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Vintage threads from the first ten years

Mutron III photocell substitute

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10/30/2000 5:03 PM
Anders	Mutron III photocell substitute What's the best Mutron III photocell substitute today? I understand that the new E-H Q-tron is pretty much a Mutron III clone, anyone knows what they're using in them?

10/30/2000 6:20 PM
Carl S.	I recently purchased this part from CJLectronics for $12.00 US. It's supposed to be identical to what was in the original Mutron. He can be contacted at: cjlectronics@yahoo.com

11/1/2000 12:07 PM
Anders	I bought one from CJ some time ago but it doesn't do the job well. At 4mA LED current it goes down to 2kOhms while the original cell stopped at 25kOhms.

11/2/2000 1:29 PM
CJ Landry	Are you sure about that Anders?? I get 2K ohms at 20mA on almost all of them. CJ

10/30/2000 10:42 PM
MikeB	The Qtron has a small black tube, with no markings (at least the one I opened up) with 6 legs, 2 for the LED and 4 for the LDR(s). With a normal red LED, and two LDRs that have a fast response, have minimum resistance of about 10k and max from 500k to a meg, you'll get pretty close. I doubt there is anything too special about the bits in the "black tube", it is just nicely packaged. MikeB

10/31/2000 10:02 AM

10k-500k/1M is close to the original?
I've used 100k-4M (or something) and that worked fine. On the other hand, there's a lot more filter caps in mine to tailor the response, that might account for it.
LED and LDR's is indeed just what is in that "magical" canister. As long as you use a closed box, you don't even need to cover the LED/LDR combo, just seat the LDR's side-by-side, bend the LED-legs so it's facing the LDR's spot on, and you're there.

11/1/2000 12:40 AM
MikeB	> 10k-500k/1M is close to the original? I wouldn't know about that. There is likely a large component variation that can be tolerated or adjusted away using the available controls. What cap mods have you done to tailor the response? One that comes to mind is subbing in a .1uF cap for the 2.2uF cap leading to the envelope detector - reduces the sensitivity to bass frequencies somewhat. MikeB

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