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Marshall 3210 repair

Started by tette2, December 19, 2023, 04:30:53 PM

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tette2

Hallo !   This is my first post since some years .  I´m trying to repair a mosfet amp  from Marshall.  It might be that the factory have mounted a transistor Tr2 ,  BC 184 a half turn wrong ! ?   In the amp there is anorther BC 184 but this one seems to be mounted correct . The same with all the other NPN transistors in this unit.  There is some pictures in the Marshall forum that shows TR2 and how it is mounted .  Wrong as I can understand.
A question I have is if You think I should replace all the 15 small electrolythics ?  The two large 2200 uF/50 V  is already replaced by some tech.  I also have some scratchy pots. The treble pot didn´t improved in spite of de oxit spray.   Thanks for some advice .
With a signal into the returnjack the poweramp sounds clean and nice so there is some in the preamp.... some strange , distorted sound .  Can that problem disappear with new , small ecaps ?

g1

Do you have the proper footswitch?  Without it, these amps don't really work right, you get a mix of clean and dirty channels.
TR2 determines what the eq is doing, depending on which channel is selected by the footswitch.  It may be fine, you can look at the pinout for BC184 and see if the correct leads are going to the correct places (emitter to ground, collector to VR6).
Small value caps that are in the signal path are prone to degradation and cheap, so you might just want to replace them.  Or check them with a dedicated cap tester.

Tassieviking

Don't know if it helps but here is a photo of a 3210 PCB I found on the net some time in the past,and schematics 2 & 7.
There are no stupid questions.
There are only stupid mistakes.