HP 5972 MSD - Fault 512 - Detector HV Supply

[AThompson]

I am experiencing a fault 512 with my HP 5972 MSD. The fault results in the message “Difficulty in the Detector HV Supply”. I am wanting to confirm what replacement part I should consider first? The DC power supply, the power distribution board, or something else? If anyone has any thoughts, please let me know. I have checked all the connections leading to the electron multiplier and everything seems fine. All connections are also secure to the analyzer and the vacuum level is below 100 mTorr.

I’ve attempted to do the air/water check several times now in the diagnostics/vacuum section of ChemStation. Every time, I have been unable to turn on the detector due to the HV supply error, except for one time that resulted in the error “Difficulty in the mass filter electronics”. I’d like to start troubleshooting first with the detector HV supply error and move forward from there.

Thanks for any suggestions, I appreciate it!

[James_Ball]

I am experiencing a fault 512 with my HP 5972 MSD. The fault results in the message “Difficulty in the Detector HV Supply”. I am wanting to confirm what replacement part I should consider first? The DC power supply, the power distribution board, or something else? If anyone has any thoughts, please let me know. I have checked all the connections leading to the electron multiplier and everything seems fine. All connections are also secure to the analyzer and the vacuum level is below 100 mTorr.

I’ve attempted to do the air/water check several times now in the diagnostics/vacuum section of ChemStation. Every time, I have been unable to turn on the detector due to the HV supply error, except for one time that resulted in the error “Difficulty in the mass filter electronics”. I’d like to start troubleshooting first with the detector HV supply error and move forward from there.

Thanks for any suggestions, I appreciate it!

100mTorr would be the vacuum between the diffusion pump and the rough pump, which should drop to around 30mTorr once everything is running well, definitely below 70mTorr.

Do you have an ion gauge for measuring the actual analyzer pressure? If that is too high it can give the same HV error, it should be in the 5*10^-5 Torr range or lower for best results.

I can't remember if there is a physical switch on the front inside the covers for a 5972 for EI/CI operation or not, I know they were present on the 5971. If the switch is there move it to CI, this will disable the pressure check which it does using the filaments and will allow you to scan even if the analyzer pressure is high.

If it is not a pressure problem, since you have errors for both HV and Mass Filter it could be a Top Board problem as both of those are controlled there. Look to the rear of the board, starting just behind where the RF Coils are housed and see if any of the resistors are swollen or cracked or if any of the capacitors have burst. Power surges can cause these to go bad and it will give you many problems.

Top board and Main Board both have several voltage test points labeled with +5v or -5v and other voltages which you can use to test if you are getting the proper voltages to the boards, if low it could mean the power supply is bad.

[AThompson]

Thank you for the response!

I checked the test voltages on the main board and here are the results:

-15V --> -15.1V
+15V --> +14.9V
+5V --> +5.0V
+24V --> +27.1V

I don't know what to make of the +24V test point result. I measured it twice. It seems that 27.1V is too high? Is there a good way to know whether the problem lies on the main board itself or from the power supply or power distribution board? I tested the fuses in the power distribution board, and both are good. The diffusion pump is working and the fan is blowing (which is a good sign for the power distribution board). I'm suspecting either the main board or power supply.

Incidentally, I notice that even though the transfer line is set to 300C from the 5890 GC, the source temperature only read around 110C after remaining there all weekend. And the system vacuum varies somewhat as I watched it this morning. Every few seconds when it updates, it would vary between 70 - 120 mTorr range.

Any additional thoughts would be greatly appreciated - thank you!

[James_Ball]

Thank you for the response!

I checked the test voltages on the main board and here are the results:

-15V --> -15.1V
+15V --> +14.9V
+5V --> +5.0V
+24V --> +27.1V

I don't know what to make of the +24V test point result. I measured it twice. It seems that 27.1V is too high? Is there a good way to know whether the problem lies on the main board itself or from the power supply or power distribution board? I tested the fuses in the power distribution board, and both are good. The diffusion pump is working and the fan is blowing (which is a good sign for the power distribution board). I'm suspecting either the main board or power supply.

Incidentally, I notice that even though the transfer line is set to 300C from the 5890 GC, the source temperature only read around 110C after remaining there all weekend. And the system vacuum varies somewhat as I watched it this morning. Every few seconds when it updates, it would vary between 70 - 120 mTorr range.

Any additional thoughts would be greatly appreciated - thank you!

Normally the source temperature would be around 170c with the interface set near 300c, it is possible that the end of the interface is not touching the gold adapter that screws into the side of the source. That is where the heat transfer takes place from the transfer line to the source. The vacuum reading should also be more stable so maybe there is a leak where the interface attaches to the side of the analyzer. If the sealing ring there is not perfectly seated it may be causing both problems. Also make sure you didn't do what I did once and forget to put the gold adapter back into the side of the source

On the top board there is a square box at the back of the board where the signal cable connects that steps up the voltage for the EM. I believe that one is fed from the +24v, I will have to see if I still have my schematics around somewhere. You have plenty of voltage it seems so that could be going bad, but the fact that it did scan but give the Mass Filter error still make me think it is related to either pressure or top board.

Was it running stable then gave the problem after venting and pump down, or did it just all of a sudden stop working and give the errors without it having been vented?