ADA Preamps > Original MP-1

Fixing Richards 240v MP-1

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Tim:
first post here ,thanks Richard.Richard has kindly supplied all the service info for it ..The MP1 was getting to the ada screen and locking up . I checked the power supply rails and all were o.k. 15v / 5v and others seemed o.k.The  caps in the area o.k. with esr meter I have not checked with the cro for ripple but I decided to heat the board up in the power supply and main area and it booted up and started working again. So still guessing caps somewhere at the moment.Has anyone else seen this fault ?no sense in reinventing the wheel :-)

In the morning I'll see if its locks up again when cooler and try and pinpoint the area better - I think its most likely where the tubes are as caps look like they have been cooking up a bit with the heat.
Will keep you posted . cheers.

rnolan:
Go Tim, so it worked again  :crazy: ,  when I bought it he said it wasn't working but the US one he got to replace it for gigs was working fine.
So I tried them both when I got them home and it worked for a little while which got me excited, then it stopped responding to midi patch changes  :facepalm: .  I fiddled with it a bit, puled the CPU and EPROM chips out and put them back in which seems to initiate a full diagnostic boot (based on doing it with one of MB-1s) but that didn't help.

So MJMP it was getting stuck in the boot sequence, got as far as displaying ADA and went no further.  You may not remember when we talked about this ages ago  :dunno: and I got a zap of the board (which surprised you) and I cut my finger on the underneath sharp component ends as I pulled my finger out. So I went to bed and haven't touched it since until now.

Tim:
Plugged it in again this morning- still working ?  :o
I'll keep it on the bench for a while and see what happens.( intermittent problems are a pain! )
n.bYou must have touched the tubes supply or the 240 input to get zapped.  Wakes you up doesn't it ;-)

rnolan:
Hey Tim, well that's strange, well while it's working, plug a gitar into it, run the a/b/ outs into a stereo amp/speakers and try the factory presets, patch 1 is Marshall.  Alternately you can run one channel into your JCM500 flick that top switch so it's instrument level, you'll need t play with the amp eq a bit t get it flat.
If you play it for a while, change patches IIRC the first 4 banks have factory patches (a variety of sounds for various guitars)

When I got zapped, I had my hand/finger under the CPU pushing up while I pushed it in/down from on top, so it was strange as there shouldn't be any big voltages there.

MarshallJMP:
Midi, maybe a bad contact in the ribbon cable connectors, have you tried to pull it out and put it back in again?

Another thing to try is replacing the diodes D38,D39 these can fail sometimes giving an unstable 5V to the µP at startup.

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