A4 Ac Input Board; B1 Fan - Agilent Technologies 6571A Service Manual

Observe standard antistatic practices against ESD when working with the MOSFETs. Refer to Chapter 1
for more information on antistatic procedures.
1. Remove four screws securing the FET Board to the Heat Sink Assembly.
2. Remove the two screws securing each of the eight MOSFET's to the Heatsink Assembly and the sockets on the FET
Board. (Use a size T-10 TORX screwdriver to remove these screws. )
3. Unplug each MOSFET from the socket on the FET Board and separate the board from the Heat Sink Assembly.
Note
When you replace these MOSFETs (Q201-204, 211, 222, 233, 244), be sure to install the appropriate
mica insulator (see "Replaceable Parts") between each MOSFET and the heat sink.

A4 AC Input Board

1. Remove the A3 FET Board and Heatsink Subassembly as described in the combined procedure.
2. Disconnect the cable from A4J302.
3. Remove the 13 screws securing the AC Input Board to the chassis.
4.
Note
8 of these screws also fasten L400 and T300 to the board via standoffs between the board and the
chassis.
5. Slide board forward and remove it from chassis.

B1 Fan

1. Remove the fan cable from A4J302.
2. Remove the two screws securing the heatsink brackets to the fan bracket.
3. Remove the two screws securing the fan bracket to the bottom of the chassis.
4. Remove fan assembly (fan and bracket) from supply.
5. Remove the screws, washers, nuts securing the fan to the bracket and separate the two. (Use size T-10 TORX
screwdriver.)
74 Troubleshooting