M3700 -32: all inputs disabled

[Ittol]

Hello everybody,
The automation of my 3700 was defective. On dynamic mode the audio signal was " chopped " on some channels.
And on snapshot mode, the fader's red and yellow leds were flickering on Null mode.
I found the 4 computer section cards ( same ref numbers) on Tascam Ninja website, and I started by replacing the MPU card, with no success. Then the AD card, and finally the two A and B channel switch cards.
At power on, the 32 bargraphs light normally.
All the mute led ( Eq, AUX, Monitor and Channel )light steadily when switched on.
I checked the connection of the 4 cards on the mother board and made several resets

But the 32 mic, line and tape are now disabled. No audio signal enters the console
The time code from my 2 MX2424 are no more displayed
I reverted to the 4 orignal cards : same result.
Have any idea?
Thanks for your help
Ittol

 

[Ittol]

Partly solved:
Any analog audio signal entering the console is directed to the A.D board.
I found that the A.D board was in short circuit. 2 slow blow fuses were blown in the main P.S.U.
The problem came from the mother board.
After replacement of the mother board, and with the spare A.D board fitted, every thing works well in the dynamic and snapshot automation modes, and the 32 inputs are enabled.
The 32 direct outputs , and the aux outputs are OK.
But a new problem appeared:
There is a loud 50Hz hum noise on the stereo and group outputs .
( Control room A and B, master tape, phones, studio out, and the 8 groups outputs).
The stereo master fader , and the group fader VCAs are connected to a control board, then the fader signal goes to the master control board and is then sendt to the balancing board.
I replaced that balancing board with no success.
There is no ground wire unplugged.
There is no apparent link with the 4 boards ( M.P.U, Channel switch A and B, and A.D) of the operation module, since the noise is still there when I disconnect the power supply of the operation module.