Chromatography Forum

Hello chromforum

I have been reading your forum for a while know to help me understand things better about the 5890 I work with. However I am at a loss right now.

I recently noticed that the TCD had stopped working properly. The TCD (detector slot A) is relatively new and the lab I work in rarely uses it (FID is used more in detector slot B)

It seems that someone had fiddled with the unit and the temperature probe broke off (it is a regular 100OHM PRT temperature probe) and I went to replace it. Upon replacing it, the unit gives me many errors (ADC offet, ATTN1, DETA TEMP RANGE, etc). I notice that NONE of the other temperature sensors work on the machine (I check the temperature of the oven, inject A, B, detector B and they show maximum values or really strange values).

I noticed that if I were to short the two temperature wires together, all the errors go away EXCEPT for the DETA TEMP RANGE (reads -180C). All the other probes will read properly at 30C.

I am at a loss for what is going on here. The probes are all testing 100% perfect. I used 3 different ones and the same results.

Just to be clear -- there is a bundle of wires coming out the front of the TCD that includes the heater wires and the RTD wires. The RTD wires attach to the mainboard (not the detector board). You used the manual or otherwise ensured that the wiring was correct when you put it all back.

I would focus on the wiring. You ruled out a faulty RTD. Based on your observations about shorting the wires, it sounds possible that you have the 3 wires mixed up. There is usually two red wires which are connected near the RTD element, used for sensing the resistance of the wire run to/from the RTD. Measuring red to white is the total resistance of the RTD plus wiring, so the resistance of red to red is subtracted from that to get the RTD value more accurately.

But maybe you knew all that...