Connect your digital multimeter to the test points designated TP1 and TP2 on the main board.
Focus airflow on the primary transformer, power transistor heatsinks, and main circuit board.
| Original Part | Type | Modern Substitute | Notes | | :--- | :--- | :--- | :--- | | 2SC5200 (NPN pass) | Power transistor | MJL4281A | Higher SOA, identical pinout | | 1N4148 | Signal diode | 1N4148 (still made) | No change | | 4700µF/50V (85°C) | Electrolytic cap | 5600µF/63V (105°C) | Improved ripple rating | | LM723 | Voltage regulator | UA723 or direct drop-in | Still in production | | 5k pot (voltage adjust) | Carbon potentiometer | Bourns 91A1A-B28-B15L | Sealed, longer life |
Tighten all screw terminal wire connections to the specified torque value of 1.2 Nm. ps-855b maintenance manual
When the PS-855B encounters an operational fault, use this matrix to quickly isolate and resolve the issue. Symptom / Error Code Potential Root Cause Recommended Action
Wipe down the outer chassis with a dry, lint-free microfiber cloth. Monthly Maintenance
Disconnect all primary power sources before removing any protective chassis covers. Ensure the power isolation switch is locked and tagged. Connect your digital multimeter to the test points
: Required intervals to ensure continued airworthiness, similar to a preflight inspection.
When the PS-855B experiences an operational fault, use this matrix to quickly isolate the root cause and apply the correct remedy. Fault Code Matrix Error Indicator / Code Possible Root Cause Recommended Corrective Action (Overheating) Blocked air intake or failed cooling fan.
Clean the adjustment potentiometer with electrical contact cleaner. Over-temperature fault When the PS-855B encounters an operational fault, use
While the full manual contains many detailed procedures, here are the core maintenance areas it covers.
Ensure ambient temperatures and ventilation clearance around the unit meet factory specifications. Monthly Maintenance Tasks
Main fuse blown or tripped breaker; loose input power wiring.
Check all external data and power cables for fraying, pinching, or insulation degradation.
For deeper diagnostics, the L3Harris PS-855B maintenance manual may reference the "ShockBox BFG Capacitance Test Box" (Part #: SB24-03-835). This manually operated test unit is designed specifically for the PS-835, PS-850, and PS-855 series. It allows a technician to apply a precise load to the battery and verify its capacity against the parameters in the manual.