I have a 1971 (yes its stamped on the chassis) Concert Bass amp and I need a proper schematic for it. The circuit diagram on this site is a later version and I have found many differences on my power board (i.e. no trim pot for the first drive stage, several variations on resistors in the various power supplies, etc).
I have a problem with the +25V supply on my amplifier. The unloaded DC voltage is 49V and I can not find the problem on either the pre-amp or power amp boards (open circuit??). My last effort will be to check all the FETs and BJTs on the preamp board.
THX
