Let's Get Technical > Troubleshooting Problems

MP-1 volume drop

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revhed666:
gday guys have had this problem for a bit and its preventing me from gigging my rack setup. random volume drops from the MP-1. i cant reproduce this problem and it seems whenever i try and troubleshoot it, it wont occur so i am yet to determine the MP-1 as the exact cause. i do run it in stereo with a marshall jmp-1 which does not experience the same issue. with no patch changing the MP-1 volume will drop a noticeable amount, sometimes flickering back and forth. sometimes it seems almost a permanent drop and i compensate by upping MP-1 master gain from 2.0 to 3.0 to even things out. it may stay like this for some days or weeks but sooner or later it changes back again and i readjust the patch levels. dont go crazy trying to work this out as i cant be absolutely sure its the MP-1 but i'm hoping u may have a solution. will try different tubes but they are mullards only a few years old and had very little use. cheers and beers

Soloist:
Hello revhed666,
What else are you running in your rack? I too run an MP1 and JMP1 simultaneously from time to time.
Are you using a mixer? Does it happen just running the MP1 alone?
To make it easier just post your signal path, it may be something other than the MP1.
For example I was running a Gmajor 2 after my pre's. The noise gate setting that worked great for the JMP1 choked out the MP1.
Or it could be an issue with the way you split your signal.
Either way someone here will be able to figure it out.

rnolan:
Hey mate, how'sitgoin ? (I'm assuming you're a fellow Australia  :wave: ). Hey no worries,we'll help you sort it out. A Soloist said detail your patching (this goes with that at Susan's...) and we'll work through it with you.  I can think of a few possible culprits (input jack (it takes the most wear and tear), output pot, needs a clean) but I need to know more how you plug it together (which will lead no doubt to further questions LoL).

Some basic maintenance though, clean input jack (well all jacks) and pots with some decent contact cleaner (may well fix it), a good thing to do regardless.  At this age it's worth changing out the input jack (well all of them really but that's a bit more ambitious).  Now we can't source them (MP1 input jack) anymore but you can do the input jack mod (changes the back input from line level to inst level) and replaces the front jack.

Cheers R

revhed666:
Yeh mate Aussie all the way ;)
Signal path
EMG 81/707》
Behringer rack tuner 》
digitech GSP1101 》
GSP 1101 mono fx loop out split with Y cable 》

LEFT: JMP-1 》DBX stereo 15 band EQ 》STEREO Sonic Crapuliser 》GSP 1101 loop return left 》Gsp 1101 line out left 》 Marshall EL34 100/100 Power amp left

RIGHT: MP-1 》DBX EQ 》Sonic Crapuliser 》 GSP1101 loop return right 》 GSP1101 line out right 》 marshall power amp right

Its a bastard intermittent problem that no amount of cable or jack  jiggling can reproduce. Hopefully its a tube. Obviously i thought the Y cable was a potential trouble spot. I bought every Y cable on ebay and worked my way through them. Of course the cheapest had the most solid connection. The sockets were slightly larger and loose fitting on the more expensive cables go figure.
U guys helped out before when a chip controlling the eq was faulty. I also upgraded the eprom at the same time. Will put tubes in now and try the maintenance tips and see what happens. And report back when i have something...or nothing haha

MarshallJMP:
Do you have a gain (distortion) or volume loss?

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