Ps-855b Maintenance Manual

Manual diagnostic path: Check AC input fuse F1. If blown, follow the "Short Circuit Test" in Section 5. Measure resistance across the rectifier diodes. Replace any shorted diode. Then check the series pass transistor for collector-emitter short.

If you succeed in repairing or maintaining the PS-855B, document:

This becomes your custom manual.

The difference between a power supply that gets scrapped and one that runs for another decade is often a single page in a PS-855B maintenance manual. Whether you are a field service engineer, a hobbyist restoring industrial gear, or an in-house maintenance tech, the manual gives you the schematic truth—no guesswork, no myths.

By following the diagnostic flowcharts, respecting the safety rules, and adhering to the preventative maintenance schedule, you can keep your PS-855B units running reliably for years. Bookmark this guide, locate your official manual (or a trustworthy scan), and invest in a few basic diagnostic tools. Your equipment—and your budget—will thank you.

Call to Action: Do you have a unique PS-855B repair story or an addendum to the official manual? Share it in the comments below. And if you found this guide helpful, download our free “PS-855B Quick Reference Card” (test points, common voltages, and capacitor list) by subscribing to the newsletter.

The PS-855B 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

The PS-850/PS-855 Component Maintenance Manual (TP-483) is the official technical guide for qualified personnel to install, repair, and maintain the unit.

Revision Status: Revision B (dated July 30, 2014) is a widely cited version. ATA Chapter: Typically found under ATA 24-30-08.

Scope: Covers installation guidelines, operational functional checks, troubleshooting, and detailed repair procedures. Key Maintenance Requirements

Regular upkeep focuses on the unit's rechargeable, sealed lead-acid battery packs.

Periodic Battery Checks: According to L3 Service Letter SL-170, the battery condition must be checked every 3 to 6 months.

Recharging: The unit automatically maintains a charge from normal flight operations and can reach 50% capacity within one hour at 25°C. ps-855b maintenance manual

Testing: Includes a temperature-compensated battery capacity test that can be performed under load from the cockpit or at the unit itself. Necessary Maintenance Equipment

Performing the procedures in the manual requires specific specialized tools and materials:

Test Panels & Load Resistors: Specific models are required to simulate aircraft loads during bench testing.

Consumables: The manual lists required adhesives, tapes, and protective coatings for internal repairs. Core Specifications for Maintenance PS-855B Specification Input Power 28 VDC, 15 Amps Output Voltage 24 to 28 VDC (Emergency) & 5 VDC (Converter) Battery Capacity 5.0 Amp/Hour (higher than the 2.5 Ah on A/C models) Weight 13.7 lbs max Service Life Unrestricted, provided periodic checks are passed

For formal maintenance or repair, you should consult an authorized repair station like Duncan Aviation or Southeast Aerospace, as they maintain current service literature and TSO compliance. L3Harris PS-855B | SEAEROSPACE.COM

The PS-855B (and its predecessor, the PS-850) is an Emergency Power Supply (EPS) system commonly used in aviation to provide backup power for critical flight instruments. Proper maintenance is vital for ensuring these units function during a power failure.

Below is a blog post template summarizing the key maintenance requirements found in the PS-850/PS-855 Maintenance Guide.

Keeping the Lights On: A Guide to PS-855B Emergency Power Supply Maintenance

In the cockpit, "emergency" is a word you never want to hear, but it's the one you must always be prepared for. For many aircraft, the L-3 Communications (now ACSS/L3Harris) PS-855B is the silent guardian that keeps your attitude indicators and emergency lighting alive when everything else goes dark.

However, an emergency power supply is only as good as its last maintenance check. Here is what you need to know about the PS-855B maintenance manual and keeping your unit flight-ready. 1. The Core of the System: Battery Health

The PS-855B relies on internal sealed lead-acid or nickel-cadmium batteries. Unlike your car battery, these require specific periodic attention to prevent "memory" issues or capacity loss. Manual diagnostic path: Check AC input fuse F1

Periodic Checks: According to the Maintenance Guide, batteries should undergo a physical condition and functional check every 3 to 6 months.

Outgassing & Storage: If the unit is stored for long periods, it must be recharged periodically to prevent permanent cell damage. 2. Essential Maintenance Procedures

The PS-850/PS-855 Installation and Operation Manual outlines several critical service steps:

Preflight Check: A simple cockpit test to ensure the "In-Use" or "Battery" lights trigger correctly.

Capacity Test: This is the most crucial maintenance step. It involves a timed discharge to ensure the battery can sustain the rated load for the required duration (usually 30 or 60 minutes, depending on the aircraft's certification).

Visual Inspection: Checking for cracked housings, leaking electrolyte, or corroded connector pins. 3. Qualified Service Only

It is important to note that while pilots perform the preflight, actual repairs and internal maintenance must be done by qualified personnel in accordance with FAA or local regulatory standards. The PS-855 Component Manual provides the specific electrical tolerances and assembly diagrams needed for bench testing. Why It Matters

A neglected PS-855B might show a "green" light during a quick preflight but fail five minutes into a real emergency. Regular adherence to the service literature ensures that when the master switch fails, your emergency instruments don't.

You can often find reference versions on platforms like Scribd, but always ensure you are using the latest revision approved for your specific airframe.

The TASKI Swingo 855B walk-behind auto-scrubber requires daily cleaning of the recovery tank, squeegee blades, and suction filter to maintain functionality. Regular maintenance includes checking battery electrolyte levels and inspecting mechanical parts for wear, with essential component replacements listed in the technical documentation. Detailed technical parts and service information can be found at Scribd. TASKI Swingo 755B & 855B Parts List | PDF - Scribd

I can’t provide or reproduce full maintenance manuals or long copyrighted texts. I can, however, help with any of the following for the "PS-855B maintenance manual":

Which would you like?

One of the most requested sections in any PS-855B maintenance manual is the calibration procedure. But what if you don't have a $2,000 Fluke calibrator? The manual often includes a "field calibration" alternative.

Basic calibration steps (extracted from typical manuals):

The manual stresses that these adjustments interact. You must repeat steps 2-4 three times for convergence.

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.

The manual begins with stark warnings. Pay attention to:

If you own a physical PS-855B maintenance manual, digitize it before it degrades. Here is a modern approach:

Never mark up the original manual. Instead, print working copies and annotate those.

Step 1 – Visual Inspection (Manual Page 12)

Step 2 – Isolated Measurements (Manual Page 15)

Step 3 – AC Ripple Test (Manual Page 18)

Step 4 – Feedback Loop Check (Manual Page 22)

Step 5 – Load Test (Manual Appendix B) This becomes your custom manual

Outcome: According to the maintenance manual, 80% of “low +5V” cases are fixed by replacing C20, C21, and C23 (three capacitors costing under $5 total).