delay repair

MXR Carbon Copy Repair

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Carbon-copy-repair

I’ve talked elsewhere (here and here) about Carbon copy repairs and the ESD issue that causes the problem. I’m just going to take a moment to discuss the symptoms that show the problem in the carbon copy pedal.

As I understand it, this issue has been fixed in new production units so if you’re buying, don’t let it spoil your enjoyment of a great little delay unit.

The issue is with the switching circuit. Mxr use a circuit related to the millennium bypass. This is a true bypass circuit that uses clever circuitry to operateb the LED without using a chunky and unreliable 3PDT SWITCH.

If you see a carbon copy that works in bypass mode but doesn’t switch in the effect or illuminate the effect LED then the carbon copy had fallen full of the ESD problem. The modulation LED will probably still work.

I use the same method as the service engineers at MXR in the USA to fix this issue. I replace the faulty components and across each of fit a special component that blocks transient voltages such those caused by static buildup. As I see a lot of these, I’ve started to keep stock of a carbon copy ESD fix kit. The components are less than 2mm wide so it takes an experienced hand to fit them.

UPDATE: 2017

The MXR ESD repair kit is now available for sale at www.rsdsound.co.uk. If you’re an experienced repairer and skilled with SMT repairs then you can purchase this kit. If in doubt, just post it to me and I’ll sort it for you.

http://www.rsdsound.co.uk/product/mxr-carbon-copy-esd-repair-kit/

If you have a carbon copy repair for me, please get in touch. You can drop the pedal in, or post it to me.

MXR Repair – Carbon Copy

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MXR Repair

This poorly delay pedal repair had the same problem as this MXR repair job from last year. This is a known ESD fault with Carbon copy delay pedals ‘of a certain age’.

As you can see on the photo, this Delay pedal uses surface mount technology (SMT). This can be a little fiddly to repair, but I often prefer it to through hole!

The faulty items are JFETs Q10-13 (the little 3 pin triangles. As you can see I’ve fitted a tiny Transient suppressor between two legs of the replaced JFETs. This should guard against recurrences of the same problem.

I’ll take another moment to thank the guys at MXR/Dunlop (partic. Derek Jones) who provided excellent tech support the first time I came across this issue.

The owner of this pedal plays harmonica through it with the Whitefern Mountain String Band. If you’re passing through South Wales, then check them out!

UPDATE: 2017

The MXR ESD repair kit is now available for sale at www.rsdsound.co.uk. If you’re an experienced repairer and skilled with SMT repairs then you can purchase this kit. If in doubt, just post it to me and I’ll sort it for you.

http://www.rsdsound.co.uk/product/mxr-carbon-copy-esd-repair-kit/

If you have a delay pedal repair or a Carbon Copy Repair please get in touch.