TR11 B=0.7V, E=0V, C=0V ← that means MUTE is on … all outputs are shorted to GND.
Have to look at this circuit now (just above IC8) - the 4.2V = MUTE ON is the yellow line at the right - need to study how this works.
What are the voltages to the left of R50 and R59 and at Anode of D14?
Here is how it works:
Anode of D14 is at +5VD - if TR9 is closed then MUTE is at -12VA. If TR9 is open then MUTE is at +4.2V which is +5VD minus V D14 and a bit through TR9 ← that is what you are reading at TR11.
If TR9 is open then TR8 must be closed meaning that TR5 and TR7 must be open to cause that - hence must check what is at R50 and R59.
R50 goes here - ANMUTE (CPU-0) which to me reads as “Analogue Mute from CPU-0”
R59 same connector other side being MIDI Reset ?!?
Need to know these signals on R50 and R59 definitively.
Got a little more - that signal off R59 (RESET) comes from the DM board - maybe something stuck here due to the faulty 3.3V being 4.7V … maybe?!
