This product bulletin is to inform customers of a potential COM4 board compatibility issue with Comet Electronics RailNet APU Pentium version 5 upgrade. It applies to 486-based APU units that have been upgraded with the APU Version 5 Pentium Kit. This applies only to units containing either a COM4 board or a COM4A board manufactured before 1999.

Specifics

Compatibility testing has revealed that in rare instances, when a 486-based APU is upgraded with the APU Version 5 Pentium Kit, there may be a conflict with the existing quad-channel UART on the COM4, or COM4A board that was manufactured before 1999. The issue is manifested as communications difficulty and may affect any of the ports on the COM4(A), e.g., AI1200, ITC, REDI, etc.

COM4(A) boards manufactured after 1999 have not exhibited this issue.

The issue may be remedied by replacement of the incompatible UART chip on the COM4(A) card or replacement of the COM4(A) card entirely.

Inspection and Replacement Procedure

WARNING!

Observe proper ESD procedures when performing these procedures.

COM4(A) Card Replacement

1) Power off the APU and remove the COM4(A) card.

2) Examine the UART chip, U11, on the COM4(A) board. If the chip is manufactured by any manufacturer other than Texas Instruments, the card needs to be replaced with one with an acceptable spare with the TI UART chip installed. Follow standard RMA procedures to have the suspect board repaired.

Board Identification


Figure 1: COM4 board (older version) with non-TI UART chip	Figure 2: COM4A (current version of board) with non-TI UART chip

UART Chip Replacement

Field replacement of the UART computer chip should be done ONLY by qualified technicians. Most readily available PLCC chip extractors (or other methods) can damage the chip or socket if not used properly. If the socket is damaged, the board must be returned to Comet Electronics for repair following our standard RMA procedures. Our flat rate repair charges will apply for damaged boards. If the pins of the replacement chip are damaged, it must be replaced.

Refer to Field Procedure 376-0018-00 for the specific replacement procedure.

Important!

DO NOT perform this rework on the COM4 from an operating site. If the COM4 from an operating site is damaged, the site will be out of service until a spare can be obtained. Perform the rework on a spare or replacement board only.