GAI-Tronics 12504-010 Keypad Replacement Kit for 491-201 Mine Dial Page Telephone - Manual (Page 3)

Pub. 42003-218B
Model 12504-010 Keypad Replacement Kit for Model 491-204 Mine Dial Page Phone Page: 3 of 5
f:\standard ioms - current release\42003 kit manuals\42003-218b.doc
07/09
Procedure
1. DISCONNECT the Mine Dial Page Phone telephone line’s connection from the communication
system.
2. Open the enclosure and disconnect both wires from the positive terminal of the battery.
3. Take note of the positioning of the tie-wraps securing the keypad and wires of the 69491-002 PCB
assemblies. Wires MUST be routed and secured to prevent contact with uninsulated conductors.
Securing of the wiring in the same fashion will be required at completion.
4. Cut each tie-wrap that is holding the keypad wires and the 69491-002 wires to the enclosure wiring
harness. Using the Phillips screwdriver, loosen all screws to remove the keypad wires from the
terminal block TB2 and terminal E1 on the 69491-002. Re-tighten all loosened screws to ensure that
all other wires remain connected to their appropriate locations. See Figure 5.
Figure 5.
69491-002 Modification for Maintaining Intrinsic Safety
(Used in conjunction with keypad PCBA modification)
5. Remove the two 4-40 screws securing the 69491-002 PCBA. Save for re-assembly.
6. On the 69491-002 PCBA, locate R104, which is adjacent to C101 and E2. Refer to Figure 3.
7. De-solder and remove R104 (100-ohm resistor, ½-watt).
8. Install new R104 (100-ohm resistor, 3-watt). Re-solder and trim leads.
9. Re-coat the PCBA around R104’s soldered connections with an approved moisture resistant material.
10. Swing the PCBA out of the way for access to the keypad assembly.