Ricoh D131 Service Manual page 504

BCU/Finisher communication error: Timeout error
SC621-02 D
During communication between the finisher MBX and the BCU, no
ACK signal was detected for 100 ms, even after three attempts.
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BCU-PFB communication error
More than 2 in communication errors between the BCU and PFB
SC623 D
were detected after startup, or more than 3 errors were detected
after settings were initialized.
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BICU, LCT communication error: Break reception error
SC626-01 D
During communication with the LCT, the BICU received a break
(Low) signal.
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SM Appendix
Connection between main machine loose, broken, defective
Breaker switch defective
Power cord loose, broken, defective
Peripheral unit control board defective
BCU defective
Serial line level unstable, external noise on the line
Harness connectors between BCU and PFB loose, broken,
disconnected
Serial line connection unstable
External noise on the line
BCU defective
PFB defective
LCT connection to main machine loose, broken, defective
LCT control board defective
BCU defective
Serial line connection unstable
External noise on the line
2-37
SC600: Data Communication
D131/D132/D133