Hello.
I have an issue with a piece of equipment I was asked to troubleshoot today at work. I was preoccupied with another issue I was working on but that is another story (which I might discuss too haha). Long story short, I gave it a quick look over and noted the fault symptoms.
Anyhow, the equipment is an Agilent Technologies Micro GC (gas chromatograph)
https://www.electro-tech-online.com/custompdfs/2009/11/3000microGC_especi.pdf
GCs are electromechanical, temperature controlled lab equipment with analog sensors amplified and converted to digital with signal voltage integrated vs. time axis. Acquisition software on a computer retrieves the real-time data and creates files.
It is a portable apparatus, so for flexibility the power supply is external giving the option of battery power in certain applications. My facility has only ever used the power supply, no batteries available.
The supply is a switcher of good quality, black box type with AC cable and a 4 pin DC cable with a keyed connector. 15 VDC, 6.6 amps. Small cooling fan built in with vents.
The fault condition was no communication with peripheral PC. A secondary symptom was the power LED on the main switch, the operator mentioned that it seemed dimmer than usual.
I removed the cover and found both motherboards (identical boards for two-in-one testing) were powered up, board mounted LEDs indicating operation.
I depowered the instrument to visually inspect it, and unplugged the power supply. I found evidence of excessive heat, the external label was discolored, brown and gray like it had been cooked. I reconnected it and applied power, and felt vibration. Inspection confirmed the cooling fan was binding, turning slowly, stalled.
I checked voltages with my multimeter:
Found 15 volts as expected. Checked ripple...intermittent evidence of .5 volts of AC. Checked frequency, 24 Hz???? Huh?
I know switchers use high frequency to reduce transformer size. I wouldn't necessarily expect 60 Hz. Wasn't sure why 24 Hz would show up.
I ordered a new supply from Newark, but this kind of puzzled me.
I might expect ripple to cause noise in the communication to the PC, so I fel I might have found the issue, but I was hoping someone with more knowledge could confirm that 500 mV of ripple would be out of the ordinary for a SMPSU, and explain why 24 Hz might show up and that this would be disruptive on a serial port cable.
Thanks in advance.
I have an issue with a piece of equipment I was asked to troubleshoot today at work. I was preoccupied with another issue I was working on but that is another story (which I might discuss too haha). Long story short, I gave it a quick look over and noted the fault symptoms.
Anyhow, the equipment is an Agilent Technologies Micro GC (gas chromatograph)
https://www.electro-tech-online.com/custompdfs/2009/11/3000microGC_especi.pdf
GCs are electromechanical, temperature controlled lab equipment with analog sensors amplified and converted to digital with signal voltage integrated vs. time axis. Acquisition software on a computer retrieves the real-time data and creates files.
It is a portable apparatus, so for flexibility the power supply is external giving the option of battery power in certain applications. My facility has only ever used the power supply, no batteries available.
The supply is a switcher of good quality, black box type with AC cable and a 4 pin DC cable with a keyed connector. 15 VDC, 6.6 amps. Small cooling fan built in with vents.
The fault condition was no communication with peripheral PC. A secondary symptom was the power LED on the main switch, the operator mentioned that it seemed dimmer than usual.
I removed the cover and found both motherboards (identical boards for two-in-one testing) were powered up, board mounted LEDs indicating operation.
I depowered the instrument to visually inspect it, and unplugged the power supply. I found evidence of excessive heat, the external label was discolored, brown and gray like it had been cooked. I reconnected it and applied power, and felt vibration. Inspection confirmed the cooling fan was binding, turning slowly, stalled.
I checked voltages with my multimeter:
Found 15 volts as expected. Checked ripple...intermittent evidence of .5 volts of AC. Checked frequency, 24 Hz???? Huh?
I know switchers use high frequency to reduce transformer size. I wouldn't necessarily expect 60 Hz. Wasn't sure why 24 Hz would show up.
I ordered a new supply from Newark, but this kind of puzzled me.
I might expect ripple to cause noise in the communication to the PC, so I fel I might have found the issue, but I was hoping someone with more knowledge could confirm that 500 mV of ripple would be out of the ordinary for a SMPSU, and explain why 24 Hz might show up and that this would be disruptive on a serial port cable.
Thanks in advance.