I recently recieved some trouble lights on my keypad indicating low battery and bell/aux fuse open. I replaced the battery. I got up in my attic to check the siren and moved a board that was simply sitting on some of the alarm system wiring. The siren immediatly started to go off. From then on, the circuit that powers the siren will not power off. I have had to disconnect the negative siren wire at the panel to keep my siren from blaring 24/7. The keypad now indicates no problems and arms and disarms normally. I have tried resetting the clock, bypassing all zones, powered down (disconnect battery and AC), and up several times and still the siren remains active. I have also double checked the wiring in the attic where the board was resting on them and no obvious pinches or shorts are evident, although I can't see how an open circuit would cause the siren circuit to be contantly energized and yet now the keypad functions completely normal. In addition, there are no obvious fuses on the board as indicated by the Control Panel Wiring Diagram. The installer code is locked out and I have not yet tried to bypass it. Has anybody encountered this sort of problem? Any help would be appreciated.

 

You said that it was a smaller board that you moved. Could that have been a siren driver card? It's possible that you might have managed to short it hot, somehow.

 

The board that I moved was a wood board, not a circuit board. Sorry, should have been more specific. Anyway, the board was resting on the wiring. I noticed that when I lifted its weight off the wiring, the siren started. When I put it back down on the wiring, the siren stopped. Now that I've completely removed the board, the siren stays on no matter what. This seems to indicate that possibly the siren circuit has been energized for a while but not wailing due to the board putting weight on the wire and possibly causing an open circuit to the siren (I'm guessing). I've tried jiggling the wires in the attic and moving them around a bit to see if I could locate a break (ie, siren stops), no luck. So if the siren has sort of "reconnected" itself, that's fine. The thing that has me stuck is the alarm circuit board wants to keep the siren on, no matter what I do with the keypad.

 

What terminals are the siren wires connected to? It almost sounds like someone connected the siren to the aux power terminals instead of to the siren output terminals.

Also, if you have no visible fuses on the main system board, you may not have a PC 1550. What does the lettering on the main IC chip in the center of the board say? Often installers will install upgrade hardware in an existing system can so that they don't have to mess with the physical wiring.

Also some sirens used a 4 conductor cable and a tamper circuit that can trigger an alarm, but you say that your keypad indicates "normal"

 

I've had this system since we bought the house about 8 years ago. No wires have ever been switch and we haven't had any trouble with it up till now. The circuit board says PC1550 Rev 11m in the upper left corner.

Main IC Chip Lettering:
DSC R3752
06000744
9827 A8

Siren wires are connected to + and - of BELL terminals. The AUX terminals also have wires connected but I don't know what they go to. With the system NOT armed, both BELL and AUX circuits are hot at about 13-14V.

The siren itself has three wires coming out of it, only two are connected.
1. Negative (connected)
2. Red for warble (connected)
3. Yellow for steady (not connected).

The connection from the circuit board to the siren is just two wires: positive and negative.

As for the fuses, the diagram for the board seems to indicate the use of typical glass and wire fuses. There are positions on the board that match with the diagram (Batt, Aux, Siren) but instead of fuses, the battery slot is blank, and both the Aux and Siren slots have a small tan retangular component that sticks up from the board connected to each end of the circuit (sorry, I'm not up on my nomenclature :P). I know what a typical resistor looks like, perhaps this is a small capacitor. They each say RQ8M Mexico. There is no voltage flowing through these components and there is not resistance between their two connections. This is probably confusing, I could send you a close up photo if that would help. Thanks for your help. I hope the info gets us closer to figuring this out.

 

You have one of the later models where they first started using the Positive Thermal Coefficient devices instead of fuses (basically a self resetting, solid-state circuit breaker).

All I can think of is to try *7 or *7 + code.

I cannot figure out _how_ the situation you describe could get this result. If you are getting constant 12v at those bell terminals, the only thing that is left is a bad board, period. This is an intriniscally simple panel, there just aren't very many operation or programming variables involved, heck, there's only 36 programming locations.

 

I would check the voltage between the Bell + and - without any wires attached to the terminals. If you have 12+ volts you definitely have a bad board. If you have little or nothing then your wiring has a problem.

Make sure your system is in the disarmed state to be sure your alarm is not actually in alarm mode and your keypad is normal.

 

Ok, I tried removing ALL wiring from the board, then connected power back to it and then only the siren wires. The siren is still on. This is only with power and the siren connected to the board. The system was in the disarmed state when I did this. After reconnecting all the wiring, I also tried doing an EEPROM reset (hard reset), and still the siren is still on. This would seem to indicate I need to replace the board.
With that in mind, do ya'll have any opinions on what the best course of action would be? Have someone come in and replace it, or buy my own controller board and keypad. I've seen some systems on the internet, which is best for the bucks?
thanks.

 

It sounds like you are fairly comfortable at this point with the technical aspects. You could fairly easily swap out the keypad(s) and control with something more modern and more capable. Take a look through the archived threads. Upgrading systems is something that comes up a lot.