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Vintage threads from the first ten years

What Optocoupler in Deluxe Reverb?

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6/1/1999 7:49 PM
LSC	What Optocoupler in Deluxe Reverb? Please Let me know Spec of Opto that needs in my DR Project. I know Hoffman amp sells them. but I live in Korea and I have a plan to order to mouser. so If you can tell me mouser stock no. it will big help to me. have a nice day bye

6/2/1999 2:23 PM

Mouser probably doesn't have these. They were a custom engineered part back when the amp was new. Someone is currently making almost-exact replacements for the limited market of guitar amps. You'll probably just have to order it from a place like Hoffman, that deals specifically in guitar amp electronics.

I tried to make my own replacement out of a cadmium sulfide photocell and an NE-2 neon bulb, secured in a black heat shrink tube. Seems simple enough, right? The neon bulb was a known quantity, but the photocell was a different story. I tried various pieces available from Mouser, picking devices that had light & dark resistance values close to what the original cell had (what I tried to measure). The one with the best match still worked poorly. Without knowing the spec's of the original cell, the light resistance, dark resistance, and light/time response, you'd be extemely lucky to come up with a decent home made plug-in replacement.

I bought a replacement lamp/cell assembly a few years back from magic parts, described as an exact replacement, which works very poorly in my SF twin reverb. It responds too rapidly, and instead of giving a nice smooth modulation effect up & down, it just seems to sharply turn on & off. Hopefully the recent ones from Hoffman are closer to the original.

This part will seem to cost more than you think it should, but there's really no way around it I know of.

Notice that the heat shrink tube covers the photocell and is longer than the bulb, but the ends are not closed? A neon lamp (except for a particular type) needs a minute quantity of ambient light (a few photons) to fire. I find that point interesting.

6/2/1999 6:34 PM

There are many places that have these, and they don't cost much. If I can remember.Smart Parts,Fender, New Sensor,Torres, and a few others have them.Last ones I bought cost about 5 dollars. I put in one post about some of these moduals being bad. it talks about them in my Fender service manuel.It says that the photo cell is what is defective,will give weak or reduction in output when the intensity is turned up.The replacement fender part number was 030874.. and it says its a NE2 neon lamp, and a photo cell[thats all it says].025 piece of heat shrink tubing.It said it goes bad and has inadequate coating on the surface of the unit, it will look dull rather than shiny. [Richie

6/2/1999 6:37 PM
Tony R.	I recently got one from Charles at SwampAmp. www.swampamp.com Tony

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