RC25 and RC36 Rate Compass

Compass is causing communication failure
We have during the past few months seen an increasing number of RC25 and RC36 rate compasses being returned with a common failure.

Symptom
The autopilot displays “Com. Failure with J3XX” or “Com. Failure with ACXX” depending on the autopilot model.

Cause
A defective IC100 (RS485 Bus Driver) in the compass short circuits the Robnet bus and activates the communication failure alarm.

Remedy
Simrad have made a new PCB layout for these compasses with improved protection of IC100.
The protection consists of four transorb diodes on the Robnet and Robnet2 buses. These new diodes are D100, D101, D102 and D103.
The new PCBs have got revision code DA, and are already taken into use in the compasses.
There is no new product code on the compasses, but we have following references in serial no’s:
RC25: from s.n. 4675
RC36: from s.n. 4023
Please observe that it is not possible to modify units that have earlier revisions of the PCB. A replacement PCB is the only cure.

Obvoisely arrangements need to be made if you encounter this problem. Please contact me accordingly.

Regards Frank.