Have you checked the lithium cell 3V and the option programming? The display is ok? The ir sender use a pretty high voltage... 32V when i remember right... and the axial caps are pretty old. I found already some of them with a short, and a burnt resistor on the display. But it can also be dirt on the red plexy glas.

I replaced the 3V battery - didn't actually need to as it measured 3.1V after all these years still. Yes, I checked the option. The display is okay. I replaced on the front panel these capacitors - they all had very high ESR measurements C15 1uf/100V ESR 40.3 BAD C19 2.2uf/63V ESR 14.2 BAD C20 10uf/63V ESR 2.30 BAD After this, I checked that the amp was working but I did not check 2-way communication. I also replaced 2 capacitors on the CPU board - both of them gave no ESR whatsoever: C1 100 uf/10V - measured capacitance 14.7 - way out of spec C57 47uf/10V - measured capacitance 11.7 - way out of spec So, I presume that I may have done something wrong with one of these capacitors - or they need to be a certain brand. The two from the CPU board were the blue Philips type as well as two from the front panel.    

What remote are you using, and have you checked its two-way functionality with another Beomaster?

I have a Beolink 7000 and Beolink 5000. Both of them worked before I recapped the Beomaster. Highly unlikely that both of them would fail at the same time - especially since I repaired their 2-way communication module 1-2  years ago.