Strange Marti M-30B

[mr_elbows]

Hello all;

I've uncovered an apparently 'factory-modded-hybrid' M-30B

I need some documentation for the following:

date codes on the filter caps and toroidal transformer indicate a build date
of 11-73

with the top cover off, there is a 4-3/4 x 7-1/4 metal plate mounted at the
left front corner of the chassis.......long dimension goes front-to-back

on the plate, L to R are:

CA-40
MA-3
LA-12

there's also another board, about 2 x 4, underneath, to rear of the 6BL8
socket, with several caps, resistors, one transistor, a variable inductor,
and two potentiomenters on it..........which seem to be 1) deviation and 2)
'adjust-for-least-distortion' ala the pots in a DFM-1D module

I'm wondering if this is a return-to-factory retro-fit, but the underside
wiring looks to be 'all original', not as if someone stripped out the
12AX7-6BL8-6CG7 prior to fitting the plate and re-wiring it

pictures if you need 'em, let me know

Gary

 

[TomT]

Sounds like a very well done field modification. My memory, fading though it may be, is that the solid state 40 watt Marti units were in production before 1973, probably late 60's. One place I worked had a M-30 that was new in 1964, so that kind of brackets the models