Appendix 1 Protection Of Ics In Data Output Circuit - Furuno Satellite Compass SC-50/110 Service Manual

Appendix 1 Protection of ICs in Data Output Circuit

Appendix 1 describes how to prevent ICs in the data output circuit temporarily.
Refer to Appendix 2 for permanent remedy.
Symptom
U1, U2, and U3 in the heading output circuit are damaged.
Cause
Ground potential difference - The cable shield, or a signal return path between
the circuit grounds of the equipment is not connected securely. The shield is
connected to the unit through the cable clamp on SC-50/110, while the
connector pin is used on SC-60/120.
Remedy
At installation: Carry out 1) to 4).
When the symptom occurs: Carry out 1) to 5).
1) Solder a grounding cable to the cable shield and ground it through the
screw fixing the MAIN board. See the attached sheet.
2) Ground SC-50/110 processor unit securely.
3) Connect the cable shield at the end of the interconnected unit as below.
IEC61162-1 and AD-10 (photo coupler): Frame Ground (FG)
IEC61162-2 (RS422/485): Signal Ground (SG)
4) Connect the interconnected unit securely
5) Add zener diodes in the heading output circuit to protect the
IC from being damaged by surge.
Factory-modified sets
SC-110 (SC1101): 4404-0329 and after
SC-50 (SC501): 4403-2224 and after
Fig.1 Zener diodes added in data output circuit
15
J2 to J7
Zener diodes added
Type: RD9.1EB3-T4
C/N: 000-138-700