder]

Yes, this circuit is due to ROHS and CdS being on the banned list since July 1st 2007. Solar power cells don't use CdS, way too low efficiency besides ROHS.
That circuit is a way over the hill attempt to emulate dynamics of the neon lamp/CdS photoresistor based tremolo. There are much simpler ways of getting there.
LED/PhotoFET chip can be used for this job, a much simpler, smaller and cheaper circuit to control the dynamics will suffice.
Fender would be welcome to stuff my pockets in exchange for a license to use my circuit