Hi, I have a PXI-1042Q chassis (that used to work without problems) that after turning on the power, the green power LED turns on and off with an inconsistent pattern. I have seen the pattern when the air intake temperature is high (off then blinks twice and then off again) but this one is different. It just randomly shuts off after a few seconds, stays off for a few more seconds, then turns back on for a few more seconds etc. The on and off periods are somewhat random, but always last anywhere from a few seconds (2 or 3) to several seconds (sometimes over 10 seconds but never over a minute). Power from the supply seems ok. All power rails are within spec: +5V, +3.3V and +/-12V. This is both on the backplane and the rear monitor. I disconnected the NTC thermistor for the air intake temperature and seems to read about 5.8kOhm. If I power the chassis without the thermistor, I observe the same behavior with the power LED. Fan speed is low (when the switch is set to Auto) If I short out the thermistor terminals on the fan control board, the expected over temp blinking pattern is observed (off, blink three times and then off again). Also, the fans run at max speed when the fan switch is set to auto. The above leads me to believe that the power supply and the fan control board are ok. Are there any ideas that could point me in the right direction? Could this be a problem with the backplane board? The original symptom was that the Windows 10 host stopped recognizing the chassis and the instruments via MXI-4. Any help will be greatly appreciated. Thanks!

PXI

PXI-1042Q green LED turns on and off with inconsistent pattern

Hi,

I have a PXI-1042Q chassis (that used to work without problems) that after turning on the power, the green power LED turns on and off with an inconsistent pattern. I have seen the pattern when the air intake temperature is high (off then blinks twice and then off again) but this one is different. It just randomly shuts off after a few seconds, stays off for a few more seconds, then turns back on for a few more seconds etc. The on and off periods are somewhat random, but always last anywhere from a few seconds (2 or 3) to several seconds (sometimes over 10 seconds but never over a minute).

Power from the supply seems ok. All power rails are within spec: +5V, +3.3V and +/-12V. This is both on the backplane and the rear monitor.
I disconnected the NTC thermistor for the air intake temperature and seems to read about 5.8kOhm. If I power the chassis without the thermistor, I observe the same behavior with the power LED. Fan speed is low (when the switch is set to Auto)
If I short out the thermistor terminals on the fan control board, the expected over temp blinking pattern is observed (off, blink three times and then off again). Also, the fans run at max speed when the fan switch is set to auto.

The above leads me to believe that the power supply and the fan control board are ok. Are there any ideas that could point me in the right direction? Could this be a problem with the backplane board?

The original symptom was that the Windows 10 host stopped recognizing the chassis and the instruments via MXI-4.

Any help will be greatly appreciated. Thanks!