Sony PVM 2950Q randomly switches inputs / need new chassis

[zeno]

Try removing the TAC switches one at a time & see what happens.
With old age many go leaky. Finding a new MPU would be a real stroke
of luck & may not be the problem. Many TV micros are the same BUT
they are burned in different. Example is Toshiba TNP-####-####
the last four numbers must match or it may not work or not work right.
The IC's themself started life all the same but got burned in with instructions.

good luck
73 Zeno
LFOD !