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Removing the Voltage
Selector/Fuse Holder
Assembly
Replacing the Series
Pass Transistor
TM 502A Instruction Manual
2. On the power supply assembly, remove the screws on each side that
secure the series-pass transistor clamp; remove the clamp .
3. Remove the four screws on the interface connector side of the power
supply assembly that secure the circuit board to the chassis.
4. Disconnect the two connectors going to the transformer from the circuit
board .
5. Slide the circuit board out of the power supply assembly .
Use the following procedure to remove the voltage selector/fuse holder
assembly.
1. Remove the cabinet and the circuit board. Refer to
Removing the Cabi-
net
and Removing the Circuit Board earlier in this section .
2. Disconnect the connectors from the terminals on the back of the voltage
selector/fuse holder assembly and label each wire .
Do not apply excessive force to the locking tabs. Excessive pres-
sure will break or reduce the strength of the plastic .
3. The assembly has a locking tab on two sides that secure it in the chas-
sis hole. Push one tab in carefully, pulling gently on the assembly from
the outside, until the side releases.
4. Repeat the previous step to release the other side .
5. Pull the assembly through the chassis hole to the outside while taking
care not to damage the capacitors .
Use the following procedure to replace the series pass transistor.
NOTE
You must apply a new adhesive insulator plate to the transistor
before installing it. Do not use the insulating plate from the old
transistor to maintain the proper insulating characteristics .
1 . If you have not already done so, remove the cabinet and the circuit
board as described earlier in this section.
2. Unsolder and remove the transistor from the circuit board .
3-5
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