The SX recorder gets turned off after the day shift.  It's 2.5 years old.  Hasn't hickupped since it was installed.   Firmware was updated about 5-6 months ago.

Yesterday, it would not boot up when power to panel was turned on.  It got stuck on a launch screen with messages about "informing modules".   Repeated efforts to cycle power to the recorder produced the same result, stalling at the same point.

The I/O cards have green and red LEDs that are visible through holes in the side of the recorder.  The first AI card blinked red every couple seconds, whereas the the 2nd and 3rd AI cards did not. 

Took the rear panel off, removed first AI card and tried to boot.  1st time it stalled, 2nd time it black screened and the internal speaker made screeching noises, 3rd time it booted but the processor ran at about 1/100 normal speed.

With the back off, I noticed the clock battery, one of the small US quarter sized batteries (CR2032).  So I took the clock battery out for a minute, then re-installed it.

The recorder started its boot process (1st AI board still out), showed a message about clearing SRAM, and also went through a clearing of the data buffers.  But it completed the launch process and appeared to run normally.

I powered it off, re-installed the AI card, and the recorder booted normally.  The clock needed to be reset (it went back to Jan 1, 2003) and I had to get a temporary password from Honeywell's TAC phone center because all the security user accounts were locked out (probably associated with the data change).  

Something went that got fixed by cycling the clock battery.