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----- Original Message -----

From: Siggi

To: [email protected]

Sent: Sunday, October 28, 2018 11:51 AM

Subject: [HP-Agilent-Keysight-equipment] HP 8643A IO board fault

Hey y'all,

I turned on my HP 8643A the other day, and it came up with an error code 15.022.116, which implicates the I/O board. This finally motivated me to pull it down from the rack and replace it with the HP 8665A I'd acquired some months ago. The 8665A is heavy, definitely a two person lift to get it to eye level.

Now, I just started tearing into the 8643A, my fear was the backup battery on the CPU board had leaked, but it's just fine.

The instrument checks all point the same way, and I've isolated this as far as the built-in diagnostics will take it.

In initial spelunking the thing I found curious is that the?+5V on the IO board is at ~4.7V. This goes through a R40, a 1Ohm resistor, to local decoupling, and this resistor is dropping about 0.5V. So the IO board is using about 500mA, which seems high. I have the CLIP from Artek, which has full schematics for the alleged culprit.

I suspect I'll find something on the board has started current-hogging off the 5V rail, but I'm damned if I know how to hunt it down. Maybe I can borrow an infrared camera and see what's getting hot, though the hog's only consuming 2.5W in the limit.

Have you all been inside one of those or it's brethren? Any common failures that I should look out for?

Siggi