Specifications

Chapter 4: Troubleshooting
Power Supply Troubleshooting
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Figure 4-13 Measuring the backplane assembly resistance between +12V and ground across Q1409.
If the MAIN FAN FAIL LED is Lit
If the MAIN FAN FAIL LED is lit, the problem is a cooling system failure.
Four fans are located on the left side of the oscilloscope to cool it. It is possible that
the circuitry that generates the reference potential for the fans has failed. This circuitry
failure would cause the fans to stop turning and the oscilloscope to shut down.
It is unlikely that all four case fans would become faulty simultaneously and stop
turning. It is more likely that the high side drive circuitry for the case fans failed.
Follow these steps to diagnose a main fan failure:
1 Reset the sensing and shutdown logic by removing the AC power until the green LED
on the motherboard goes out (or just wait 30 seconds).
2 Move around to the left side of the oscilloscope so you can see the case fans (Figure 4- 14).