ADA Depot - A Forum To Support Users of ADA Amplification Gear

Please login or register.

Login with username, password and session length
Advanced search  

News:

Let us never forget our beloved founder - RIP Jurrie, we all miss you very much

Pages: [1]   Go Down

Author Topic: Low Volume & Unpleasant Distortion in one output channel.  (Read 7093 times)

0 Members and 1 Guest are viewing this topic.

Auntie Ada

  • Newbie
  • *
  • Offline Offline
  • Posts: 8

What a coincidence.....I just joined this fab forum and my MP-1 starts to go wrong. On one side of the stereo output the volume has all but disappeared and when I play hard there's this spitty, farty distortion on that side only (even on SS setting). Is this indicating that one of the valves is going ? There's no microphonic squealing at all.....yet.

Help, dudes !
Logged

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4702
    • marshalljmpmodshop.net

Is this a V1 or V2 mp-1 (top switch or not)?

Plug in a stereo headphone in the headphone out jack and see if both channels works or not and let me know.
Logged

Dante

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 2124
  • Nothing more uncommon than common sense
    • The Best Cover Band In Sacramento

What a coincidence.....I just joined this fab forum and my MP-1 starts to go wrong.

I promise, it was only coincidence. I do not have a big enough brain to devise a device that makes your MP-1 go wonky as soon as you join. Don't you worry man, somebody in here will get you straight, they always do ;) and you're family now.

Auntie Ada

  • Newbie
  • *
  • Offline Offline
  • Posts: 8

Thanks guys, I feel right at home.
I think it's a v1 but I'm at work at the moment so I'll check when I get home and come back to you.
Watch this space...
Logged

Auntie Ada

  • Newbie
  • *
  • Offline Offline
  • Posts: 8

There's no top switch that I can see. I tried the headphones test (good call, Batman) and it sounds a-OK in the 'phones.
Does that give anyone a clue ?

 :dunno:
Logged

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4702
    • marshalljmpmodshop.net

Ok,could be opamp U10 and/or C49 if it's out A or C48 if it's out B,and another thing (but i doubt it) the front volume pot.
Logged

Auntie Ada

  • Newbie
  • *
  • Offline Offline
  • Posts: 8

Ok, thanks JMP, I think I need to look up my friendly neighbourhood MP-1 guy (I'm not even sure he's still in business) and see if he can sort me out.....if my piggy-bank has enough money in it ! Your help is was much appreciated.
Logged

rnolan

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 5998

Ok,could be opamp U10 and/or C49 if it's out A or C48 if it's out B,and another thing (but i doubt it) the front volume pot.
@MJMP Would the HP out still work if the front vol pot is playing up ?
@Auntie ADA, if (as you say) HP out is fine, you can use that as your stereo out to keep you playing (it has some top end reduction (like a cab sim) so you may need to adjust eq a bit (add tops) but it will keep you playing for now. Use an insert lead (stereo jack to 2 x mono jacks) but careful with HP out, it has LOTs of gain (keep it less than 12 o'clock). I it were me, I'd get the tech to change out both caps and the opp amp (C48, C49 and U10). And I suspect MJMP (as usual) is on the money).

So no top switch = V2 (so you know what schematics to grab for your tech) although MJMP has already posted the one you need ? or check the vault.
Logged
Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

Auntie Ada

  • Newbie
  • *
  • Offline Offline
  • Posts: 8

All good advice. Many thanks for all your input.
Logged

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4702
    • marshalljmpmodshop.net



[/quote]@MJMP Would the HP out still work if the front vol pot is playing up ?
[/quote]

Yes because the HP signal is tapped before the front vol pot.

Another thing to try which is very easy to do is pull the red connector (near the front vol pot) and put it back in,just to make sure it's not a bad contact in the connector which i doubt but you never know.
Logged
Pages: [1]   Go Up