Keysight N9038A MXE Service Guide 375
Power Supply & Midplane
A7 Midplane Board Assembly Troubleshooting
A7 Midplane Board Assembly Troubleshooting
The A7 Midplane board assembly is serviced as an assembly only; no
component level repair is supported.
Instrument Power Supply LEDs and Test Points
While the A6 Power Supply assembly has no user accessible LEDs or test
points the A7 Midplane board assembly does provide these for all of the
different instrument power supplies as well as many of the power supply status
lines. A complete list of these can be found in Table 12-3 and the location of
each can be seen in Figure 12-2.
Additional Power Supply Regulation
There are two analog power supply regulators on the A7 Midplane board
assembly. They are the +3.3VA and -5.2VA supplies.
The +3.3VA supply is regulated down from the instrument +5.1VA supply while
the -5.2VA supply is regulated down from the -7VA instrument supply.
Both of these supply voltages have test points and LEDs on the A7 Midplane
board assembly as seen in Figure 12-2.
Instrument Secure Storage
This is Non-volatile storage of instrument model number, serial number, and
software license keys. While the license keys are also contained on the C: drive
of the instrument, the model and serial numbers are only saved in this secure
memory. There is no way for the user to access this memory in any way. This is
reserved for the factory and field software when needed for instrument
initialization, as well as the instrument software when installing an option
license key. If for some reason any of these cannot be remembered by the
instrument there could be a problem with this memory and the A7 Midplane
board assembly would need to be replaced.
Power Supply Dithering
A triangle wave of approximately 100 Hz is generated and goes directly to the
A6 Power Supply assembly. This is used to frequency modulate the power
supply switching frequency for the purpose of lowering any power supply
related interference.
If for some reason the level of the power supply related interference is higher
than normal this circuitry, or the A6 Power Supply assembly, could be suspect.
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