I have a 400 that I have rebuilt as full comp with the White Oak boards. When I purchased the amp it was not working and someone had attempted to do a repair on the LED boards and had lifted traces and otherwise made a mess of it. The amp is now working and sounds great but the LED boards are not functioning correctly based upon the behavior of my other 400 Series II. The channel B board, instead of showing a solid dot, displays three individual bars and the bars were in the middle of the display rather than in the left hand corner. The channel A board's display was a mess which I partially resolved by replacing a faulty transistor (thanks Joe). This resulted in it displaying in the same manner as the B board - better but not quite right.
I compared my boards to the boards pictured in the service manual and they are not the same. My boards only have two transistors, Q301 and Q302, and they are both TIS97. R304 is 10K on the B board and 1M on the A board. The leg of R306 that should be grounded per the schematic is not connected. Also, changing the value of R306 has no effect on the display.
I'm guessing that these are early model boards and without a schematic and/or a parts list I'm pretty much out of ideas. I'm hoping that someone is familiar with this iteration of the LED boards and can provide me with any information that they may have or tell me that the boards are working as designed (wouldn't that be grand).
Thanks!
I compared my boards to the boards pictured in the service manual and they are not the same. My boards only have two transistors, Q301 and Q302, and they are both TIS97. R304 is 10K on the B board and 1M on the A board. The leg of R306 that should be grounded per the schematic is not connected. Also, changing the value of R306 has no effect on the display.
I'm guessing that these are early model boards and without a schematic and/or a parts list I'm pretty much out of ideas. I'm hoping that someone is familiar with this iteration of the LED boards and can provide me with any information that they may have or tell me that the boards are working as designed (wouldn't that be grand).
Thanks!