HP-5890 repair tip

[heathtech]

More than once I have seen trouble with the "heated zones" on the 5890 GC. An error indicates that there is trouble and the red light flashes. I am sure others have seen this and wound up replacing the inlet fan, only to find that the motherboard no longer works. Being as it is that 5890 parts are hard to come by, I have been repairing the motherboards with success. What is actually occuring is that the inlet fan bearings go bad, causing the fan motor to lock up. This in turn causes a current spike that fries an integrated chip on the motherboard. This chip's HP part number is 1820-2273. Some of you may have realized this and contacted Agilent Life Sciences and gotten the "obsolete" response. TIP: go to THIS url. It links to another division of Agilent where the chip can be obtained.
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[Les]

If you are worried about the fan, or you begin to see or HEAR any noise from that fan, put a fuse in line and protect that mother board. Looks like the inlet cooling fan was an after thought for agilent engineers. Don't look back with 20/20 hindsight after hearing a grinding noise from the fan and say... "Why oh why didn't I put a fuse on that fan."
Only from experience do I know these things.....