Chromatography Forum

Hi there.

I got here a Varian saturn 2000 GC-MS with some history, where on the MS part the diffusion pump control does seem to have some issues and I'm late to the party..

The fault message (I don't have it word for word unfortunately) runs along the lines of "the diffusion pump heater current being wrong".

The diffusion pump has the following type label: The unit is being run in Australia, so we got 230Vac/50Hz.

The history of the unit is the following afaik:

• the MS seems to have burnt the original diff pump heating element, which I assume has been 165V/250W (which has been thrown away by the guy who did the replacement with the next spare, so can't say how it looked like)
• the replacement then being put in is still here and it reads:

  Code: Select all

  WATLOW ST.LOUIS
  220V~ 250W
  TYPE CR 1328 09
  L2A-853

  the diff pump didn't work with this one and it was found out that it was 220Vac rather than 165Vac, so a new one was ordered
• now there is this one attached to the diff pump now (after it had been found the 220Vac is not correct), but the error is still the same

  Code: Select all

  WATLOW ST.LOUIS
  L2A-106 REV D
  165V~ 250W
  TYPE CR 1322 13

Currently the MS diff pump is disassembled and I pulled the power/control board out to check what's going on there.

Please check the following pictures for details (you can click on them to see a bigger version):


Now onto the questions I've got (thanks for reading so far):

• anyone got any advise what I should be looking for?
• Is it normal to have a 165Vac heater run in a 230Vac country?
• The 6-pole connector marked in the pics has got a free terminal, that on the board runs directly to the controller for (I suppose) some sort of sensing element that goes out to the diff pump, but it's not populated here. Is that normal or does the MCU on that board miss some sensor info?
• The 2 blue marked adjustable resistors on the controller board seem to be for Current/Voltage sensing of the power that is running through the heater.. any info on what to adjust these two resistors to?
• If the hardware is fine, what about the controller on the board and it's software.. can it be replaced/sourced from somewhere?
• Does anyone have a schematic of that board or would know where to get it from?

Thanks for your help, much appreciated.
Joan

No one got any idea?

Anyhow, I reverse engineered the diffusion pump power board as good as I could and found no faults. It seems to be working within spec - can't be sure on the MCU part though as I don't know it's program or what it expects on it's pins.

So I reassembled everything and started the MS up (no foreline pump) and got the following diagnostic message:

If one clicks on 'Reset' the MS starts up the system (again) and checks the diffusion pump heater current.
"THE DIFFUSION PUMP IS REPORTING A FAULT: THE DIFFUSION PUMP HEATER IS NOT DRAWING THE CORRECT AMOUNT OF POWER. IT MAY BE UNPLUGGED OR OPEN"



In the sequence of the screenshot above I tried:

1. startup
2. unplugged 6 pole connector
3. bridged the temperature cut off sensor (closed = no overtemp)
4. plugged 6 pole connector back in and turned current resistor 1/4th to the right
5. turned current resistor 1/4th more to the right
6. turned current resistor 3/4th to the left
7. turned current resistor 1/4th more to the left
8. turned current resistor back where it was

nothing helped so far.

Some when next week (if there is no reply here) I'll try the full adjustable spectrum for the current resistor and if that doesn't bear any fruit the MS is very very close to being thrown away.

• Does anyone know how to adjust the heater current sensor?
• Does anyone know what the 4 LEDs on the diff pump power board are for? What do they signal?
• Does anyone have a program or an idea where I could access the heater current sensor value?
• Has ever anybody replaced their diff pump heating element successfully?

Cheers,
Joan