Chromatography Forum

Hello all-

The pressure on my 5890 Series II is stagnant at a reading of 2.6. It's not changing at all - not during maintenance, not while changing the setpoint or while running the program.

Does this sound like there's something wrong the the EPC? I'm not getting any kind of error meesage on the display.

Wondering if there's something I may have overlooked. I recently changed the main board due an "EPP A NOT INSTALLED" error.

Thanks in advance for any suggestions!

John

Have you tried restarting the instrument? Turning off the gas supply entirely? What happens, and are there any errors on boot?

Assuming this is inlet pressure you have a column installed or a blank column nut attached right?

When you replaced the mainboard has it worked since and how long ago was the mainboard change? It could be a loose cable that has now worked its way out.

Have you tried restarting the instrument? Turning off the gas supply entirely? What happens, and are there any errors on boot?

Restarting the instrument gave the same result...haven't turned off the gas supply, will try that. And no, no errors on boot.

Assuming this is inlet pressure you have a column installed or a blank column nut attached right?

Haha, yes, there's a column installed.

When you replaced the mainboard has it worked since and how long ago was the mainboard change? It could be a loose cable that has now worked its way out.

I actually replaced the board on 11/14, a couple days later, I had the following errors on the 5890 display in the middle of a run:

FAULT: ADC OFFSET
FAULT: LINE SENSE
OVEN NOT READY
INJ A NOT READY
DET B NOT READY

A dialog box came up on the computer screen, and I clicked "Start Run." The sequence finished, and everything seemed normal.

About to check the wiring to make sure nothing's loose.

Thanks!

John

Ok-

Turned off the gas supply, no change in the pressure reading...wasn't sure if it was an electronic issue, so I changed the main board - same thing is going on, though.

Any suggestions I can try from here?

Thanks,
John

It's possible that the pressure control valve itself or the small board connected to the valve is not operational.

I ran into a problem once a few years ago with EPC on a 5890 in which the pressure setting would not change the actual flow. I fixed it by replacing the flow control valve. I have heard that the symptoms will be the same if the small board the valve connects to goes out. Also, when this happened to me there was no error on the GC, just total lack of pressure control. I may suspect the small board connecting to the valve because whatever damaged the main board may have damaged the valve controller board located in the EPC unit.

It's possible that the pressure control valve itself or the small board connected to the valve is not operational.

I ran into a problem once a few years ago with EPC on a 5890 in which the pressure setting would not change the actual flow. I fixed it by replacing the flow control valve. I have heard that the symptoms will be the same if the small board the valve connects to goes out. Also, when this happened to me there was no error on the GC, just total lack of pressure control. I may suspect the small board connecting to the valve because whatever damaged the main board may have damaged the valve controller board located in the EPC unit.

I was told that it was the EPC sensor:




so I replaced it - no change in pressure.

You mentioned the valve controller board, are you talking about one of these?


These are the ones that are in the middle of the main board:


Not sure what else I can check from here.

Thanks for the reply, Earl!

John

I was refering to the EPC sensor when I said small EPC board. Looks like that was not it. I thought you had replaced the main EPC board (the center board in your pic showing three boards). It could very weill be the flow controller valve itself went out which was what happened to me. One possibility to check is to try switching the EPC cord from one port to another and see if it is related to the main EPC board. Your pic with the "ones in the middle of the main board" shows the main EPC board. you have 6 cords coming out of this and you really need 2 at max if you have EPC on the front and back injectors (unless you have aux EPC). Try isolating the cord that actually is going to the EPC sensor and try using a different spot on the board (you'll have to change this on the GC key pad as well). Could be a bad spot on the board or cord, luckily you have spares to try. I would still get the part number for the flow controller cause that could be it.

Your pic with the "ones in the middle of the main board" shows the main EPC board. you have 6 cords coming out of this and you really need 2 at max if you have EPC on the front and back injectors (unless you have aux EPC). Try isolating the cord that actually is going to the EPC sensor and try using a different spot on the board (you'll have to change this on the GC key pad as well). Could be a bad spot on the board or cord, luckily you have spares to try. I would still get the part number for the flow controller cause that could be it.

Okay, I switched the cords around...when I removed the second cord (from the top) the pressure went to zero...

What settings do I have to change on the keypad?


John

Sounds like the second cord from the top is your injection port (usually labeled A or B). Now that you know which cord is actually controlling the injection port place this into the B (if you were using A) spot on the board. On the key pad check inj B pressure and see if it now recognizes this as installed and see if you have any controll over the pressure. If still no pressure control it really seems likely that the flow controller has gone out. This is called the proportional control valve, HP part # 19251-60720, you should be able to get this from alpha omega technologies. This page shows the diagram of the EPC unit. http://www.chem.agilent.com/Library/Sup ... a03202.pdf

On the key pad check inj B pressure and see if it now recognizes this as installed and see if you have any controll over the pressure. If still no pressure control it really seems likely that the flow controller has gone out.

