# Weird tremolo issue on my ‘69 bandmaster reverb



## warplanegrey (Jan 3, 2007)

Howdy. 

Here's the issue: My tremolo doesn't seem to be getting any guitar signal. I can hear the background noise change with me increasing and decreasing the intensity and speed pots, but my guitar signal is unaffected.

Here's what I've tried:

Replacing the tremolo driver tube (with a handful of tubes to ensure it's not that)
Changed out all of the old white Mallory caps with new Spragues
Inspected the roach/photocell (it lights up and changes with the pots)
Touched up and reflowed the solder on the entire tremolo section

Is anyone able to offer insight as to what might be the issue? 

Thanks!


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## Alan Small (Dec 30, 2019)

the trem signal flows out of the 7025 previous tube to the trem driver tube....try cleaning socket(s) and different tube in that position; cleaning and retensioning all the sockets is a good annual habit.


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## Latole (Aug 11, 2020)

Issu may come from photocell and /or all tremolo caps 2 X ,01 and .02
Or from bad contact on RCA footswich jack


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## Paul Running (Apr 12, 2020)

warplanegrey said:


> Inspected the roach/photocell (it lights up and changes with the pots)


That means the oscillator is working. Can you follow a schematic?


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## nonreverb (Sep 19, 2006)

The LDR (photocell) is a path to ground for the guitar signal. If you hear the pulse but there is no effect, the only possibility can be the LDR is bad. You should be able to hear a little bit of pulse when the level is turned on full while playing.


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## Latole (Aug 11, 2020)

You have 2 choice 
1-Take many hour to try find wich parts is bad with no garantee success or
2- Replace right now caps and cell

I fix many tremolo issues and ai build my own photo cell for $3


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## warplanegrey (Jan 3, 2007)

Alan Small said:


> the trem signal flows out of the 7025 previous tube to the trem driver tube....try cleaning socket(s) and different tube in that position; cleaning and retensioning all the sockets is a good annual habit.
> View attachment 403931


I should have mentioned that I have also cleaned all of my tube sockets (I usually do this every year or so).



Latole said:


> Issu may come from photocell and /or all tremolo caps 2 X ,01 and .02
> Or from bad contact on RCA footswich jack
> 
> View attachment 403938


Yeah, I'm thinking the photocell may be pooched at this point. I'm going to track continuity from the wiper of the intensity pot to the roach, and from the intensity pot end to the 3M3 resistor that is connected to the pin 7 grid of V4.



Paul Running said:


> That means the oscillator is working. Can you follow a schematic?


Yes I can!



nonreverb said:


> The LDR (photocell) is a path to ground for the guitar signal. If you hear the pulse but there is no effect, the only possibility can be the LDR is bad. You should be able to hear a little bit of pulse when the level is turned on full while playing.


Yeah, I'm starting to get that feeling.



Latole said:


> You have 2 choice
> 1-Take many hour to try find wich parts is bad with no garantee success or
> 2- Replace right now caps and cell
> 
> I fix many tremolo issues and ai build my own photo cell for $3


You make a good point. I've spent countless hours trying to address why the reverb wasn't working just to find out that it was the reverb pan that had died. Facepalm.

Better to just replace the likely suspects and get it out of the way.


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## Latole (Aug 11, 2020)

Photo cell: Neon liggt may work , not photo resistor


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## Paul Running (Apr 12, 2020)

Have you tested the receiving side of the LDR? If it is an original part the resistance will vary with light intensity, if it is a photo-cell type.


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## Paul Running (Apr 12, 2020)

Should you become interested in experimenting with opto-isolators you can build your own with incandescent or LED for the transmitter and photo cell for the receiver. Various alterations in intensity, light dampening and photo cell linearity will affect the dynamics of the tremolo.
Here's the DIY I experiment with: chunk of black PVC pipe, LED bulb and a photo cell from an oil burner.


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## loudtubeamps (Feb 2, 2012)

If you have verified that the pre amp tubes are ok...I would suggest hitting all of the solder points related to the trem circuit, especially the ceramic disc capacitors adjacent to the photo cell and the leads on the roach itself.


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## Hammerhands (Dec 19, 2016)

It only affects the Vibrato channel.


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## warplanegrey (Jan 3, 2007)

Hammerhands said:


> It only affects the Vibrato channel.


Yep, that's the one I'm plugged into.


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