Electronic Alarms and Home Security Devices - Siren alarms with keypad lockout and system freeze with DSC PC5010 (Focus32)

I was wondering if I could ask for some help or advice regarding a problem with my system. I'm stumped and so is ADT.

I have a DSC PC5010 Power 832 (ADT branded as FocusD32) with the LCD5501Z keypad as the primary keypad at the main door, and the PC5508 keypad in our bedroom.

3 times in the last year, the system has randomly tiggered the siren in the middle of the night. (The system was armed as STAY MODE). The triggering of the siren is immediate without any intial long keypad beep, as if a NON-entry/exit door/window was breached. While the siren sounds, the PC5508 keypad is completely blank, and the LCD5501Z keypad only has the trouble led on solid (everything else competely blank). Both keypads are frozen and no input is allowed. This goes on for 5 minutes. Siren is constant, not intermittent.

When the system does finally stop the siren, the trouble light turns off, and the system returns to "normal" as armed. No trouble light, and a *6 doesn't show any trouble codes. THe system proceeds to place the data call to ADT to log the event.

ADT indicates the event as "Extension Module Failure". No error number, nothing. Apparently it's a somewhat generic error, but is the same error all 3 times.

The system is about 4 years old, although the wiring in the house is about 9 years old (was originally wired to a DSC1555). The majority of the contacts are wired, but there are 4 wireless units (2 window contacts, 1 smoke alarm and 1 motion detector). My ADT plan includes the battery plan, so I actually refresh all batteries (including main system backup battery) once a year. System is tested every 3-4 months and passes every time.

ADT has been here 3 times, they check every contact, look at the history buffer, checked the wires at main unit and keypad, they've re-wired power and balanced it for keypads and motions, reset modules, but the system tests fine.

Now that this has happened 3 times, I've asked ADT to come and completely replace the main board, which they have agreed to do.

I like DSC equipment, and would be surprised if the board was really shot, but just wondering if anyone had any experience similar to this? I'm not sure what else to do, these systems are so simple. Bad transformer? (The system gets power from a transformer mounted to the electrical panel directly...no buzz coming from the transformer, and is barely warm to the touch).

Thanks everyone for any help. Sorry for the long winded post, wanted to give as much info as possible as I've described it to a bunch of techs and they all wanted this kind of info as the problem seems somewhat unique, at least to ADT ;-)

Thanks,
Downtown Canada (Humming to the tune of the DSC siren)

That's probably "expansion module failure". On a DSC, this includes things like the wireless receiver, and the keypads. I suspect that one of your keypads either has bad wiring, or the keypad unit itself is failing.

It is common (and required for a UL spec system) for the siren to sound on expansion module trouble.

It could be a failing power supply, since both keypads are blanking out on you. DSC panels are known to fail in some rather odd ways, especially where power is concerned.

We had a similar instance where a grage model became wet and caused a system wide bus error.

This subsequently shut down all monitoring panels....
(Actually looked like they were losing power).

I would definately look at a power supply as a potential problem area.