Tag Archives | Valve amp Bias

orange-amp-repair

Orange Amp Repair – Rockerverb 100 MKII

This Orange amp repair is a particularly shocking example of an amp which someone has attempted to repair without really having an understanding of what they’re doing. The customer brought it to me with two issues: a broken reverb (victim of the botched repair) and an intermittently faulty gain channel. I started out by performing […]

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Marshall-JCM900-repair-2 copy

Marshall JCM900 repair – Ampworks Newark

This JCM900 repair arrived after the owner found that it was lacking in volume. It’s a 2009 unit, two channel, with a 2203 type circuit on channel A and a higher gain circuit on channel B. The problem appears to have been with the amplifier bias. Although the valves were matched, the bias on this […]

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HT-CLUB-40-Repair

Blackstar Repair – HT40

Recently, a Blackstar amp repair was brought to my workshop in Newark. The amp was an HT40 (the Club 40 combo) in working condition, but the owner wanted to try a new set of EL34 power valves in the amp. He selected a matched pair of Tung Sol with slightly higher gain (according to my […]

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Mesa Boogie Bass 400+ Repair

Mesa Boogie Bass amp Repair

This mesa boogie bass amp repair had the highest power valve count I’ve seen. The amp uses no less than twelve 5881 6L6 valves! Like the recent fender amp repair this valve amp was blowing fuses. Also like the fender repair, the failure was down to a damaged power tube. Two in fact. Much is […]

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Marshall-jcm2000-repair

Marshall JCM 2000 Repair – TSL 100

Marshall JCM2000 repair I get quite a lot of the JCM2000 series in for repair – both DSL and TSL. I think it’s because they were so popular, rather than any endemic issues. This particular JCM2000 is a TSL100, the triple super lead model. I’m writing the blog post quite a while after the repair […]

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Cornford Repair

Cornford Repair – MK50 ii

This Cornford repair came in for a service. Conford amps are often beautifully constructed amplifiers that sounds as good as they look! The owner uses the MK50 ii bias switch to use 6L6 and EL34 valves. He was using E34Ls (different to EL34s!!) and wished to have the valve amp biased to move the EL34s […]

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Hughes & Kettner Repair

Hughes & Kettner Repair – Tube 50

This Hughes & Kettner repair is a tube 50 brought in for a valve amp bias. The Tube 50 is a fixed bias amp, meaning you need to bring the amp to a tech to have it adjusted (confusingly!!) by a technician. The opposite of fixed valve bias is cathode valve bias. Confusingly cathode bias […]

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Laney Repair

Laney Repair – GH100L

What is it with laney amps that makes me forget to photo them? This Laney amp bias GH100L just needed its bias adjusting to accommodate a new set of EL34s. The GH100L is a fixed bias amp, which means the bias is adjusted (and quiescent current is fixed) by a technician. The opposite of fixed […]

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Marshall Repair JCM2000 DSL

Marshall Repair – JCM2000 DSL100

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 […]

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