Fan Operation
4-50 72A-1230 Rev. F
July 22, 2005
M4100 Internal Checks
Certain internal checks can be performed quite easily, avoiding more
complicated measures. Many of these checks can be done with the M4100
unpowered. A few require that AC power be applied with the covers off.
DANGER If re-application of power is necessary to perform an internal check,
follow the procedural instructions carefully to minimize the risk of
electrical shock. In particular, make certain that only voltmeter probes
come in contact with internal test points. Furthermore, the High Voltage
Test Cable and Safety Switch extension must always be disconnected
from the Transformer case during internal measurement and inspection.
Fan Operation
With AC power applied, the fan typically does not run continuously.
Specifically, the fan is supposed to run only when the instrument’s internal
temperature exceeds 40 C, as measured by a thermostat located on the
Heater/Temperature Controller Board.
To check for proper fan operation depress and hold the push-button switch
labeled SW2, which is located along the top edge of the DSP/CPU Board
(Figure 4.36 on page 4-70). The fan should come on for a few seconds then go
off. If the fan fails to come on:
1. First try replacing the DSP/CPU Board by following the procedure in
”Replacing the DSP/CPU Board” on page 4-70, then retesting the fan.
2. If the fan still fails to come on when tested, replace the fan by following
the procedure in ”Replacing the Fan” on page 4-94.
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