| J 596 RV Tremolo Coupler? [message #29550] |
Mon, 12 May 2025 22:32  |
schmittp
Messages: 4
Registered: May 2025
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Junior Member |
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New to this forum, not new to fixing Vintage Kustoms. I've been fixing pro audio for > 50 years. I have a 1967 year J 695 RV that works, all except for the tremolo. I have found the circuit is identical to the K200 units, but I can't find any information on the optical coupler. I know it was an incandescent lamp and photocell combination. I fiddled around some, and got a lamp in it that worked a little, little being little tremolo effect. Speed and intensity seem to work OK. The photocell's resistance doesn't go down very far, I suspect it is in bad shape. The lamp was missing when I got the amp, so I don't even know what it looked like. The schematic I have isn't very good resolution, and makes no mention of specifications for the coupler unit.
If anyone could share any information about the circuit's operation, the coupler specifications, or how to replace the coupler with a Vactrol, that would be very appreciated.
The amp also had terrible hiss, that varied with the volume controls, but turning them both down all the way didn't kill all the hiss. With both volume controls at zero, the treble controls still changed the amount of hiss. I fixed the hiss by replacing all the transistors and carbon resistors in the preamp. The hiss isn't caused by one part, it seemed to be all of them. The amp is very quiet with no signal now!
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| Re: J 596 RV Tremolo Coupler? [message #29556 is a reply to message #29550] |
Thu, 15 May 2025 13:13  |
chicagobill
Messages: 2022
Registered: April 2003
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Senior Member |
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I've fixed a few of the vibrato circuits in the past. The original lamp is #48 lamp and the original photocell is a Clairex CL-603.
That being said, I have used a 10 volt incandescent lamp as a replacement and I don't see why an LED wouldn't work in there as well. You would have to adjust a resistor or two to get the voltages correct, but that shouldn't be too hard to do.
As for cds cells, they are getting harder to find now. I used to get assortment packs from Marlon Jones, but they have recently closed down. You need to find a cell that responds quickly so that the vibrato effect is deep and has a value that will give a good effect.
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| Re: J 596 RV Tremolo Coupler? [message #29559 is a reply to message #29557] |
Thu, 15 May 2025 21:33 |
schmittp
Messages: 4
Registered: May 2025
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Junior Member |
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It works! I have a lot of NOS and used parts; I actually have #48 lamps, and digging into my collection of photocells, I also have a few NOS Clairex CL603AL
Which is 33 Megs dark, and 3.5K lighted. (You can download a free datasheet from the 'Net, just Google it.) The best one I had wasn't perfect, It was more like 5K ohms lighted. I soldered some short wires onto the lamp, put them nose to nose and heat-shrinked them together.
The tremolo works, if not as 'deep' as one might like. YAY! Thanks again to Vintage Kustom and chicagobill.
An old Kustom lives again to soldier on into the future. Really nice amp, anybody want to buy it?
Advice for others: The Clairex CL603 was available in three versions; CL603 which is 133K ohms lighted; The CL603A, which is 75K lighted, and CL603AL, which is 3.5K lighted. I used the CL603AL. I'd say the lower the lighted resistance, the 'deeper' the tremolo.
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| Re: J 596 RV Tremolo Coupler? [message #29561 is a reply to message #29550] |
Fri, 16 May 2025 13:43 |
chicagobill
Messages: 2022
Registered: April 2003
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Senior Member |
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Great to hear that you got it working!
Technically, the effect is vibrato (pitch shift) not tremolo (volume shift), thus the RV (reverb/vibrato) designation. Effect depth is controlled by two factors, the cds cell resistance and by the lamp brightness which go hand in hand. You can try adjusting the lamp brightness by changing the lamp driver circuit resistor R326. Don't go too far or you risk burning out the lamp.
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