HP 1050 HPLC Autosampler: plunger home not found

[LadyMcGuyver]

Hello-

I tried searching the forum for the answer to this question and wasn't able to come up with anything. I'm getting a little desperate so any help you can provide would be appreciated. I'm going to be a bit verbose, in the hopes that more info can give more insight to my problem.

I have two HP 1050 HPLC systems; they are both very old, but sturdy machines that I believe still have some life in them with the proper care. So I'm fully prepared to take the blame if this is my fault.

We moved office locations recently, so my machine room had to be completely broken down, dried, moved, and reassembled ( ). Purging the lines took forever, and once that was all set up, one system works great. The second system does not. These are independent HPLC systems, each run off a separate computer.

For the injectors, I have a dental air compressor with a 2-way split valve to run both of the autosamplers for the two units (it is set to provide 5 bars of pressure). This set up worked fine at the old office.

Now, when the "not good" unit starts up, the normal exhaust sound that happens after the needle moves up and down is so WEAK. Instead of that strong PPPFFFT sound, I'm getting more of a gasp, 'eh,' and the error returned is E22: Plunger home not found. The needle seems to move okay, and I even dug out a spare autosampler and swapped the air valve solenoid from the spare unit - still having the same error. I don't see/hear any air leaks anywhere, I tried swapping the air lines from each machine and the "good" one runs the injector set up just fine with a great exhaust sound.

I'm attempting to go through the manual and run the service tests using the keypad on the unit, but that's not seeming to be too helpful. I'm more inclined to think that this is some sort of electrical/internal programming error, since it wasn't shaken up too much during the move, I doubt it's loose hardware. Just to be safe, I checked all the connections to the board just behind the needle motor and it all seems secure.

Any ideas on what I can do to diagnose the problem? I'm not ready to give up on my ol' buddy just yet!

[HPLC chemist]

I would almost think you have a 'kink' in the air line somewhere or something heavy is sitting on it.

[LadyMcGuyver]

you think a kink maybe in the unit lines inside? I've switched the external line between the two machines and the "good" machine gives great injections using either air line.

[uzman]

I faced the same problem in the past : if available , change the whole pneumonatic unit driving the 6 way valve.
Actually , the problem originates from the solenoid valves on the unit .

[Consumer Products Guy]

1050 autosamplers can be a little touchy. First of all, stainless steel plunger guide rails should be cleaned with methanol using swabs, no lube.

If mine, I would try a few psi higher air pressure, or lower air pressure on the balky unit; some can be touchy to slightly low or high air pressures. We had small inexpensive pressure regulators for each 1050 autosampler to reduce pressure to operating level, all fed by same air compressor that was set to slightly higher pressure. The compressed air must rotate the tray, as well as operate the needle assembly.

And since it's a 1050, I'd concentrate just on that module, using on/off button up front (and not software), until the issue is resolved.

[uzman]

According to my knowledge , air pressure only actuates the 6 way injection valve , neither the tray nor the needle assy, they are driven by step motors.

[mckrause]

I agree - the solenoid valves leak. The other problem we've had is a leak at the hose connection on the back of the instrument. H-P outdid themselves by going ultra cheap on that fitting (I mean, really, what could a good Swage fitting have cost? $5?). I've had cracks occur in that fitting and connection, and it is not a fun day trying to change that thing out! Worth it, but definitely not fun.

[LadyMcGuyver]

Hello all-

Thank you for all of the replies. I was lucky to have two autosampler units, and I only needed one to work. I did end up getting the unit to work, so I wanted to resolve that here as well in case anyone has a similar problem later down the line.

So here's a summary of all that I tried and what didn't work. The error was still E22: Plunger home not found.

I first swapped the solenoid units (with all the green air tubing connected to it in 5 places) - no change to the unit.

I then removed the analytical head and replaced the plunger seal. No change.

From my "not used" unit, I stole the optical sensor that attaches to the metering device and swapped that in on my 'good' unit - Depending on where I mounted the sensor (moves forward and back with loose screws), I could get either 1) the same error (E22) or 2) a horrible loud sound coming from the Metering device motor (round black piece to the left of the analytical head) that wouldn't stop until I turned the unit off. so I put it in position 1 and essentially - no change.

Finally, I was pretty convinced it was the metering device, so I removed the two screws (one into the back panel and one going down to connect to the 6-way valve), and unhooked the two plugs from the board (metering motor and metering sensor. Metering motor is labeled as such and metering sensor is labeled "met. pos. sensor"). The whole piece lifted out of the autosampler and I replaced it with the metering device from my "not used" unit. Powered it up and this solved the problem

Again, thank you for all the helpful suggestions!! I did a lot of "well just try it" work, and your suggestions were great. Hopefully this can help someone in the future!!