Ps-855b Maintenance Manual -

PS-855B Maintenance Manual

1. Critical note from the manual:

   The PS-855B uses a thermal compound between the pass transistors and the heatsink. This compound dries out after 7-10 years. The manual specifies that during any major service, you must remove old compound and apply fresh silicone-based thermal paste to prevent thermal runaway.

   • Use a resistive load bank. The manual specifies 80% load for 30 minutes.

   The maintenance manual includes a matrix of common faults, probable causes, and remedies. Key entries include: ps-855b maintenance manual

   Fault Isolation

   : Steps to identify failures in the internal charging circuit, battery packs, or 5 VDC converter. Critical note from the manual: The PS-855B uses

   Emergency Power Supply (EPS) unit manufactured by (formerly J.E.T. / BFGoodrich) and now supported by Extant Aerospace Use a resistive load bank

   • MOSFETs (gate threshold, body diode)
   • Optocouplers (CTR)
   • Transformers (inductance, turns ratio)

   Physical copies of vintage maintenance manuals frequently surface on eBay. Search for "PS-855B service manual original." The benefit of a physical manual is the large fold-out schematics.