Sunn Sentura Tremolo Fix - Dead CDS cell

[Drewline]

I've been trying to resurect a Sunn Sentura I. The amp is a real science project. While it has a rectifier tube & socket the power transformer is missing the 2 yellow leads to supply 5 VDC to the rectifier. I fabricated a solid state rectifier tube which works fine plugged into the original socket. After cleaning up the wiring & the soldering everything worked except the solid state tremolo. The oscillator was working powering the original lamp. No volume change. The CDS cell in Sunn's version of the Fender bug was dead. As I have said in previous posts, I spent many years working as camera repairman. I got some surplus cells from junk cameras from a friend & found that they were the wrong sensitivity for this circuit. The internet lead me to Allied Electronics who actually sells CDS cells made by Silonex. I spent considerable time with the spec sheets finding a suitable replacement cell. It is: Silonex NSL-5160 The cell fits inside the original housing, the tremolo is now strong. I did replace the 6 electrolytics in the circuit after I confirmed the bad cell.
The cell is the black object in the photo. I used Pliobond covered with black paint to glue the cell back into the housing & to secure it to the PCB as it originally was.
Here is a photo of the Reverb / Tremolo PCB used in this amp.



I hope this helps!

[loudthud]

Any idea what light bulb was used?

[Drewline]

It worked & was glued in real well so I left well enough alone. Looks like a grain of wheat type bulb probably 6V. The schematics call for 4.5Vdc across the bulb.

[patlaw]

There is some really useful information in this thread. I wish there were some better pictures. How did you get the old cell out?

Marked for future reference. Thanks.

[Drewline]

The cell was glued into the the housing. I gently seperated it after unsoldering both ends from the board. I used black nail polish to glue the new cell in.

[patlaw]

Did you save the old one, by any chance? I'm curious as to whether it was a "loose" cell or whether it was in a can, like the replacement you used.

[Drewline]

The cell was in a housing same as the replacement. I return parts changed to the customer always. I see no reason to save dead parts.