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Vintage threads from the first ten years

Re: MuTron III schematic?

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2/3/1997 5:11 PM
Craig	Re: MuTron III schematic? Thanks, I'd love to get a look at your schematic. As I say, I didn't notice the component you describe, either in the one I am working from, or the one in the music store. Interesting...

2/4/1997 9:49 AM

Hmm. I'm starting to get the sense that both Craig and Steve are correct, but
both are working from different revisions of the design.

If you look at some of the early Electro-Harmonix boxes from the same time
period, it was not at all unusual to have a completely different design, yet
market the device under the same name. I guess Mike Matthews didn't know
his stuff was vintage yet!

Chances are one model did use optoisolators, and another used OTA's. If
memory serves, the Mutron was a kind of dirty-sounding box, with a pleasing
grit to it. Sounds like an OTA to me, but I could be wrong.

Incidentally, many boxes of the same era used CA3094's instead of CA3080's.
I couldn't tell you how to identify them through pin connections, but if you
check the schematic for the EH Small Stone at Jack Orman's site, that should
tell you.

2/4/1997 12:39 PM

That's an interesting possibility, Mark; and it occurred to me as well when craig said he couldn't see anything that looked like the opto-unit. I know there were at least two different versions: The early ones had a compartment in the bottom that took two 9-volt batteries, and it was usually sold with the optional external power supply box because the batteries didn't last very long. Later ones had a built in power supply (I think it even had a three-prong ac cord) and no battery compartment. I've never seen the insides of one of these so who knows? Maybe they changed more than the power supply. How about it, Craig? Does the one you're looking at have an ac power cord attached?

2/6/1997 11:00 AM
Craig	The one I have has the 2 - 9v's and external bi-polar power supply.

3/5/1997 12:10 PM
CJ Landry	Hope you don't mind me jumping in on this conversation, but I just finished repairing a Mutron III and it was the type with an opto- isolator. The problem was the PS-1A external power supply had a blown 9.1v Zener. I replaced both and it worked great. Anyway, it also had 2 - 9v battery holders in it. Hope this helps

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