Workflow suggestions for refurbishing MC2125

[leshinb]

Hi Michael;

Thanks for the quick reply. The original board does not pass the signal past Q205 (the differential circuit). This started out with two shorted output transistors which also took out the 044-626. I got the output stage going
after an extensive search for output transistors. I ended up replacing all of the transistors past Q205. This is over a period of months when I can get to it. In the interim, I recently purchased a 045-144 board off of Ebay.
Basically, I got tired of hunting down and replacing components. Hopefully the purchased board will take care of it.

I finished my comparison of both boards, and yes, you are right, they are electrically compatible. I will have to move some wires. One is the input limit (violet wire) to the new pin 7. The other is the +Drive (orange) wire to
the new pin 19. Pin 7 gets moved to pin 8 on the new connector, and pin 8 gets moved to pin 9 on the new connector. I need to double check this but it looks like that should work.

I'll let you know how I make out. Thanks again for the information and quick reply.

Barry

 

[c_dk]

I think you are digging yourself a even deeper hole......using, modding at that, a board off the web of questionable origin vs. doing a correct and established repair.......

I am sure your driver board failed causing your output failure.......cenu07 and cenu57 predrivers are readily available and the subs for the to92 transistors have been published dozens of times here in AK forums.....

I would expect the differential pair to overheat and fail open as the distortion went beyond the expected norms.