5890 injection zone fan + mainboard failure

[aidnai]

Hi everyone,
I wanted to share a recent learning experience.

A while back, I was checking flows on my trusty 5890 series II when I heard something, looked up and saw two puffs of smoke, one from the injection zone cooling fan and one from the mainboard. It was purely coincidence that I was working on/looking at the GC when it happened; it was not coincidence at all that there were two puffs of smoke.

I'll spare you the pain of researching what happened (actually a topic on this forum gave me a big hint) -- essentially, a sleeve in the fan slipped, the fan blades came loose and lodged in the fan casing, which caused the motor to stop almost instantly. That caused a current spike which fried a DIP on the mainboard -- the DIP was a high voltage driver used to directly power the 24VDC fan.

The DIP that was damaged had a visible hairline fracture surrounded by a very small amount of gooey residue... the damage was hard to see without a flashlight and magnifying glass.

The DIP also had some role in running the injection zone heat (and maybe the detector heated zone? I can't remember for sure...), so the GC was rendered unusable...

Although in our case, the cost of downtime prevented me from really exploring all possible solutions (we ended up using our service contract and replacing the whole mainboard), I did later find a generic version of the DIP available for purchase.

The HP part number of the DIP that got fried was HP1820-2273. According to this crosslist reference of HP part numbers, the part is also known by the generic part number UDN2981A, produced by Sprague Elect. Co. Semiconductor Div. in Concord NH. The part is easy to find online for a few dollars -- made me very sad when I realized how inexpensive this episode COULD have been.

To prevent this happening again -- I have heard from multiple sources that the fan is not critical and can be left unplugged, but we installed a 1/4 amp fuse in the fan power (after replacing the fan of course).

If you have a 5890 and don't want to go through this, I suggest you disconnect or protect your injection zone fan power as soon as possible.

Hope it was helpful!
aidan

[Consumer Products Guy]

An Agilent service engineer told us about this about a decade ago, and we disconnected all ours.

[aidnai]

A decade! Wow talk about old news haha
When I talked to Agilent, the tech I talked to said he'd had something like two others call in with the same problem in the past month, so I figured there are still plenty of people out there with this problem... Also the Agilent tech had no information about which DIP was affected and was only able to suggest buying a new mainboard from the third party folks that took over 5890 parts/service... But glad you're not in any danger!