Power Stages
The complete assembly of the two power stages and their heatsinks is attached to the chassis by
two screws accessible from underneath. Support the weight of the heatsinks while removing
them. It should then be possible to repair the assembly without detaching the power wiring from
the rear panel terminals. To detach a PCB and sense resistor assembly, remove the four screws
from the top terminals of the FET, the screw holding the thermistor to the heatsink and the screws
holding the sense resistor heatsink plate to the brackets. Retain these screws and washers for re-
use as their length is critical; screws supplied with a replacement FET may be too long.
If a FET needs to be replaced, note that a measured amount of high performance thermal
compound is used between it and the heatsink. Ordinary thermal grease is not adequate.
Before replacing the assembly, check carefully the condition of the low current wires to the main
PCB. Ensure that the grommets are correctly seated where the cables pass across the airflow
screen.
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