What problem does it have?
Maybe you can repair it *without* schematic.
The biggest problem it has is that the first 7 pots sheared off the PCB. So what I really need is the pot values. If I had the values, I could probably go from there.
I'll be visiting a friend who is an authorized Marshall repair guy soon, and he'll probably be able to get it for me, but I wanted to see if anyone here had it available.
Just to save some time, or if you don't find it otherwise, you have different options:
Plan A): Maybe the values are silkscreened on the board (as in "A500K", not as "P1")
Plan B) Maybe the values are either stamped on the pot sides/back or printed on a small label pasted on the back or screened in tiny letters on the front side, on the phenolic strip itself (now hidden because they are sandwiched between the pot front and the front panel)
Plan C): unsolder the pots one by one (label them and the board with sharpie to remember position) and measure DC resistance between the outer legs, this will give you the value; setting the shaft to "5" , if you have approximately the same value center-left and center-right the pot is linear, if you find a great difference between both halves (almost 10:1), they are logarithmic.
Plan 9 from Outer Space: didn't you see it? It's been labelled the *worst* film in human history, quite an achievement. In fact it's quite fun to watch.
J.M., thanks for the suggestions, but the pots are all broken in half. The silkscreen on the PCB shows the reference designators, but no values. A couple of the pots were completely missing, with the others loose in the chassis.
I need to know what value of pot goes in each position. If I had enough clues to figure it out without a schematic, I would surely do so. The client would really like to have his amp back and I would like to have it off my shelf.
The only things that could help would be "plan s," for schematic, or "plan p" for parts list (with reference designators).
Would the G50 RCD be of any help?
Here is the G30 RCD parts list
(got it from Parts Is Parts web page)
Plan P! That might just do it! Thanks.
Funny thing about this series of amps is that although they seem very similar from the outside, the preamps are different enough that I couldn't make it out from any of the other MG amps.
Comment