Incoming Marshall 74 JMP 50 - some questions...

Everything from original vintage Marshalls to reissues.

Moderator: VelvetGeorge

Post Reply
AndyK
Senior Member
Posts: 103
Joined: Thu Jul 25, 2013 3:37 pm
Just the numbers in order: 13492
Location: NJ

Incoming Marshall 74 JMP 50 - some questions...

Post by AndyK » Wed Jun 08, 2016 7:13 pm

Image
Image


Does anyone know what the two added tabs (one on the board, the other on the chassis) are for? Seems the power section was re-wired along with a new MM Power tranny. I'm not sure what the extra black and white wires are for either.

I plan on putting in an impedance selector, and a Marstran more correct transformer. But I am confused!

Andy
Top
User avatar
Carbia
Senior Member
Posts: 383
Joined: Sun Jul 05, 2009 1:34 pm
Just the numbers in order: 7
Location: Spain

Re: Incoming Marshall 74 JMP 50 - some questions...

Post by Carbia » Wed Jun 15, 2016 7:38 am

The tabs on the board puts the 220k in parallel with the bias resistor, to get bias range in the proper zone.

The tabs on the chassis are to feed the pilot light, probably coming from heaters.

Give it a chance to the MM power transformer. First, try the amp. If it sounds fine... why to change?
Top
Post Reply

Return to “Marshall Amplifiers”