Let's Get Technical > Troubleshooting Problems

MP1 1.38 - Is my Chorus failing???

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skarkowtsky:
Hi Harley,

I was just inside a couple of weeks ago to swap out the tubes. Everything looked intact, no leaky or ruptured caps, no corrosion or damaged components.

I have a theory about what might have caused this. The unit just beneath the MP1 is a Roland SRV-2000 which throws A LOT of heat. Although it's the normal operating temp for that unit (even states it on the casing), I think it slowly cooked the MP1 over time.

I'm about to re-rack with a blank slot between the two. But yeah, I reached out the JMP, waiting to hear back.

skarkowtsky:
UPDATE

I appeared to have fixed it. After opening the top and bottom tonight, I did a thorough visual inspection of every component, but no evidence of physical failure. This was also the first time I've seen the bottom of the PCB.

I gave everything a light dust with an old badger bristle lathering brush, while I was in there. For the sake of experimenting, I rolled the new tubes and the old JJs I replaced a couple of times, and to my surprise the chorus sounded great. No warble unless I really push the rate frequency, as expected. Perhaps there was some oxidation or dust in the sockets??

I did notice the large trace on the bottom of the PCB is blistered in spots, though the trace is intact, not tears or splits. Please have a look at the photos and let me know if this is a concern.

I'm not sure if this fix is permanent or temporary, but I'm happy for now.

Thanks!
John

Harley Hexxe:
   Hi John,

             You rolled tubes and it fixed the chorus issue?!? The tubes don't have anything to do with the chorus as far as I know, but it does narrow down the area in the preamp where the issue is.

             If the traces aren't lifting off the PC board, and they aren't broken, it shouldn't be a concern. It does sound like that might be related to the heat issue you mentioned. The preamp tubes do give off heat too, so I always try to leave the top of the preamp open and try to get some kind of ventilation into the back of the rack for that reason.

             Sorry I can't be more helpful about this.


Harley 8)

skarkowtsky:
Yeah,I know it doesn't make sense, lol!
Maybe the light cleaning did it, or when I brushed the board I moved something back into place?? I really don't know. If it goes wonky again, out for service it goes.

I'm thinking of replacing the Roland unit with something that doesn't get as hot, too.

Harley Hexxe:
Hi John,

         You know, theoretically, no solid state device should ever get so hot that you can't keep your hand on it for 10 seconds without pulling it away.

         If that Roland unit gets that hot, it may have some kind of issue going on. Just saying.


Harley 8)

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