MP-2 Channel B intermittent

[rnolan]

So one of my MP-2s in my studio rack is having intermittent issues with channel B.  Unfortunately, of the 2 I have in the studio rack it's the best sounding, the other MP-2 is working fine but just doesn't sound as sweet.

So when I turn it on it works fine for a while, then channel B output stops (on both the main outs and the cab sim outs). I cleaned the rear switches and jack sockets hoping it would fix it but it didn't .  Turning it off and back on channel B works again the drops out after a few minutes.  On one occasion, after turning back on ch B worked but sounded "digital" for a bit then settle down.

So I'm guessing this is a problem around where the signal goes stereo (around the chorus).  And may have implications for the noise Dante is getting on his MP-2 B channel??

[rnolan]

Update, after the dropout issues on the weekend, I left the MP-2 powered up for 2 days (ish).   Tonight I turned it on and all worked fine, no dropouts, just sweet sounding MP-2 and my guitar student (who just bought a MP-2 rig almost the same as mine) ran up a clean sound from scratch on this/my MP-2  trying to emulate an acoustic guitar sound (using the 4x12 cab sim outs into my studio monitors).  He added a tiny bit of mids to bog standard (flat) crystal clean and he was mostly happy.  Upside for me was the MP-2 worked fine, no dropouts on chan B .  Hope it stays that way.

It was also a good exercise for him to learn how to program his MP-2.

[Dante]

I'm glad it's working....I don't like that you didn't really figure out whassup tho....

Why would leaving it on for two days help? I don't get that part

[Harley Hexxe]

Burning in your new tubes Dante.

[rnolan]

Hey Dante, I agree, why was it fixing up when power cycled and why after such a long power on has it fixed itself , well for now anyway. Strange behaviour, particularly when one of the power cycles got B working again but it sounded very digital, only one time.  Moreover, when I was doing those power cycles  (I did a few), it always worked again for a few minutes.  So thinking it may be related to heat, I left it on late Friday night.  I turned it off late Sunday, when I fired it up Monday night it worked fine all night.  I hope it stays working, obviously I'll be hearing it....

The tubes in that MP-2 haven't done allot of hours, but they are burnt in.

[Dante]

Burning in your new tubes Dante.

AH! New tubes, I missed that part

[Dante]

Richard says that ain't it....weird (?)

BTW: I need to figure out that hiss in my MP-2 when I get it back in-house (it's at the practice pad)....I just figured out how to run my Classic stack in stereo (don't know why I didn't think of it before) and I wanna try it with the MP-2. I simply ran out of ChB on my FX chain into the FX return B on the Classic (I usually run into the FX return of another amp), then hooked up the stage outputs to the MT-100 inputs. Voila! Stereo rig - I need to update my signal chain diagram ;)

[rnolan]

Hey Dante, yeah whatever is going on in that MP-2 it isn't tubes (chan A is fine).  I was having some tube issues with my live rack MP-2 when I swapped out some (still quite new) NOS ADA Chinese tubes for a pair of Mullard LPs (which are sooo much nicer in it).  Initially V2 was "slow tremolo-ing" a bit, not much but noticeable.  It reminded me of one of you previous posts where the volume was varying.  It was only on voice 6 and up (using OD2).  It seems to have settled, initially I thought I had a dud tube. So now burnt in it seems.

For me, the MP-2 really comes alive (as do MP-1s) in stereo, I suspect you'll love it (even with a bit of hiss).  But that hiss is a problem in yours.  You could try what I did that (for now) seems to have fixed ch B drop out issue on my st rack MP-2, i.e. power it up for a couple days

So good news is while posting this, I plugged in and , MP-2 is being good .  So it was just on a default program, crystal clean (voice 1), Dr and Mas 50/50, everything else flat.  And it sounded awesome, chan B is still good.