8525B/8528 Technical Service Manual Maintenance 6-13
Publication No: 15-02036 Issue 6
6.3.6 Replacement of Escutcheon or Switch Substrate
In replacing the switch substrate or the escutcheon on either the transceiver
or the control head the two parts can only be removed from the front panel
together and it is impracticable to separate them. It is therefore necessary to
have replacements for both parts (and the window fitted over the numeric
display behind the escutcheon) before the work is undertaken. Proceed as
follows:
1. Release the two screws at each side of the front panel and disconnect
the leads to the panel so that it can be removed completely from the
transceiver or control head. (Be careful to retain the screws for re-
assembly. Damage will result if they are replaced with longer screws.)
2. On the transceiver panel only: release the nut retaining the microphone
connector and withdraw the connector and loom through the front
panel.
3. On either transceiver or control head panels fitted with selective calling
switches: disconnect the switches from the Display PCB, then squeeze
the retaining fingers of the switch assembly while pressing the assembly
forward out of the panel.
4. Disconnect the switch substrate connections from the Display PCB.
5. Taking care not to scratch the paint, insert a screwdriver blade or
similar instrument under one of the left hand corners of the escutcheon
and switch substrate and raise the corner. Grip the raised corner and
peel off the escutcheon and substrate towards the right.
6. Withdraw the substrate connections through the slot at the right hand
edge of the panel.
7. Clean away as much sealant as possible from the slot in the right hand
side of the panel. (The slot must be at least clear enough for the
connections of the new substrate to be inserted clearly.)
8. Use a heat gun to soften the connections of the replacement substrate,
then form them to the required shape using the discarded substrate
connections as a pattern.
9. When the connections have cooled the substrate should be offered into
position to ensure that the correct settings have been made. If they are
not correct the connections can be reheated and reset.
10. When the substrate connections have been satisfactorily formed, peel
off the backing sheet from the substrate and position it on the front
panel. When it is correctly positioned, press firmly on its face to ensure
its adhesion to the panel.
11. Connect the switch substrate connections to the Display PCB
12. Test the switch operation as described in paragraph 6.2.3.
13. Refill the slot through which the connections pass with Expandite
Silicone Sealant 88 (Codan Pt No. 71-30000-007). Ensure that the slot
is completely sealed but that no excess sealant remains around the slot,
particularly on the front face.
14. Peel off the backing sheet surrounding the window opening in the
escutcheon and press the replacement window into place.
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