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Old 06-07-2021, 02:33 PM   #1
Camarada78
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Default MXR Carbon Copy High Pitched Noise

Hello,

I have a MXR Guitar Pedal here that turns on, passes audio but does not add the effect. It has a high pitched squeal that varies tone depending on delay speed.

Its a analog delay pedal using four BBD (BL3208A), one compander (SA571D), one clock (cd4047), one TL082 and one 33178.

This pedal is prone to some issues (ESD), but i replaced the common faulty transistors and the problem remained. In fact, the original ones were still good (tested on component tester).

Anyone familiar with this pedal to give me some light?

Thanks, have a good day

Leandro
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Old 06-07-2021, 03:42 PM   #2
petehall347
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Default Re: MXR Carbon Copy High Pitched Noise

squeal could mean something is feeding back in the circuit
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Old 06-07-2021, 06:45 PM   #3
Camarada78
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Default Re: MXR Carbon Copy High Pitched Noise

Yes, but without the schematic it is rather difficult to find. much guesswork.

the schematic that floats around the web is for the ancient version of the Analog delay. not the carbon copy.
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Old 06-09-2021, 04:56 AM   #4
petehall347
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Default Re: MXR Carbon Copy High Pitched Noise

post some nice pictures of it
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Old 06-09-2021, 03:46 PM   #5
Camarada78
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Default Re: MXR Carbon Copy High Pitched Noise

mxr cc2.jpeg

mxr cc 1.jpeg
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Old 06-09-2021, 03:49 PM   #6
Camarada78
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Default Re: MXR Carbon Copy High Pitched Noise

MXR CC problem.rar

Above a .rar containing a .mp4 video of the problem (high pitched noise).
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Old 06-09-2021, 03:59 PM   #7
petehall347
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Default Re: MXR Carbon Copy High Pitched Noise

is it same with new battery ?
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Old 06-09-2021, 04:00 PM   #8
petehall347
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Default Re: MXR Carbon Copy High Pitched Noise

it sounds microphonic noise from somewhere ..try with new battery only .no power supply
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Old 06-10-2021, 11:35 AM   #9
Camarada78
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Default Re: MXR Carbon Copy High Pitched Noise

I tried new batteries, three different power supplies (two linear, one smps), all had the same issue.
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