Changing a detector temperature sensor (ECD)

[chemwipe]

So I started getting an error on my HP5890

FAULT: DETA TEMP RDG

and the temperature reading for the detector was changing rapidly from 25-400 and all over the place.

I restarted the instrument, same thing happened.

EDIT: Tried to dry some glassware in the same GC just now, and the oven temperature won't even change.

Sounds like I'll have to replace the sensors for not only the detectors but the oven as well...?

Any tips, tricks, hints? I haven't done this before.

Thanks,
John

[Consumer Products Guy]

The little sensors just pull out, attach to circuit boards. You'll need to remove some covers. Figure to take 1.5 hours.

[Peter Apps]

Hi John

I think that the 5890 (and nearly all others) use 100 ohm platinum resistors as temperature sensors. These are pretty rugged, and under GC conditions with nobody fiddling with hardware I would expect them to last forever. Sadly I think that it is more likely that you have an electronics problem, the best that you can hope for is a board that is not seated properly, or some loose connections.

Peter

[AICMM]

chemwipe,

Sounds like the RTD went bad. Don't worry about the oven or electronics until after you have replaced the ECD RTD since the oven RTD is probably fine. One of the things about the HP RTD's is that they get chafed at the detector which can eventually lead to an exposed lead and a short which causes the fluctuations you see in the temperature. CPG is right, about 1.5 hours, with covers removed, make sure you unplug the GC and let everything cool before diving in.

Best regards.

[chemwipe]

CPG:

The little sensors just pull out, attach to circuit boards. You'll need to remove some covers. Figure to take 1.5 hours.

Is it really that easy? It was a pain getting the sensor out which was attached to the oven shroud.

Peter:

Sadly I think that it is more likely that you have an electronics problem, the best that you can hope for is a board that is not seated properly, or some loose connections.

NONE of the temperature sensors seemed to be working (oven, detector, injector) before I took the GC apart- replace each sensor or electronic issue? How/what can I check?

AICMM:

Sounds like the RTD went bad. Don't worry about the oven or electronics until after you have replaced the ECD RTD since the oven RTD is probably fine. One of the things about the HP RTD's is that they get chafed at the detector which can eventually lead to an exposed lead and a short which causes the fluctuations you see in the temperature. CPG is right, about 1.5 hours, with covers removed, make sure you unplug the GC and let everything cool before diving in.

RTD = R____ Temperature Detector?
I've already removed the oven sensor...maybe I shouldn't have. It seemed easier to start there than the detector sensor...

Kind of frustrated with this whole situation, as I'm the only one who works with the GCs. So imagine trying to take one apart and troubleshooting while trying to keep up with extracting samples and running them.

Again, I've never done this before, so I'm guessing the 1.5 hour estimate might be a little off, haha.

I appreciate you all taking the time to answer.
Anyone else have any tips or hints?

Thanks,
John

[Peter Apps]

This is certainly an electronics problem. How good are you are fixing stuff ? Your best hope is a loose connection, if there is a blown board component your chances of getting a replacement are slim because Agilent do not support 5890s. Turn off the instrument at the mains, remove the side covers, unplug and replug every lead that you can see, and every board that plugs into another one. Examine contacts for signs of dirt or corrosion and clean them if neccesary. Examine the boards in detail for heat damge or damaged components. If you find a hot spot or a damaged component you might be able to identify it and replace it.

Alternatively look around for an independent lab support company that operates in your area and ask them to have a look at it.

Good luck.

Peter

[chemwipe]

This is certainly an electronics problem.


How good are you are fixing stuff ? Your best hope is a loose connection, if there is a blown board component your chances of getting a replacement are slim because Agilent do not support 5890s. Turn off the instrument at the mains, remove the side covers, unplug and replug every lead that you can see, and every board that plugs into another one. Examine contacts for signs of dirt or corrosion and clean them if neccesary. Examine the boards in detail for heat damge or damaged components. If you find a hot spot or a damaged component you might be able to identify it and replace it.

Ok, here we go... (this did take more than 1.5 hours, haha)







I'm not too good at electrical stuff - not sure what I'm looking for here, I was about to totally take out the oven temp sensor when I read the post saying that this was an electrical problem:



I found where the oven sensor wires go and reseated it, thinking that would work:



But it didn't. I got these errors after hooking everything up. I reseated all the wires, blew compressed air through all the boards and inspected them for any obvious problems and got this:








Any suggestions? I hope the pics help.

Thanks in advance!

John

[GasMan]

Looking at your pictures, I assume that you also have an inlet and a detector in the front position. Do you get the same sort of error if you look at these temperatures. If yes, I would gues that you have a main board problem, as it unheard of all heated sensors going defective at the same time.

Gasman

[Ron]

Looking at the pictures I would estimate a minulmum age for the instrument of 20 years old. THis is probably a main board problem, and you may be able to find a used main board, but the chance of finding a new board is essentially zero. Any time you get used parts there is a risk of parts not working, or failing soon. You can probably get the instrumnet running agian, but unless your time is free you may end up spending as much getting this going as it would cost to replace this instrument.

[chemwipe]

Looking at the pictures I would estimate a minulmum age for the instrument of 20 years old.

Date on the inside reads 10/15/86!

THis is probably a main board problem, and you may be able to find a used main board, but the chance of finding a new board is essentially zero. Any time you get used parts there is a risk of parts not working, or failing soon. You can probably get the instrumnet running agian, but unless your time is free you may end up spending as much getting this going as it would cost to replace this instrument.

Where would you suggest I get a new main board? I have a HP5890 Series II in my GC graveyard that I can probably get parts from, although I don't even know what it was used for: both detectors have been removed.

Thanks,
John

[Ron]

The Series II had a different main board that the 5890A, I don't think they are interchangeable. THere used to be a kit to upgrade a 5890A to a 5890 Series II, and it had a lot of things to change out for the upgrade.

Try searching for 5890 service using Google or your favorite search engine. There will be a lot of third party service providers, and one of them may be able to supply a main board.

[chemwipe]

unless your time is free you may end up spending as much getting this going as it would cost to replace this instrument.

Just got a quote:

$1637 for the board
$181 for extension cables
$133 for a new eprom

Even if I did this myself, I'm sure this would be cheaper than replacing the instrument.

Anyone in here replace a main board here before?

John

[AICMM]

Chemwipe,

I have replaced main boards a couple of times. Considering how far you have gotten with the removal of other parts, it should not be that hard for you to complete. I would also say it is also pretty intuitive.

Best regards.

[chemwipe]

I have replaced main boards a couple of times.

This will be the first time the main board has been replaced. Today is that GC's 23rd birthday, haha!

Considering how far you have gotten with the removal of other parts, it should not be that hard for you to complete. I would also say it is also pretty intuitive.

The hardest part might be getting the $1000+ order approved!

Thanks to everyone who replied!
John

[chemwipe]

Chemwipe,

I have replaced main boards a couple of times.

AICMM-

I forgot to mention this: when I got the quote for the main board, I was told that the board I would purchase would not be the same as the board that is currently in the GC (see the pics in the original post). The sales rep said that it's a smaller board, hence the need for the extension cables (as well as a *recommended* on-site service call). Is that what you've replaced?

John