Did this - no control over pressure.

This is called the proportional control valve, HP part # 19251-60720, you should be able to get this from alpha omega technologies. This page shows the diagram of the EPC unit. http://www.chem.agilent.com/Library/Sup ... a03202.pdf

Thought I'd document the removal of this valve for anyone who's curious:

The proportional control valve is behind the black cylinder (solenoid valve assembly), you can see it says "LETT KARD" of HEWLETT PACKARD on it:



This is the 5890 Series II in my chop shop that I gut for parts:



I disconnected two of the three connections easily, but the connection to the back of the inlet vent was a pain.


You have to basically unscrew the whole EPC bracket to get the proportional control valve out:



Fully removed:


Looks just like the picture, haha!

This is called the proportional control valve, HP part # 19251-60720

Earl - the one in my defective instrument is 19251-60656, the one I'm going to replace it with is 19251-60655. Is that an issue? The specs on the label are the same, and the two valves themselves don't look any different.

John

If still no pressure control it really seems likely that the flow controller has gone out. This is called the proportional control valve, HP part # 19251-60720.

Earl-

Changed the proportional control valve, and the pressure problem is still present.

Anything else I could try? Or should I try another proportional control valve? I think I have another instrument I could take one from.

Thanks,
John

The difference in the two valve part numbers should not have been a problem, but I dont know that we can rule that out entirely. Trying another one couldn't hurt but could be a waste of time.

Just curious if you have checked the settings on the main EPC board? See below for instructions from agilent site. The board switches are on the top right corner, red housing in your pics. If I remember correctly for split/splitless they are all to the right. Kind of looks right in your pic but can't really tell. What is your zero pressure reading? Set your injection port pressure to 0 then press gold key then 2 for port A, 3 for port B. If the zero reading is higher than the set point you would not have pressure control.

BTW, love the Prof. Frink on your desk!


Copied from: http://www.chem.agilent.com/Library/Sup ... a16099.pdf

Prior to troubleshooting a problem with the flow system of the GC it is prudent to check first the EPC control board configuration and the Zero on the EPC Channel.

NOTE: The EPC board is located on the right hand side of the GC within the main panel and it is plugged into the mainboard of the GC. If at this point you are unsure about how to check these switch settings, please call Agilent. DO NOT PROCEED.
The switch settings for the 5890 Series II EPC:
IN A1 OR IN B1 Right, currently unused PID
IN A0 OR IN B0 Left, Programmable Cool On Column (PID)/ Right, Purged Packed Inlet/ Right, (BPR) Split/Splitless Capillary Inlet
MODE A OR MODE B Left, (FPR) Programmable Cool On Column Inlet & Purged Packed Inlet /Right, (BPR) Split/Splitless Capillary Inlet

PID= Proportional/ Integral/ Differential heated zone
FPR= Forware Pressure Regulating mode
BPR= Back Pressure Regulating mode

Zeroing the EPC channel is necessary to correct for tolerances of the sensor and other electronic components. Zeroing the channel nullifies any offset that would keep a “0â€

Hi,
I have a similar problem, I made an analysis and during the running the GC-MS was shut down by itself and there was a message on the keypad: EPP B, I read the manual and this message corresponds to that the electronic pressure control was unable to maintain the pressure set point. I looked for a leak and I change the inlet, septum, liner O-ring and seal. I also clean the proportional control valve but now it is not working at all. Do you think that the valve was damaged? Now, the pressure set point cannot reached, and the alarm of the carrier gas started to sound and the GC-MS shut down. What can I do? how can I know if the valve is damaged?

Thanks in advance,

Carolina

[quote="karo"]Hi,
I have a similar problem, I made an analysis and during the running the GC-MS was shut down by itself and there was a message on the keypad: EPP B, I read the manual and this message corresponds to that the electronic pressure control was unable to maintain the pressure set point. I looked for a leak and I change the inlet, septum, liner O-ring and seal. I also clean the proportional control valve but now it is not working at all. Do you think that the valve was damaged? Now, the pressure set point cannot reached, and the alarm of the carrier gas started to sound and the GC-MS shut down. What can I do? how can I know if the valve is damaged?

Thanks in advance,

Carolina[check your pressure in the Helium tank make it higher by 10 psi than your highest pressure in the run, that mean if your pressure at the end of a run at the highest oven temperature is 30 psi make your helium tank pressure is 40 psi ]