Varian 3600 GC

[mayuri]

Hi .. i have a very peculiar problem and my work seems to have been stopped due to this.
I use a Varian 3600 GC, my project is mainly for testing hydrogen produced from partial oxidation of propane. But i am a new student and i am just trying to run some basic samples like air to observe the plot.
We have observed that the TCD was faulty and got a new one. But varian doesnt manufacture any more TCD detectors for 3600 and so we bought a valco instruments micro volume TCD.
Now the old detector had a connection to TCD board (there are many other boards too eg. one for FID, one for temperature control etc) and all boards are connected to a motherboard.
This new detector has an externally controlled controller and has no connections with the TCD board now.
We had all the connections but it is showing lot faults mainly that it is assuming it to be an open circuit and assuming an infinite temperature and hence has turned the switch off on temperature board. So even though my TCD doesnt interact with the GC for oven and detector temp controls , it is assuming it to be an open loop and so i am not able to raise the temperature of any of the unit.

I tried removing the TCD board too but it still shows an error that "main power connector" is open .
I will be really glad if somebody helps me out

Thank you
Mayuri

[AICMM]

Mayuri,

1) There are a number of people who could rebuild your 3600 detector.
2) with the power off, try opening and re-closing all of the board latches to see if the will re-seat.
3) You should be able to turn off the TCD in the inst. config so that it does not care about the current TCD stataus. If you take this route, you should have the TCD board fully installed and connected but it should power up with the TCD turned off.
4) Your final option is to remove the TCD board and remove the heater controls for the TCD from the heater controller board (main board?) and replace any of the thermocouple leads with a small resistor but I cannot remember what size resistor.

Best regards.

[mayuri]

Hey thanks a lot for the reply.
firstly, my advisor has ordered a new TCD and so the first option is ruled out. second, we have tried opening and reclosing all the latches.
Third, we have made sure that TCD is turned off in the GC control as i said that the new TCD detector and oven is not controlled by the GC anymore.
But it shows the fault as soon as i start the GC, i mean i dont have to wait till i set the conditions.. even though, i have tried to turn TCD off thru GC, but it still shows the faults. It shows fault 207 and fault 19, both of which indicate that some of the units have reached a temp above 450 C which is not true and dats why it is turning off the main switch on the temp board off.

Now as per your suggestion, i have removed the TCD board and the heater connection on the temperature controller board too. But i dont know ... it still shows error, though this time its different kinda error which says "main power connector could be open"

I have tried asking many people from various depts in my school too but no body seems to know . My last option would be calling Varian..

But i had a doubt that would removing TCD board just enough ?? wat was it about replacing TC leads with resistors ??? could u elaborate ?

I would really appreciate any kind of suggestion............

[mayuri]

did u mean like if i take out the pin for TCD oven control should i be replacing it with a pin with a resistor so that it reads it as null ?? or a no circuit ???? If thats the case, is it the only change apart from removing the entire TCD board or should i be changing something on the motherboard too like a power pin or something ???????

[AICMM]

Mayuri,

For a 3400:

Fault 207: "specific zone is overheated"... "Remove high voltage cover. Unplug the heater and probe connector corresponding to the the overheated zone... and replace it with the probe simulator plug. "

Fault 19: "Fuse F2 on the Mother board is blown."

I am confident the same will apply for the 3600.

I would contact Varian and see if they still offer a probe simulator plug and if not see if they can tell you how to build one. In the past I have found their tech support to be very helpful.

Best regards.

[mayuri]

Hey AICMM
Thanks a lot once again. Yes for 3600 , the errors mean the same.
We have checked all the fuses, and all of them are good.
And it shows fault 207 because as i said, it thinks it to be an OPEN CIRCUIT.. which means it assumes an infinite temperature.
I have removed a pin from the temmp controller board for the TCD but i think as u said, i should put up a null resistor or something like it so that it acts like a jumper and tricks the GC ..

I dont think even replacing probe simulator would be good because it would still detect an open circuit and assume an infinite temp.. wat do u say??

[mayuri]

Because apart from fault 207, it also showed fault 19,20,22 and 36 !!!!

[mayuri]

Hey n one more thing ....... ive just spoken to Varian technical support, but they right away said that they dont know the solution , infact they dint even know dat valco has started manufacturing TCD.

I ll be glad if you suggest something or other.
The only option which i seem to have is not to leave the pin open in the temperature board and replace it with a clip having a resistor.
But i dont know what resistor should be used.
We have a pin for auxilary oven too on the same temperature board , but we dont use that oven so that pin has a clip on it with a resistor which has a very low value .. about 0.09 or 0.9 mV ..

Please help me out .

[chromatographer1]

It used to be, I don't know if it pertains to this situation, but I thought at one time that Varian used GOWMAC's TCD in their gas chromatographs.

Perhaps a call to GOWMAC will be helpful? Just a suggestion.

best wishes,

Rod

[mayuri]

Thank you .
I have contacted GOWMAC.. but they said its essentially 3800 but they do provide detectors for 3600 varian too .
I just got a call back from Varian suggesting me to use a resistor of 100 Ohms as a jumper and see if it works , but they said they arent sure if this route would lead to a solution to all the faults or not .

[AICMM]

Mayuri,

If your temperature sensor is an
RTD, and it probably is, then most RTD's work around 100 ohms at room temperature more or less. So, replacing the blank space for the current temp sensor with 100 ohm RTD should be a good start. You should be able to measure the resistance of a different RTD (with GC off, perhaps the injector or another detector) and get a basic resistance starting point.

Valco has been making a TCD for years so your response from Varian is intriguing.

Best regards.

[chromatographer1]

Mike,

People in technical service sometimes have not been there for years and may not know about OTHER companies' equipment even if they have.

Now someone in sales who investigates the market may very well know that Valco has made TCDs for a long time, but technical service? I see no reason to assume that.

Only if they have seen issues of someone having a problem using a Valco TCD with a Varian GC would they learn that, and I doubt there are many Varian GCs with a Valco TCD.

It all seems reasonable to me in any case.

Hope things are going well for you at AIC, Mike.

Rod

[mayuri]

Hey guys ..
THANKS A TON !!!!!
I have replaced the plug with a 100 ohms resistance , dats called a "probe simulator" and its not showing any fault !! thank you so much, splly aicmm....
Ill do ask you for help if i need a suggestion with plots or anything .

Thank you once again ... !!!!

Regards
Mayuri