![]() ![]() Replacement nuts and bezels for front panel sockets, knob to fit 6mm shaft of volume pot and the same but modified knob to fit the 1/4" D-shaft of the data encoder. Having said that, customers seem well chuffed with the results. So, while my hunt continues, I am forced to improvise. To find a knob that satisfies all of that and is available in two versions, one with a 6mm spline shaft fitting and another with a ¼” D-shaft fitting is well, kinda impossible. Finding a knob with the correct base diameter, height, ergonomics and colour is hard enough. ![]() The knob for the volume pot has a 6mm spline shaft and the knob for the data encoder has a ¼” D-shaft. There are two knobs on the front panel and although they look the same, the fittings are quite different. Of course, being discontinued for well over twenty years, Marshall don’t really hold a lot of spares for the JMP-1 and sourcing alternatives isn’t easy. As an example, I recently had a JMP-1 in, that had a data encoder knob which looked like it had spent half-an-hour in boiling water! The rest of the unit was pristine. People love their Marshall JMP-1s and I often get asked to supply more than a service. FANTASTIC!!!! Marshall JMP-1 looking, feeling and sounding like new. I put the lid back on, plugged it in and WOW! This machine looks, feels and sounds like it was made last week. If you need to initialise your unit, follow my guide here. Since the unit had just been bought, there were no user patches of significance so I initialised the memory. The back of the JMP-1 is simple but comprehensive. I cleaned the volume pot on the front as well as the sockets which although looked okay, hadn’t been touched for almost thirty years. I explained my Live Forever memory back-up battery mod’ to Stuart and he loved the idea so we went ahead with that. Just about to pop, the CR2032 as fitted in the Marshall factory twenty-eight years ago. I leaking battery could render your JMP-1 useless! Please do check out my post of Battery Acid Damage. It was obviously swollen and although still backing up the memory, was in desperate need of changing. The most disturbing observation when I took the lid off, was the back-up battery. Without modification, we know that the valves don’t really contribute too much to the tone of the JMP-1 but on this occasion, I decided to change them anyway, just so that everything’s nice and clean and so I dropped in a pair of cryogenically treated premium valves sourced from my good friend Derek at Watford Valves. The valves were original and electronically, they will probably last another thirty years. In fact, Stuart's JMP-1 became the first unit to have my 'Eclipse' bounce eliminator for the Marshall JMP-1 data encoder installed and you can read all about that here. I therefore, took this opportunity to design something that would sort this problem out once and for all. Marshall didn’t incorporate a hardware bounce eliminator into the JMP-1 and the outputs of the encoder, go straight into the processor. He also commented that the data encoder was skipping. Stuart said that he’d like the valves checked as well as the back-up battery. Marshall jmp 1 full#As such, I love working on them and enjoy testing the results even more! Having a Marshall JMP-1 in that needs a little attention is never tiring.Īnyway, last week a customer who had just bought one of these off eBay, took the initiative and sent it to me for a full service.Īlthough dated 1992 making it an original production example, you just wouldn’t guess it from the condition of the unit, it’s pristine. I’ve seen a few Marshall JMP-1s in my time and as some will know, I really do like this simple and straight-forward MIDI valve pre-amp. ![]()
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