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[anto84]

He can barely remember the software version (1.38 of course) so the previous ones was the max I can pretend from him..
The fact that touching the input jack, the volume came back to normality what could it mean?

[MarshallJMP]

Well if it's a V1.38 it could be the input jack,most of these start to fail.So it's possible if you change it the problem will be solved.Problem is i can't find them anymore so it's best to replace it with the rear jack mod.

[anto84]

Hi thanks for the answer.
So if the input jack is the problem..can't be replaced with a similiar one with the same specs? I'd be happier not modding by myself..I'm a mess with soldering and wires! 

[tomy]

Hi Anto, sounds good  for you : you get a mp1  for cheap and soon it's gonna be fixed
You lucky guy ! 

[rnolan]

The rear jack mod (http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm) is reasonably easy to do and any tech would have no problem doing it for you

[anto84]

I ended buying the Mp1 so in a few days it will arrive at my destination.
I'll be able to provide you way more detailed information regarding the problem of the unit...and I hope we can figure it out toghether the solution! ...I'll be your eyes..you all guide my hands please!! 

[MarshallJMP]

Ok we'll get it in working order 

[anto84]

Hi guys..Mp1 arrived at home 1 hour ago. I opened it to remove some dust. I plugged my guitar with old tubes (to eliminate tube related problem from the possible cause of the volume drop)
I'm playing trough it and I confirm that the problems are not the tube..the volume drop happen only when touching the frontal output knob (so it's not, I suppose a inpunt jack problem). The knob make the some noise of a old guitar tone pot ..it begins to scratch every time i touch it and it it goes to a position where the mp1 is totally muted...then you move a little bit the knob and the volume stays until next "finger touch" of the knob.

So it's not a volume drop...as I thought... it's not lowering gain/volume thing but a totally disappearing volume thing.
Suggestions?

UPDATE: the input jack has some problem too. With the jack in if I hold the jack down from the outside with my hand from the othe volume go away too.... I

[MarshallJMP]

Well it seems you need a new front vol pot and a new input jack.

[anto84]

And where I can find they? The effect send/return knob too is scratchy when moving....

[MarshallJMP]

Well if you want i have these.

http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm

[anto84]

I'll try intensively the unit for a couple of days to see if the problem happens when playing with the guitar in a rehearsal situation.
What I noticed in a 2 hour test is that if I don't touch the knobs there are no problems...
If the scratches/drop volume continues to show only while moving the output and send knobs maybe I can live with that, cause when I leave they in position the unit is perfectly working.

Oh..just another question..Look at the picture of my Mp1..do you see some mods made or does it looks stock? (I'm asking cause the unit comes with a short 13,7 inch cable and I remember that the Mp1 I had 10 years ago was way more noisy than this one...
Thanks!
]http://

[MarshallJMP]

Looks stock to me,can't see the tubeboard.Can you take a pic of that one?

[anto84]

Of course! Here's the pic. Loaded with a brand new matched pair of jjecc83s
Can I ask you how you use the send/return level knob on the rear of the Mp1? It is better to leave it on the max and and adjust the level from the effect or better set the multieffect (pedal or rack) level at max and adjust the Mp1 level to taste?
I noticed an increment of +- 1 dB of the overall volume leaving the Mp1 loop lepel knob at max with loop in even when the effect is bypassed (think of a delay pedal when you press it to bypass). To have the same volume it seems you should set the Mp1 level knobs to 9.5/10...funny

[rnolan]

The MP1 loop is a tricky beast, some like it some don't.  It's a serial loop (inserts into the signal path), and the knob is a dual ganged pot so when you turn up the send it turns down the return and vs versa. Also there is always signal on the send, switching it in or out toggles the return. Try setting it half way and adjusting the FXs' input and output to suit.  Adjust it such that there is no increase or decrease in overall level when it's switched in/out (unity gain)