Locate the primary fuse holder, typically situated near the main power input module.
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The is an Emergency Power Supply (EPS) manufactured by L3Harris (formerly JET/L-3 Communications) that provides backup power to attitude gyros and other critical avionics during a total aircraft power failure. Maintenance for this unit is primarily governed by the Component Maintenance Manual (CMM) TP-483 , which includes an Illustrated Parts List (IPL) . Primary Maintenance Manual: TP-483
Use a calibrated digital multimeter (DMM) to verify zero voltage at the input terminals. ps-855b maintenance manual
Let’s walk through a real-world procedure as documented in the .
Focus airflow on the primary transformer, power transistor heatsinks, and main circuit board.
When storing, the battery should be in a cool, dry place and recharged periodically to maintain capacity. 4. Troubleshooting and Repairs Locate the primary fuse holder, typically situated near
: According to L3 Service Letter SL-170 , the battery condition must be checked every 3 to 6 months .
: Revision B (dated July 30, 2014) is a widely cited version. ATA Chapter : Typically found under ATA 24-30-08 .
Wipe down the outer chassis with a dry, lint-free microfiber cloth. Monthly Maintenance Maintenance for this unit is primarily governed by
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The L3Harris PS-855B is an designed primarily for the aviation industry. Its primary function is to act as a last line of defense in the cockpit, providing critical power to self-contained attitude gyros and other emergency equipment in the event of a total aircraft power failure. The PS-855B is the heart of an aircraft's emergency bus, ensuring that pilots retain essential flight instruments and systems when every second counts.
The manual’s parts list specifies or low-ESR capacitors (e.g., Rubycon ZLH, Nichicon HE). Using general-purpose caps leads to overheating and short life.
Check that air intake and exhaust vents are free of dust accumulation. Quarterly Maintenance
Ensure ambient temperatures and ventilation clearance around the unit meet factory specifications. Monthly Maintenance Tasks