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Leaking Upper Buffer Chamber - Another Experience.

David F. Bishop bishop at msvax.mssm.edu
Sun Mar 31 15:33:23 EST 1996

Dear Autosequencing People,

Just a week ago I read Bruce Roe's description of and solution for the ABI
377 upper buffer chamber leak problem which results in bubbling up of the
coating on the front cooling plate.  This week, we found a tiny bubble on
the front cooling plate of our 6 month old 377.  The next day, the run was
truncated due to loss of current (and buffer) and there were three large
(1" diameter) bubbles on the plate.

-So, as per Bruce's discussion, I hied myself hither to a local auto supply
store and bought a tube of silicone instant gasket material.  The store had
several varieties, all silicone, resistant to high temperatures (700 deg C)
and quick-drying.  I chose a tube labled "Red RTV Silicone - Hi Temp -
Instant Gasket" part #80726 made by ProSeal (Rancho Cucamonga, CA and
Essex, England) costing about $3.50.  I modified Bruce's instructions only
slightly as follows:

The white silicone gasket was pulled out of the channel in the upper buffer
chamber (it was held in place by silicone glue) and the channel was filled
half-way with the red silicone rubber.  The red color helps visibility and
indicates where cleanup is needed (easier before it dries).  I bent a piece
of thin metal into a rectangular channel (-i_i- ) which fit into the grove
and had a lip to maintain a constant leves of about half the original
depth.  Wearing a disposable glove, I pulled this tool through the channel
to push out the excess silicone and leave a flat surface.  Work quickly, as
the compound "skins" in about 5 min.  I cleaned the area with a KimWipe
wrapped around a flat surface and placed the chamber in a 37 deg C oven to
cure for 1 hour.  I then laid a thin bead of white Silicone II Bathroom Tub
& Tile Sealent (General Electric Co., Stock # GE281 P-0391B) on top of the
red silicone.  This was smoothed out with a gloved finger and then the
original gasket was laid back into the channel with the old silicone glue
side down into the channel (that side was flat - this is why the square
cross-section smoothing tool).  The original gasket was pressed in and the
excess white silicone removed with KimWipes.  Some care is needed here to
make sure the gasket is seated uniformly.  Within 5-10 min, the chamber was
mounted on the glass plates and the sequencing run started.

The next day there were absolutely no leaks and no bubbled up plate.  ABI
had visited us the day before and replaced the front plate, but the chamber
itself is backordered for 2 weeks.  I'll probably modify the new one when
it comes.

So thanks Bruce for your timely information!

Just goes to show that we should not hesitate to report our experiences.
Most likely others are having the same experiences.

In this spirit, I note that the original upper buffer lid was too wide and
often hit the comb when it was closed.  I sanded it down to solve the
problem, and a replacement lid we just received is now narrower and does
not have this problem.


David F. Bishop, Ph.D.                   | EMail:bishop at msvax.mssm.edu
Dept. of Human Genetics, Box 1203        |
Mount Sinai School of Medicine           | Phone: (212) 241-6946
5th Avenue and 100th Street, NY,NY 10029 | FAX:   (212) 360-1809

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