FCO 85XBA-R005 Rev C, Shuts down prematurely because of temp sensor

This Field Change Order (FCO 85XBA-R005, Revision C) outlines a retrofit procedure for all VAX 85X0 systems, upgrading them to Revision Level "D1". The FCO addresses a critical issue where the machine prematurely shuts down due to an error in Temp Sensor-3.

The solution involves swapping the locations of Temp Sensor-3 and Air Flow Sensor-1, which also requires the installation of an adapter plate (P/N 74-35168) and new labels from the EQ-01470-01 kit. The procedure, estimated to take one hour, details steps for system shutdown, power-off, opening the CPU cabinet, removing and replacing specific components (like the Power Bus Bar and Air Exhaust Vent), carefully routing sensor cables (using tie-wraps to prevent chafing), applying new labels, restoring power, updating system parameters in PL2REG.DAT, running micro diagnostics, and bringing the operating system back online. The document also notes that some temperature sensors manufactured with specific date codes (709, 710, 715) may have an early failure rate within the first 75-100 hours of operation, providing a replacement part number (P/N 12-22805-00) if necessary. Required tools include a Field Service Tool Kit, VELOSTAT Electrostatic Field Service Kit, and a torque wrench.