Inlet problem on a 5890

[GregK]

Hello all. I'm rather new to GC, but the most experienced at my workplace (5 years using, only 2-3 troubleshooting). I'm not afraid to take things apart and put them back together in an attempt to make them work, so I've been given the "instrument troubleshooter" job. I also (usually) know how to find what I need somewhere on the internet, but the great interweb (a series of tubes, you know) has failed me this time. As I work second shift, people on first shift break things and leave them for me to fix; or worse, try to fix them first. Anyway...

Today I came in and they told me the 5890 isn't working. We have a 6890 as well, both controlled with ChemStation. The 5890 has two inlets: packed in front, split/splitless in back. The front inlet, apparently, stopped working today. They tell me it was ready something like 800°C when it was actually cool enough to touch. They "tried some things" and turned it off and back on. Now it tells me there is no inlet install on the front (both on the front display and in ChemStation).

This sounds to me like an electronics problem, something I have little to no experience in.

So, my question: How do I/can I reinstall the inlet to get the software to see it?

Thanks in advance for your help.
-Greg

[Ron]

It appears you have a bad temperature sensor in the front inlet, as indicated by the temperature reading of 800C. I don't know if this has anything to do with the inlet not being recognized, but it is a problem that has to be fixed.

[AICMM]

GregK,

No front inlet being recognized usually means someone disconnected the heater and RTD from the main board. You can get replacement heaters and RTDs for 5890s from Restek and they work quite well.

Best regards.

[GregK]

Thanks for the replies.

Well, I don't think anyone has disconnected anything... But one never knows. Anything more complicated than "turn off and turn on" usually waits for me. Any way this could happen spontaneously?

How can I check / where is the RTD board?

My assumption was that the temp sensor went bad and took other things with it when it went.

I guess we'll just use the back inlet until this gets fixed...

-Greg

[coffee bean]

Thanks for the replies.

Well, I don't think anyone has disconnected anything... But one never knows. Anything more complicated than "turn off and turn on" usually waits for me. Any way this could happen spontaneously?

Yes. Thermal stress can damage any cable in the long run.

How can I check / where is the RTD board?

Just follow the cables going to the inlet. They are the heater/sensor cables. My suggestion is to replace the heater/sensor assembly instead of only replacing the sensor.

[Peter Apps]

Before you replace anything use a multimeter to check for continuity of the heater element and temperature sensor. Unplug the board end of the cable and test at the contacts.

Peter

[GregK]

Sorry for the delayed response. I also do analytical work and everyone thinks that a broken instrument is less important that making production happy. Anyway, I got a chance to test the continuity. Unless I did it wrong, we do have continuity. (Unplugged plug from board, tested between the two sides of plug at the "INJ A" part.)

I guess this means I need a new sensor/heater. The only one I can find in the Restek catalog says it is for the split/splitless injection port. We have a packed column on that injector, is there any real difference in the heaters/sensors?

One last thing to anyone with experience ordering from Restek: Why do they list the heater and sensor separate at $105 and $119 and a heater/sensor kit for $282? Doesn't that make it cheaper to order them separately? (Catalog # 22069, 23035, & 22068.)

Thanks again,
Greg

[Peter Apps]

Hi Greg

If you have continuity through the sensor and heater they cannot be broken (well they can but it would need something obscure like a short to the heater capsule). Looking back at my post maybe it was not clear - you test at the contacts on the end of the cable after you have unplugged it, not at the contacts on the board. While you are doing it you can check for a short to the heater body.

For equivalence of parts you need to check Agilent/HP parts numbers, or ask Restek.

I have only ever had good service from Restek, my guess on the prices is that they reflect fluctuations in stock turnover and what price they paid for them. The real advantage of ordering separately is that you do not need to replace the sensor when it is only the cartridge that is bust, and vice versa. Check though that the cable terminations are the same - the individual bits might have bare cable ends which can be a PITA to fit to the plug.

Peter

[AICMM]

GregK,

The difference in price also reflects the fact that the combined sensor/heater comes in a fiberglass sheath as per the factory original whereas the sensor or the heater by itself does not. That costs them a bit in materials and time which they have to recoup.

It is not quite good enough to just have continuity through the sensor, you should have around 100 ohms on the sensor since it is an RTD. Also, make sure the cables to the sensor are in good shape as any fraying o the leads can easily lead to shorts which make the system unhappy. If you tested the RTD in place, you could have continuity because both leads are shorting to the block so measure resistance instead.

Finally, I am pretty sure the packed port heater and the splitless/split heater are the same but Peter is right, just ask Restek. It is much more common for the sensor to die than the heater though.

Best regards.

[aldehyde]

Yeah at 0 C the resistance on the sensor should be 100 ohms, and it increases slightly as temperature increases (at 20 C it should be like 107 ohms).

If you're getting 0 or infinity the sensor is broken, and the instrument reporting either -273 C or +800 C would correspond to these.

[GregK]

Okay, so we ordered the part from Restek. It came in today and I started taking the 5890 apart to work on it. I got directions from ...somewhere online (can't remember)... in pdf form that look like scans of an HP service manual. They tell me I need "an AMP pin extraction tool (8710-0614)" to remove the pins from the J9 connector, and "an AMP pin extraction/lance rest tool (8710-1542)" to remove the pins from the P7 connector. Where can I get these tools?!? Doing a google search for the part numbers gives me nothing; same result searching Agilent's site. Using google, I can find a place (crawfordtool.com) that sells the first tool, but I can't find mention of the second.
Please help, I got the part delivered overnight so I could get the system up and running this week. Now I have to wait for tools?
Lesson learned: Check install directions before ordering part.
Thanks again.
-Greg

[Peter Apps]

Hi Greg

If you have RS components in your part of the world try them - you can order online and delivery in fast even in southern Africa.

Peter

[Consumer Products Guy]

You might be able to use a small paper clip or similar. I have swapped the leads on these connectors before, I'll look up where I got the tool when I'm at work.

[GregK]

Okay, now I'm starting to get frustrated...

I can get the wires out without the special tool, I think (thanks Consumer Products Guy). If not, I can get them overnighted. Since I can't work on that end, I started work on the other (inlet) end. I can not get the heater or sensor out of the block. The lines that run into the inlet are in the way, kind of wrapped around the block. The service manual says "carefully slide hear and sensor cartridges out of the heated block portion of the inlet". There are lines that are in the way, and a brass (?) plate in the way as well. I don't want to pry on the 10+ year old stainless steal lines and break one, but I don't really see any way to get the thing apart. Sorry for the vagueness, but I can't think of how to describe it better.

I'm trying to get pictures uploaded, but web-blocker at work won't let me onto any image hosting sites. I'll bring in my camera and take some pics and upload later.

Thanks, yet again, for help.

[GregK]

Well, that last post can be ignored, mostly. The sensor looks like it should slide out the top of the block, so I gave it a tug (gently, of course). The wire leads came off and the sensor is still in the block.

Now I need to get it out.

Oh and the heater itself doesn't match, so that isn't getting replaced. The one from Restek is ~9.5mm in diameter, the one in the block is ~6.6mm.

Nothing is going right for me... I can't wait for Christmas break.

-Greg