Yes I think we should ignore the transceiver numbers from now on! Mine are all 2046 or 2047, but all show SW2.0 so let’s suppose they all work the same with MCL2AV (except 2045).
Ok, tried this now with both of the IR eye’s and the MCL2AV being stand alone or connected to the 1611 and the BC6. No way in any case will it respond to the timer + reset command or timer + AV for that matter. so no wiser on this matter. Of course my MCL2AV arrived with defects, so it might as well have other defects.
I just tried removing the transceiver grey and/or yellow connectors to my MCL2av to see if I could replicate your mute fault. It works fully with grey and/or yellow disconnected – I just lose the ability to store start up volume (and it starts quietly each time). With those wires disconnected there is continuity between the grey and yellow terminals as shown on the circuit diagram.
Given that your other MCL2AV fault was a 5v supply problem, and the muting circuit seems to use a 5v supply, perhaps whatever damaged TR13 also damaged TR100? Perhaps someone connected an incorrect power supply (or incorrect polarity) in the past.