Motorola CDM1250, Basic Service Manual

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2-6 Maintenance
3. Slowly lift the transceiver board on the edge at the front of the radio (the edge that mates with the
control head) and pull gently toward the front of the radio as shown in Figure 2-5. Take care to
slide the antenna connector and power connector out of the chassis towards the front.
Figure 2-5: Transceiver Board Removal
2.6.3.1 LowBand Transceiver Board Removal
1. Remove the Control Head and Top Cover as directed in Sections 2.6.1 and 2.6.2 of this Manual.
2. Using the T20 TORX™ driver, remove the nine screws holding the die cast cover to the radio
chassis.
3. Remove the 20-pin accessory connector from the rear of the radio by pulling on it away from the
radio chassis with one hand while holding the radio chassis with the other.
4. Remove the plastic protective cover over the opening at the front of the radio chassis that allows
access to the 18-pin flex connector.
5. With the chassis sitting on the tabletop, insert one side of the dismantling tool, 6686119B01, into
the bottom of the opening at the front of the radio chassis. With the tool inserted between the bot-
tom of the 18-pin flex connector and the radio chassis, use it to gently pry the transceiver board
up from the radio chassis. The transceiver board may stick to the radio chassis as a result of the
thermal material that is used between the heat dissipating devices and the radio chassis. Con-
tinue applying an up and down force to the transceiver board until the various components
become unstuck, and the transceiver board becomes loose enough to remove from the radio
chassis.
6. Once the transceiver board is removed from the radio chassis, handle it per the procedure for
“Safe Handling of CMOS and LDMOS Devices”, Section 2.3. In addition, take care not to disturb
the thermal pad material that may adhere to the devices that mate with the thermal pads located
on the radio chassis. Do not disturb the thermal pad on the radio chassis as well. Also, do not dis-
rupt the conductive bead gasket that is applied to the radio chassis walls.
2.6.3.2. Removing and Replacing Defective LDMOS Devices (Q1402 and Q1403)
1. Note that if one of the two Final stage devices (Q1402 or Q1403) is defective (i.e., TP1402 or
TP1403 resistance to ground is less than 25 kOhms), replace both devices, since the other
Note: If removing the transceiver board from the radio chassis causes the traces of the
board to lift up away from the board, most noticeably around the final devices
(Q1402, Q1403), the transceiver board must be scrapped and a new replacement
transceiver board is required.
Lift
Antenna
Connector