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Hi all, I have a JMP1 saga ...
It blew a fuse while in use, and some discoloration on the power transformer. The current across the fuse socket was ~200 mA without preamp tubes so I checked it unloaded, and yeah, the short was internal. Nothing else looks crispy.
Power transformer has been replaced with a new one from Plasma Music LTD, and the current through the fuse socket is a much more reasonable ~40 mA. I replaced the battery as well while I was in there. But now there is no display and buttons / rotary encoder do nothing. The unit still passes signal from input to the headphone jack on the front.
I've checked everything I can think of in power supply world. Linear regulator outputs all look correct, I've had a scope on them and there's no bounce or anything so apparently filter caps are fine. I've done the reset, holding OD1 + CL1 and restarting. No change. IC power pins are getting proper voltage. It -seems- like the transformer swap was successful and something else has gone wrong.
What else is worth poking here? If I somehow killed the EPROM / SRAM / processor, is there anything to be done there? I'm open to suggestions. I like this thing, would prefer not giving up!
Thanks
N
It blew a fuse while in use, and some discoloration on the power transformer. The current across the fuse socket was ~200 mA without preamp tubes so I checked it unloaded, and yeah, the short was internal. Nothing else looks crispy.
Power transformer has been replaced with a new one from Plasma Music LTD, and the current through the fuse socket is a much more reasonable ~40 mA. I replaced the battery as well while I was in there. But now there is no display and buttons / rotary encoder do nothing. The unit still passes signal from input to the headphone jack on the front.
I've checked everything I can think of in power supply world. Linear regulator outputs all look correct, I've had a scope on them and there's no bounce or anything so apparently filter caps are fine. I've done the reset, holding OD1 + CL1 and restarting. No change. IC power pins are getting proper voltage. It -seems- like the transformer swap was successful and something else has gone wrong.
What else is worth poking here? If I somehow killed the EPROM / SRAM / processor, is there anything to be done there? I'm open to suggestions. I like this thing, would prefer not giving up!
Thanks
N
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