Mike,

If you are referencing the Agilent 6890 GC with Electronic Pressure 
Control (EPC) and a split/splitless inlet, then you are correct. These 
modules can become clogged and stop working. Here is the bad news: last 
time I purchased one from Agilent, it cost $1872 (part number G1544-
60500). Furthermore Agilent does not offer depot repair of this module, 
nor are they field repairable even though some of the parts bear Agilent 
part numbers (Agilent claims they must be assembled under clean-room 
conditions). The problem seems to be the small orifices clogging with 
condensed sample/solvent (that in-line filter is pretty much worthless). A 
fast way to check your unit besides measuring the output flow rate is to 
note the pressure at a specific flow rate, say 1 cc/min then increase the 
flow rate (to say 2 cc/min) and note the pressure change on the GC's front 
panel. It should increase rapidly, overshoot only slightly and settle down 
to a stable value. A clogged unit will increase slowly, overshoot the set 
point by a lot and oscillate around the new set point sometimes never 
settling down. Hope this is of some help.

Richard A. Berger
Mass Spectrometry Resource
Washington University Medical School
Metabolism Division
660 S. Euclid Avenue
St. Louis, MO 63110
(Voice) 314-362-2602
(FAX) 314-362-8188

On Thu, 11 Aug 2005 15:35:25 -0700, Michael Kubo <[log in to unmask]> 
wrote:

>Has anyone ever replaced a faulty split flow valve on their HP 6890?  I 
have
>heard that this is one of the weak points of these GCs and it looks like
>ours finally kicked the bucket.  There is no difference in flow to the
>split/splitless vent in the back of the GC using a flow meter when 
switching
>back and forth between split and splitless mode as well as varying the 
split
>ratio in the split mode.  Any advice is greatly appreciated, especially 
any
>advice on reference materials on how to work on the guts of these
>instruments.
>
>Cheers,
>Mike
>
>
>Michael Kubo
>NASA Ames Research Center
>M/S 239-4
>Moffett Field, CA 94035
>(650) 604-6110
>
>