Hi Carl,
I’m probably not going to help you but you may have helped me!
I have had a similar problem with my Beolab 3000s, detailed here:
Beolab 3000s switching on and off in use
Without any solution really. However your post has encouraged me to try something new, which is connecting via a not-fully-wired Mk3(?) powerlink cable. In fact BM6500 > PL3 > BL4000 > PL2 > BL3000, as the only PL3 cable I have is fairly permanently routed. Anyway, todays experiments are:
BM6500 > PL2 > BL3000: rapid switching on and off started after about 30 minutes, and whether the display is turned on or off (Audio/Video/Standby switch)
BM6500 > PL3 > BL4000 > PL2 > BL3000: currently been on for about four hours without switching off, which is the longest I’ve managed in a long time. No signal going to the displays obviously with the PL3 cable.
So I think my BL3000 problems might be the same as yours, i.e. related to the display. My displays work fine until the switching starts, but then turn off until I give them a new input, e.g. change the volume. Do yours do the same?
I’ll do some more experiments nest weekend, including trying the other BL3000. I could live without the displays if the speakers work with powerlink, but I’d rather have the displays too!
Dave