Keysight Technologies Infiniium MSOV 084A, Service Manual

Page: 69 / 164

Troubleshooting
4
Infiniium V-Series Oscilloscopes Service Guide 69
If no shorts are found on the bulk +12 V supply trace or if you have fixed all the
shorts and the oscilloscope still will not turn on, follow these steps, which include
replacing parts with known good parts until you discover the problem.
1
Replace the bulk +12 V power supply with a known good supply.
2
If the oscilloscope still does not power on, replace the motherboard with a
known good one.
3
If the oscilloscope still does not power on, then the backplane assembly is
causing the problem and must be replaced.
4
Once the faulty board or switch is discovered, be sure to reinstall all other parts
that were removed, as they were not the cause of the problem.
If the MAIN FAN FAIL LED is lit
If the MAIN FAN FAIL LED is lit, the problem is a cooling system failure.
Three fans are located on the left side of the oscilloscope to cool it. The circuitry
that generates the reference potential for the fans may have failed. This circuitry
failure would cause the fans to stop turning and the oscilloscope to shut down.
It is unlikely that all three case fans would become faulty simultaneously and stop
turning. It is more likely that the high side drive circuitry for the case fans failed.
Measuring the acquisition assembly resistance b12 V and ground