Chapter 5 123
Troubleshooting the Synthesizer Section
Verifying the A9 2nd LO/ Fan Control Board
Verifying the A9 2nd LO/ Fan Control Board
If the Fans Are Not Operating
CAUTION The power supply may be in thermal shutdown if the instrument has
been operating without the fans running. Allow the instrument to cool
down before troubleshooting.
If all three fans are not operating, suspect a power supply problem or a
defective fan control circuit on the A9 2nd LO/Fan Control assembly.
Refer to “A5 Power Supply Assembly Description” on page 153 to check
the individual supplies. If the supplies are within specifications, the
most probable cause is a defective A9 board. Refer to Chapter 11 for
assembly replacement procedures.
If only one or two fans are not functioning, and the power supplies are
within specifications, suspect the A9 assembly or a defective fan.
1. Remove the front frame from the instrument. Refer to Chapter 11 for
removal procedures.
2. Refer to Figure 5-2. Measure all of the fan voltages at J3, J4, and J5
on the motherboard.
Figure 5-2 Fan Voltages
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