Author Archives: Frank

Fender Pro Junior Hum Investigation

The Fender Pro Junior amplifier is popular amplifier; it sounds good, is portable and loud enough for smallish gigs (the sort I play for example!) if you don’t want ultra-clean. It does have an Achilles heal which is that it prone to be noisy, often to the point that players find their amps unusable, so […]

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Gallien Krueger MB 150 Transformer Replacement

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 trying to source a replacement was tiresome. The UK distributor quoted 6 months lead time, and the only other […]

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MESA M-Pulse 360 Bass Amp Repair

We recently had a MESA Pulse 360 bass amp in our new workshop for repair, with a fault description that it was powering up but not passing any signal. I’d repaired an M-Pulse 360 last year with a identical fault condition, so we wondered whether the fault in both amps was being caused by the […]

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JPF Amplification now at 5 Denmark Street.

We have relocated our work shop to number 5 Denmark Street, WC2H 8LP.

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Upgrade PCB for Fender Blues Junior

The Fender Blues Junior (BJ) is probably Fender’s best-selling valve amplifier. However, it does have a number of poor design features, not least the layout of the PCB on which the EL84 power valves are mounted. The EL84 is a well-designed valve as the high voltages on the anode (pin 7) and screen grid (pin 9) are […]

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Electro Harmonix Big Muff Pi Repairs.

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

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Ibanez TS-808 Tube Screamer Reissue Switch Repair.

The Ibanez TS-808 Tube Screamer is, rightly, regarded as a classic pedal, and has been reissued by Ibanez; this is lucky as an original TS-808s will set you back several hundred pounds.     Unfortunately the switches on the reissue (and indeed the originals), are not that robust. This pedal came in with a broken […]

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WEM / Watkins Copicat tape echo repair extravaganza

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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Leslie 122 Relay Repair

Here’s an emergency repair I did for a Leslie 122 cabinet. The fast / slow relay had died, and I needed to find a solution with parts from Maplins! The fast / slow replay relay switching is quite interesting in the 122. The cabinet is connected to the organ by a 6 pin connector, however […]

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Fender Tonemaster (Tone-Master) Guitar Amp Repair

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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