Category Archives: London

Gallien Krueger MB 150 Mains Transformer Replacement

By Frank | Published: June 30, 2021

The Gallien Krueger MB 150 is a popular bass amp, especially with double bass players. We recently had an MB150 in for repair with a blown mains transformer, GK part No. TTO-10879-02 (equivalent to TTO-10879-01). Unfortunatley, sourcing a replacement was tiresome. The UK distributor quoted 6 months lead time! I couldn’t find an off-the-shelf mains […]

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Upgrade PCB for Fender Blues Junior

By Frank | Published: June 3, 2019

The Fender Blues Junior (BJ) is probably Fender’s best-selling valve amplifier. However, it does have a number of poor design features; in particular the layout of the PCB on which the EL84 power valves are mounted. The EL84 is a well-designed valve. The high voltages on the anode (pin 7) and screen grid (pin 9) are located […]

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Electro Harmonix Big Muff Pi Repairs.

By Frank | Published: July 18, 2017

EH Big Muff effects pedal repair at JPF Amp’s London workshop in Denmark St.

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WEM / Watkins Copicat tape echo repair extravaganza

By Frank | Published: October 22, 2016

We had a bit of a WEM / Watkins Copicat repair extravaganza at JPF amps. Here’s a nice photo of three of the 8 (yes eight!!!) we had in for repair.   Great sound that can only really be done by a genuine tape echo.

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Fender Tonemaster (Tone-Master) Guitar Amp Repair

By Frank | Published: August 27, 2015

Although much credence is given to the notion that hand-wired amps are inherently superior to other methods of construction, this is certainly not always the case. Here’s the inside of a Fender Tonemaster amp, which as you can see is a total rat’s nest of wires. I dread to think what Harry Joyce would have thought […]

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MESA Carbine M9 Bass Amp Repair

By Frank | Published: June 15, 2015

Here’s some photos from an emergency repair I did for the band Swans. I got phone call from their tech saying that one of their amps. a MESA Carbine M9, had died with smoke emanating from the innards. Swans needed the amp turned around quickly as they were on tour. I said that this didn’t look […]

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Hughes & Kettner TubeMeister 18 Repair

By Frank | Published: June 4, 2015

I’ve had a few Hughes & Kettner TubeMeister 18 amps in for repair. This is an 18W fixed bias amp that uses 2 x EL84s in the output stage. These amps have a quite sophisticated biasing system that automatically adjusts the output valve grid voltage for optimum bias, and also shuts the amp down in the […]

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70’s Vintage Marshall JMP 100W Guitar Amplifier Repair

By Frank | Published: April 30, 2015

We often get 70’s Marshall JMP amps in for repair; these are excellent rock amps and are still very good value for money. Ahe major issue with these amps are the voltage and impedance selectors which are prone to falling out. Someone had done a really good job of wiring the mains selector in this […]

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Vintage 70’s Ampeg SVT 300W Bass Amplifier Repair

By Frank | Published: February 2, 2015

Here’s a rare example of a 70s Ampeg SVT that I had in the workshop. Introduced in 1969, the SVT has, rightly, gained the reputation as one of the greatest bass amp ever made. Indeed, even today the SVT is the industry standard bass amp for live work. However, working on these amps is not […]

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Fender Blackface Deluxe Reverb Repaired By JPF Amplification

By Frank | Published: January 8, 2015

We’ve repaired hundreds of vintage Fender amps, and it’s always a pleasure to get these classic amps back in tip-top working order. It’s a testimony to Leo Fender that so many Fender amps from the 1960’s are in use today. Here’s a picture of the inside of a vintage 1960’s Fender Blackface Deluxe Reverb we […]

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