Product Repair Instructions for the MPS-24 / AVPS-24 Power Supplies

Use the following instructions for repair of MPS-24 or AVPS-24 power supplies that may have a defective PTC component.

Problem Identification

Systems which may exhibit this problem include AM-2020, AFP-1010, XP, System 5000, System 2500, Sensiscan 2000, or System 500 models which were shipped from Notifier/Fire-Lite between May, 1991 and January 15, 1992. Only those systems which use the MPS-24, MPS-24E, MPS-24F, AVPS-24, AVPS-24E or AVPS-24F modules may have the problem. MPS-24A or MPS-24B series power supplies are not affected.

The defective part is a particular PTC (Positive Temperature Coefficient) resistor used for power limiting, acting as a self-restoring fuse. It limits power for unregulated DC indicating appliances. Although rated for 3.75 amperes, the component may activate after 2 to 10 minutes if the load current exceeds 2.0 amperes, causing a shutdown of any indicating appliances or other output devices connected to the system. This component is a yellow disk, marked “E7500 3.75A”, located on the power supplies as shown below. On the enclosed replacement board, the non-defective part is marked with the same number, but is noticeably thicker.

Diagrams of Power Supplies

MPS-24 Power Supply: This diagram shows the MPS-24 circuit board. It highlights a 'Defective component' indicated by an arrow pointing to a specific location on the board. Another label points to 'Mounting screws' with arrows indicating their locations. The board features various electronic components, connectors, and a heatsink.

AVPS-24 Power Supply: This diagram shows the AVPS-24 circuit board. Similar to the MPS-24, it indicates a 'Defective component' with an arrow and points out 'Mounting screws' with arrows. This board also contains numerous electronic components and connectors.

Repair Procedure

1. Notify the local fire department, building owner, and other local authorities of the plan to temporarily disconnect the fire alarm system for service.
2. Shut off main AC power to the system.
3. Disconnect all batteries connected to the MPS-24 or AVPS-24 power supplies.
4. Remove all wires and cables connected to the PC board on the MPS-24 or AVPS-24 power supplies. If necessary, mark the wires to aid re-installation.
5. Remove 7 screws from the MPS-24 or 4 screws from the AVPS-24 as shown above. Set the screws aside for later re-installation.
6. Remove the PC board and replace with the board supplied by this kit. Install the screws.
7. Connect all wires and cables in their original position on the PC board. Do not yet connect the batteries.
8. Apply AC power to the system.
9. Connect the batteries.
10. Test the system, especially the power supply outputs.
11. Notify all authorities that the fire alarm system is again operational.
12. Package the board with the defective PTC in the carton used with this kit.

Return Information

Return to:

Notifier/Fire-Lite Alarms
Repair Department
12 Clintonville Rd.
Northford, CT 06472

Document #15098-A 2/4/92

Source: www.PDF-Zoo.com, firealarmresources.com