Ampeg Tremolo Module "TM1"

[KingCameron]

Guys,
I have a GS-12R built similar to the attached schematic. (vintage)

This amp has a tremolo module called "TM1". This module appears to be some kind of LDR, or photoresistor set-up.

Can someone tell me how to test it?
Can I replace it with the Fender LDR? Other versions? (if needed)

Any other info on this little gizmo would be great

[Bruce / Mission Amps]

Originally Posted by KingCameron

Guys,
I have a GS-12R built similar to the attached schematic. (vintage)

This amp has a tremolo module called "TM1". This module appears to be some kind of LDR, or photoresistor set-up.

Can someone tell me how to test it?
Can I replace it with the Fender LDR? Other versions? (if needed)

Any other info on this little gizmo would be great

Yes it is an LDR but quite a bit different in values then the Fender type. They are not interchangeable.
I'm actually working with another person to see if we can duplicate these things but at a more reasonable price... depending on which kind you have, you can buy something like it from Flip Tops.
http://www.fliptops.net/catalog/index.php?cPath=25_56
Regardless, it's hard to test that damn thing because it is a closed up device and the resistance is really really REALLY high... like 30M to 40M and the turn on (high to low resistance) "slew rate" is wacky.
Not just any cell will even come close to working.
But you can "kind of" check one part of it if you make sure all the light is blocked and then read the resistance across the two cell leads.
Since most bench ohm meters can't read as high as the cell is... it should read like an open circuit, but if you have a decent meter and put a "KNOWN" (and I mean measure it first) 10m resistor in parallel with it, you should see that the two in parallel is much less then 10M.... etc.
The blinky light thing is a little hard to tell if it is working.
For the casual repair... after checking the other parts of the circuit, I'd just assume it is the cell and replace it with what is available.

[KingCameron]

Bruce,
As always, thank you very much for your responce. You're awesome!

Please let me know if you ever come up with a replacement for TM1. I would be very ineterested to get one. I am not sure the one I have is bad, yet. But, if there was a reasonably priced replacement, I'd probably swap it out anyway.

I will also look at the web-page you recomended.

Thanks,
Cameron

[KingCameron]

Bruce,
I looked at Fliptop's version of the TM-1. It does not look the same, and is $35, but may be electrically functional.

I think I'll get the rest of the amp dialed in first, and make sure the tremolo LDR is the issue, before drop the dough on this one...

although it is nice to know there is a back-up available

[KingCameron]

Here is a picture of the Tremolo Module in the Ampeg GS-12R

I'd like to get a new one of these.

[Bruce / Mission Amps]

Originally Posted by KingCameron

Here is a picture of the Tremolo Module in the Ampeg GS-12R

I'd like to get a new one of these.

Yeah those are stinkers.
Possibly their VM-1R model will work in your amp.
Call them and see what they say.

By the way... if you can replace all the those blue e-caps (could be Ducati) on your circuit board.

[KingCameron]

Yup. They're Ducati caps...why should I change them? (Other than the obvious) Are they known to be bad?

Thanks for the tips..

[darrellcheng]

Age will dry out e-lytics. The old ones probably stay in value for 10-20 years max. new ones will last 30+. You can measure capacitance to see if they've drifted.