I have seen a similar fault described on the forum somewhere but cant find the thread again - sorry.
I have a betapack 1 that has just developed a fault:
Channels 5 & 6 do not work - neither with control from a demux unit, or on manual overridde per channel. Simply no output.
The channel fuses for both channels are fine.
I have memories suggesting it is likely to be in the control circuitry somewhere as channels are controlled in 2s somewhere?? but would appreciate any further enlightenment.
The unit is 20 years old, and aside from fuse holders getting snapped, has had no issues to date, bless it.