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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.

Carlsbro Repair – Cobra 80

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Carlsbro Repair

Carlsbro Repair – Cobra 80

The owner of this Carlsbro repair complained of an intermittent crackling and occasional dropout. The fault was found to be within the power supply – a not uncommon source of trouble in bass amp repairs.

One of the pins on the bridge rectifier had developed a hairline crack through the pin. It was mounted to the rear panel, and when the panel flexed, the power connection arced, creating the described noises.

This repair was easily finished within the diagnostic period. When I find a quick fix for customer’s amps I always perform a routine ‘mini service’ to ensure the customer gets their money’s worth.

They’re not bad little amps these old Carlsbro Cobras – I gigged for many years in a jazz band using a Cobra 45!

If you have a Carlsbro Repair job that needs doing please, get in touch.

MXR Repair – Carbon Copy

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MXR-Repair

This MXR repair, a Carbon Copy, was a simple fix. ESD (static) had destroyed 3 switching transistors used in the bypass circuitry. After identifying the fault I contacted MXR to find the part numbers of the damaged items. MXR are aware of the issue and recommended a modification to significantly reduce the likelihood of a repeat problem. I’ll take this moment to thank the guys at MXR/Dunlop (partic. Derek Jones) who provide excellent tech support.

UPDATE: 2016

I’ve since repaired many of these and I now keep the parts in stock ready for the next MXR repair.

As you can see on the photo on the other delay pedal repair page , this MXR uses surface mount technology (SMT). Some find this a little fiddly to repair and many repairers won’t touch it, but I actually prefer it to through hole!

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/

MXR Repair – Carbon Copy

If you have a an MXR Repair or a Dunlop Repair job that needs doing please, get in touch.

Marshall Repair – JCM2000 DSL100

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Marshall Repair

This Marshall Repair was brought to me with one of those sneaky ‘hard to find’ problems. The amp was blowing fuses when the customer was playing it. He’d taken the amp to another repairer who hadn’t found any problems. Unfortunately the amp continued to blow fuses.

Guitar amplifier repairs of this kind often have to be treated in a different way. After an initial examination, opening up the amp and checking for any burnt components or loose joints I placed the amplifier on soak test. This involves playing a representative signal through the amp into a dummy load in the conditions that the amp was in when it was blowing fuses. During this soak test I observed that under certain conditions one of the power valves was sparking internally. I swapped the set of valves, re-biased and then placed the amp back on soak test. Since the amp wasn’t blowing fuses or sparking any longer, I decided that it was ready to go.

If you have a Marshall repair job that needs doing, please get in touch via the contact page.

Laney Repair – VC50

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Laney Repair

Laney Repair

This Laney Repair was a mixed bag of several issues! The amp is a VC50 – 5 12AX7 valves and 2 6L6s in the output. This particular specimen has a strange an whine present whenever channel A’s spring reverb was used, also a faulty gain control on channel A, an intermittently working footswitch and a rather noisy pre-amp stage.

Since the amp is old and worth under £300 in used condition I advised the customer that an in depth repair might not be in his best financial interests. We agreed a price limit, within which I was able to fix the faulty gain knob, the reverb oscillation and the intermittent switch. This then allowed the customer to sell the amp in working condition and he put the money towards a new amp that suited his purposes more closely. Everyone was happy!

Forgot to photograph this one – apologies for the stock image!

If you have a Laney repair job that needs doing, please get in touch via the contact page.

Dual Rectifier Repair – Mesa Boogie – Ampworks, Newark

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This Mesa Boogie Dual Rectifier Repair is one of the more unusual problems I’ve come across. The Mesa was brought in with very low (and unpleasantly distorted) volume and blowing fuses. I tracked the issue to the output circuitry and checked for all the usual failures with no result. The output transformer looked to be the faulty component but the issue turned out to be a faulty component that was loading down the 4 ohm input with a low impedance. Component changed and the amp springs back to brutal METAL life!!

UPDATE 2016:
Mesa Boogie repairs are among the most difficult jobs to do, partly because of the complexity of the amp (which makes for a fantastic product) but also because they design their PCBs in a way that aren’t very friendly to repair. I’ve done many mesa boogie amps though (you can read about others here) and they are always worth fixing!

Mesa Boogie Repair

If you have a Mesa Boogie Dual Rectifier repair job that needs doing, please get in touch via the contact page.