Diagnosing a problem.

[PrimalScream91]

Hello all, I am new to the forum and need help diagnosing a problem.

I'm running my MP-1 into the power section of a Blackstar HT40 but when I plug the MP-1 into the return of the Blackstar I get nothing. Only after dimeing the output on the MP-1 and turning up the Master on my Blackstar will I get any noise. Even then all I'm getting is the occasional LOUD note coming out of the speaker.

I believe this could be a problem with the jacks on the back of the A/DA but I'm not 100% sure.

[Kim]

Yeah, those jacks do have a tendency to get brittle and fall apart.  I've seen a lot of them look ok on the outside and completely broken up on the inside.....
Have you opened it up and looked in there yet?

[PrimalScream91]

I have not opened it up yet, but that will definitely be my next step. I'll open it up and see if I can suss out the issue. I'll probably take pictures as well, so if I have any questions I'll post them.

[Kim]

I found an old pic I had taken of one of those MP-1s that had some real buggered jacks.  Hope yours aren't as bad as these were! 

[PrimalScream91]

This is what it looks like under the hood, I cannot see anything that looks particularly knackered, just dirty.

[PrimalScream91]

I'm also unsure of the year it was built. I did find this inside of it, I wonder if that's a date?

[MarshallJMP]

This looks like it's a late 89 early 90's unit, I saw a date code of 89 40 which means 1989 week 40.

You can also try to use the effect send as an output, so you could also try that one.And you can also try to plug in a headphone in the headphone out to see if the MP-1 works.

[rnolan]

Hey welcome to the depot  ,
Also maybe try into the Blackstar input (test it works with just guitar first) and keep the MP1 vol down. If Blackstar input is working, then MP1 main out(s), FX loop send and headphone out should all work into it (albeit not optimal but it will test them).

Wow it is quite dirty inside, needs a good blow with some compressed air, they looked like original tubes also ?

[Samuraipanda]

Kim, was that my MP1 that you modded? I remember you had to replace most of my jacks. 

[PrimalScream91]

Hey all!

This morning I cleaned out the jacks on the MP-1 as well as the Blackstar. The A/DA was quite dirty inside, so I figured i might as well test it to see if that was the issue. Sure enough the signal came in strong! Must have been an issue with all the buildup inside of that jack. Thankfully it wasn't anything too serious.

Thanks for all the help guys! It's nice to know there is a community dedicated to these old units.

As far as the tubes being original, I'm not sure, if there is any way to tell I'd be more than happy to take another look at them.

Thanks again!

[MarshallJMP]

So all okay now?

Looks like the tubes are the original National tubes.

[PrimalScream91]

Yep, all is good now!

I'll pop it back open and check the tubes, because now I'm curious!  :lol:

[MarshallJMP]

Take a look at the pic you posted 

Anyway these Nationals are just rebranded Chinese tubes as far as I can see.

[PrimalScream91]

Yep, Chinese Nationals.

NATIONAL
12AX7/ECC83
MADE IN CHINA

[MarshallJMP]

Never seen these before, the older MP-1's also had National tubes but these were not Chinese tubes.