Mxr Carbon Copy

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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blasq
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Post by blasq »

Hello,

I've been searching for schematic for Carbon Copy on net, but I didn't find anything.
anyone have a schematic for this box? Does it exist..?

Wojtek.

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Dirk_Hendrik
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Post by Dirk_Hendrik »

Yes it does. At MXR.
Considering the age of the CC I don't expect the factory schematic to surface soon.
Sorry. Plain out of planes.

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guiddruid
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Post by guiddruid »

found this hires gutshot on google;
https://media.photobucket.com/image/mxr ... 76.jpg?o=5

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charlietheunicorn
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Post by charlietheunicorn »

hehe, good look for creating this in DIY

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Nikifena
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Post by Nikifena »

Hi guys, I make 2 pictures of this pedal:


There are 4pcs. BL3208A. 2 of them is hidden under the pot.
All pots are 100k.

I think, that this pedal use classic delay topology
Attachments
carbon-copy-back.jpg
carbon-copy-front.jpg

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DocPlus
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Post by DocPlus »

What did the trimpots ?
I guess one allows to set the max delay time.

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Post by gena_p1 »

Trimpots for biasing input of BBD chips, and for fine tuning output (it gets from last stages).

Scheme seems close enough to green MXR delay

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whiskeytown
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Post by whiskeytown »

nice guttshots thanks dude :)

and that BL3208 delay chips, are these chinese and low cost, low quality chips?!

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miwanone
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Post by miwanone »

DocPlus wrote:What did the trimpots ?
I guess one allows to set the max delay time.
The trimpots are used to set the modulation depth and frequency (only when modulation is enabled ofcourse). I just sold mine but I always thought it sounded pretty good!

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1983ARC
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Post by 1983ARC »

Hi folks,

Now that this pedal has been out for a few years, I'm hoping that someone here might by now have either obtained or drawn out a schem for it - I need one for repair purposes (only) - any quality that's readable is fine, including hand-drawn. So if anyone is now able to post one on here, or PM me with a link or direct me to where I can find one, I would be most grateful.

Many thanks,
Mark.

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Post by blackbunny »

Still haven't seen a schematic for this anywhere, and I would be very surprised if there's one anywhere on the 'net, as MXR are notoriously secretive.

I've repaired a few of these that had the (quite common) switching fault where cooked SMD FET's result in no audio when the effect is switched in, or out, or in either mode.
Apparently the SMD FETs are susceptible to static electricity and can be easily destroyed while plugging and unplugging the pedal into your signal chain.

If this is your problem, you can try replacing the SMD FET Q10 with a J176 or J177 FET, as per the yellow arrows on the photo.

MXR issued a service bulletin a few years ago recommending that SMD FETs Q10,Q11, Q12 and Q13 be replaced with J177 FETs if the delay effect can't be turned on.
Attachments
MXR Carbon Copy JFETs.jpg

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Post by Dirk_Hendrik »

blackbunny wrote:Still haven't seen a schematic for this anywhere, and I would be very surprised if there's one anywhere on the 'net, as MXR are notoriously secretive.

I've repaired a few of these that had the (quite common) switching fault where cooked SMD FET's result in no audio when the effect is switched in, or out, or in either mode.
Apparently the SMD FETs are susceptible to static electricity and can be easily destroyed while plugging and unplugging the pedal into your signal chain.

If this is your problem, you can try replacing the SMD FET Q10 with a J176 or J177 FET, as per the yellow arrows on the photo.

MXR issued a service bulletin a few years ago recommending that SMD FETs Q10,Q11, Q12 and Q13 be replaced with J177 FETs if the delay effect can't be turned on.
I've had 2 or 3 on the bench that had the problem blackbunny describes above and were cured by replacing these FET's.
Sorry. Plain out of planes.

http://www.dirk-hendrik.com

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Post by Dirk_Hendrik »

whiskeytown wrote:nice guttshots thanks dude :)

and that BL3208 delay chips, are these chinese and low cost, low quality chips?!
For what it's worth, since it's a reply to an old post,
I've worked on multiple pedals with BL3208's and never encountered any problems that would suggest low quality (as in poorer than MN32xx Matsuhita chips).
Sorry. Plain out of planes.

http://www.dirk-hendrik.com

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Post by Bernardduur »

Would anyone know the value of Q2? (located underneath the mix knob??)

I have one on the bench that had worked before but now the unit won't turn on. I tested the unit but the TL062 gets no power. I can trace the V+ up until Q2, then I lose it. Q2 looks really bad (like burned) so my best quess was that Q2 was shot........ but what is it? Transistor? FET?
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Post by cluster »

Bernardduur wrote:Would anyone know the value of Q2? (located underneath the mix knob??)

I have one on the bench that had worked before but now the unit won't turn on. I tested the unit but the TL062 gets no power. I can trace the V+ up until Q2, then I lose it. Q2 looks really bad (like burned) so my best quess was that Q2 was shot........ but what is it? Transistor? FET?
transistor SMD 1R
A19T MOSFET P-CH 30V 4.2A SOT23

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Dr.Detroit
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Post by Dr.Detroit »

Anyone have the actual schematic for the Carbon Copy? Mainly interested in the BBD clock input driving mosfets. :hmmm:

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Post by chongwui »

I have read it somewhere that it is recommended to put a TVS diode across the J177. Anyone know the part number?

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Lani
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Post by Lani »

Best guess is any TVS with a VBR anywhere between 12 - 15v. Does the CC run off 9v?

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Post by chongwui »

Yes CC uses 9V

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Post by chongwui »

Lani wrote: 27 Jul 2023, 00:46 Best guess is any TVS with a VBR anywhere between 12 - 15v. Does the CC run off 9v?
The cathode of the TVS diode should connect to the Source or Drain of the J177?

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