Mutron Flanger - oscillating without input  [SOLVED]

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TornadoHair
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Post by TornadoHair »

Mutron Flanger. I’ve had this bad boy for awhile, but I don’t believe it’s ever sounded the way it really should since I’ve owned it. Very grainy/distorted sounding, self-oscillating, and a lower frequency siren effect, even without signal. All knobs do function. [I just recently did a full recap (14 electrolytics) on my ‘81 DOD Flanger 670, which was malfunctioning into full-on siren effect. After the recap, it works perfectly and sounds absolutely lovely.] I was planning on doing a full recap on the Mutron, but I didn’t know if anyone had info or instructions on a calibration. There are 5 internal trimpots, which I did mess around with (but not before measuring all trimpot voltages and resistances first), but that didn’t seem to clear up my issues. Anyone ever work on one of these, and could shed some insight or tips? I’m dying to get it going! Much thanks!
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jreeves47
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Post by jreeves47 »

did you try http://www.lsound.com ? That's who Mike Beigel will send you to. I know because I sent them my mutron flanger and they did it perfect. Good luck

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modman
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Post by modman »

viewtopic.php?f=10&t=12968 - how to calibrate Mutron Flanger
viewtopic.php?p=145224#p145224 - schematic
TornadoHair wrote: 20 May 2020, 17:34 I’m dying to get it going! Much thanks!
Take the lid of, check the pedal for visual damage and check whether the transformer is delivering the proper voltage...
jreeves47 wrote: 21 May 2020, 13:15 did you try http://www.lsound.com ? That's who Mike Beigel will send you to. I know because I sent them my mutron flanger and they did it perfect. Good luck
Does he have a stash of SAD1024s? If it's 'calibration' it's just setting the trimpots... I wonder who much he charges for that. I'm not saying it's easy, but for the price of sending a pedal out for repair you could buy a nice second hand scope.
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jreeves47
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Post by jreeves47 »

modman wrote: 21 May 2020, 19:03 viewtopic.php?f=10&t=12968 - how to calibrate Mutron Flanger
viewtopic.php?p=145224#p145224 - schematic
TornadoHair wrote: 20 May 2020, 17:34 I’m dying to get it going! Much thanks!
Take the lid of, check the pedal for visual damage and check whether the transformer is delivering the proper voltage...
jreeves47 wrote: 21 May 2020, 13:15 did you try http://www.lsound.com ? That's who Mike Beigel will send you to. I know because I sent them my mutron flanger and they did it perfect. Good luck
Does he have a stash of SAD1024s? If it's 'calibration' it's just setting the trimpots... I wonder who much he charges for that. I'm not saying it's easy, but for the price of sending a pedal out for repair you could buy a nice second hand scope.
I don't remember mine needing any chips replaced. Of course I sold it once it was working properly

TornadoHair
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Post by TornadoHair »

Well I went ahead with the recap and I’m super happy to report that it’s now working beautifully and sounding killer! Literally 90% of the caps I replaced tested way off on capacitance and/or super high ESR. I definitely took my time, about 8 hours, but that included measuring every cap in-circuit, and then again out-of-circuit after they were pulled. It’s quite the process removing the guts, then reinstalling. I got scared for a minute when I tried to test it before reassembly and got nothing but a loud hum, but that went away after it was remounted into the enclosure. Probably a grounding thing. Thanks to everyone who replied!

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modman
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Post by modman »

Good to hear it's working again... replacing all electrolytics is quite a job...
thanks for reporting back this will surely help other in the future... I don't want to impose... but there are really few demo clips of this pedal available.
I wish I could save that demo clip of the self oscillating pedal before repair.
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