Author Archives: Frank

JPF Amplification repairs at Sweet Amps in Hackney E9 7PX

Feedback from customer says it is getting increasingly harder to get amps in the JPF Amplification workship in Denmark St. Congestion charge, ULEZ, lack of parking, and the fact we are on the second florr are the main reasons given. To provide another option for our customers, we are now taking in repairs at Sweet […]

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Investigation Of Noise In Fender Pro Junior Guitar Amplifier

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. Unfortunatley it is prone to being noisy – often to the point of unusability – so we did some investigation into the sources of noise […]

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Gallien Krueger MB 150 Mains 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, 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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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; 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.

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. Ibanez have now reissued the TS-808. This is fortunate 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 switch. In […]

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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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