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Question about Opto (from New Sensor)

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12/12/1999 1:25 PM
FuzzFace	Question about Opto (from New Sensor) I bought Opto for my DR project tremolo section. But there's no info... It just wraped with black tube. and 4 lead... Which lead are In? Out? etc? help..

12/12/1999 2:44 PM
Benjamin Fargen	Fuzz, You need to look inside to see which side is the LDR wires and which is the neon bulb wires.......then look at a layout from any larger blackface Fender Amp to see the correct placement in the circuit. Let me know if you need the layout picture. Benjamin

12/14/1999 6:36 PM
Doc	Measure the resistance between the pairs of wires at each end. The end with the neon bulb will have no continuity whatsoever, open circuit to low voltage DC. The photoresistor end will have a high resistance, up in the megohms.

12/17/1999 1:31 AM

I had the same problem with the New Sensor optoisolators. The shrink tubing is much tighter than the original Fender components, so you can't just look inside and tell where the leads go. Unfortunately, the photoresistor side measures over 20M, so this trick didn't work with my meter. I wound up putting the leads in series with a voltmeter and measuring a high voltage. The photoresistor side will allow some voltage to get through to a digital voltmeter, but the neon bulb side won't.

When I installed it, I left the leads uncut in case I had made a mistake. It only takes a couple of minutes to solder in place anyway, so you stand a 50-50 chance by just guessing. After I verified that the installation was correct, I went back and trimmed the leads.

The method worked, but there is a dot marking one side of the New Sensor optoisolator. Unfortunately, I didn't write down if the dot means bulb or photoresistor !

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