Marshall YJM100 schematic?
I am repairing a Marshall YJM that has a faulty Hi channel I input. This is the input that is routed through a switchable boost (probably a DOD 250 circuit). This Hi input is very dull while the low input of this channel is bright as it should be. As a consequence, the issue is probably located on the "boosst" board which is all CMS. the switching is done through a relay which seems to be fine. Also, i can test continuity from the input jack (jack inserted) throught to the first grid 68k resistor located at the side of valve 1. Sale for the ground connection: no problem here. The input impedance seems to be fine as well (the dullness doesn't seem due to a drop in input impedance as it is higher than 1MOhm).
If anyone has the schematic, it would be of great help!
Thanks in advance!
confirm which chip you replaced.
So all you done was replace the RC4558 SMD, and it was fixed?
Originally Posted by Nyqusit5
This is the SMD RC4558 directly on the other side of the boost dials on the rear board eh? at the far left side of the rear circuit board just under where the 2 plug sockets are eh?