Ergomo B/B PCB repair

[Mr H]

My Ergomo has failed. There are no Watts or Cadence readings on the
display. In the service menu there are no square waves when the crank
is rotated. I have removed the silicone protective layer from the
Printed circuit boards and probed the opto coupler outputs but the
outputs aren't turning on as the axle is rotated. I have checked the
wiring back to the connector. Power is being supplied to the PCB. HR,
altitude and Speed outputs are still working.

I wonder if anyone has attempted to clean/repair the opto couplers and
if so how are the PCBs removed without damage? Are they bonded to the
casing? If the PCBs cannot be removed without damage, can new PCBs be
obtained?

Dave.