Unusual behaviour DSC-864ULC

[Frank Kurz <tech@xxxxxxxxxxxxx>]

OK... This is the second call I've attended on this control.  It's less
than a year old.  The last time this happened was two months ago and the
problem had cleared by the time I'd arrived on site.  This time around
however, the AC light was "off" and the system looked to be running on
battery.

Here's the troubling part.  Voltage at the AC terminals was 16.9VAC.
Charging voltage was 13.2VDC.  Yet the panel was displaying an AC fault.
  There is no visible problem with the board.  I've downloaded the
software and checked all the relevant locations.  Panel's programmed for
60Hz, etc.  This looked to me to be a board level problem.  I
disconnected the battery (didn't touch the AC) and the system "died".  I
reconnected the battery and nothing happened.  I then disconnected the
AC and reconnected it.  Panel comes back on line (displaying the normal
clock failure trouble).  Reset the clock and the panel clears and
operates normally.

Since this is the second time the same trouble has appeared, I figured I
should replace the common control (to be on the safe side).  I swapped
the sucker out and downloaded the information from the old system to the
new one.  Everything works.  All zones annunciate.  I'm gonna take the
old MB and set it up at the office.  Anyone encountered this problem
before?  I'm thinking this could be a "hold-over" from that batch of bad
rectifiers but the strange thing is the panel is only seven months old
and the power section of the board looks to be completely normal.

Oh...  One more thing.  The station received an AC Failure signal with
the restore when I reconnected power.

Weird.


--
Frank Kurz
www.firetechs.net