MP1: Overdrive2 Doing Nothing

[klaus dibbelt]

Hey, and thanks for allowing me in here!

Hadn´t used my MP1 for some years, and have started toying around with it again. Everything´s great and fine, but:
In Clean and Distortion Voicings the Overdrive2 trim doesn´t change anything about the sound (while in SolidState Voicing it does what it´s supposed to do).

Any ideas?
TIA
klaus

[RobbHell]

Check your  (H) wire to the main board and tube board. It controls OD2.  Check that wire and get back to us.

[klaus dibbelt]

Thanks for the quick response, RobHell!  :thumb-up:
I´m not a technician, though. Could you tell me what an/the H-wire is, and how to identify it?

[MarshallJMP]

It's the shortest shielded wire (usually brown or yellow) going from the tube board to the mainboard.It's connected next to V2 (tube)

[klaus dibbelt]

Ok, I´m going to check this first!

[RobbHell]

Awesome MJMP's on it! Yea the schematics clearly show and will help a lot. Don't be scared. Should be an easy fix..
Hope all.works out well.

[klaus dibbelt]

Hey,
so I finally opened the MP1 and found the - I guess - H-cable. See the attached pic. Looks fine to me.
Now, what am I supposed to check about it?

[RobbHell]

The H Wire connects to T2 trimpot. How long has this unit been stored?

[RobbHell]

The H Wire stock controls the 3rd gain stage (V2). Grab a volt meter and checking your values to (V2) the schematics  will give the locations and the given value for that location.

[RobbHell]

Don't your exact location in Germany but MJMP could a super close drive. Plus you can hear his mods.

[RobbHell]

Also take a look at the F wire. Could you tell us the history of this unit.

[klaus dibbelt]

Hey RobbHell,

I´m afraid this diagnostic work is beyond my technical capabilities. :(

MJMP appears to live in Belgium which would be quite a trip from here...

I guess the best would be to hand it over to the guy whom I let fix my tube gear, along with your hints and advice.

I bought the used MP1 15-20 years ago. Used it for a while (and I know for sure that V2 was working back then), and later had it sitting in my rack only for the chorus.
It must have been sitting around without being regularly used for about 10 years, even though I occasionally dug it out and toyed around with it a little - without doing much editing. So I can´t say for how long V2 has been disfunctional.

It´s version 2.01.

Then again, I am wondering if I am missing something important without the second gain stage, since V1 seems to give me way more gain than I´d ever actually need. (?)

Also take a look at the F wire. Could you tell us the history of this unit.

[MarshallJMP]

Hey,if you want you can ship it to me but first let's try some things first.

Look at the pic,can you measure with an ohm meter the resistance between the 2 blue arrows,should be around zero ohms.

And can you take a pic of the component with the purple arrow.It's hard to see but it could be those 2 connections on top are connected together.

[RobbHell]

I know they do go bad... MJMP how many VCA's have you had to replace? Probably more with the MP2 i'd assume. I've just never had one fail on me but I know they do crap out from time to time.

[klaus dibbelt]

Man, this is an awesome group! You guys are so helpful and supportive!  :thumb-up:

Ok, my ohm-meter (when I dial in the 200Ohm-range) displays 00.2 between those points. (Which is "close to zero", I guess).
But the other thing indeed might be more significant: the wires coming from the component seem to touch each other (which the ohm-meter seems to confirm). So...should I bent them from each other, for starters? (Close up pic soon to come).

Hey,if you want you can ship it to me but first let's try some things first.

Look at the pic,can you measure with an ohm meter the resistance between the 2 blue arrows,should be around zero ohms.

And can you take a pic of the component with the purple arrow.It's hard to see but it could be those 2 connections on top are connected together.