Electronic Alarms and Home Security Devices - Help: AC power loss alert

Hello,

I recently had to remove and replace my alarm control board. After replacing I keep getting the AC power loss alert even though there is voltage at the transformer and board. I replaced the battery, did a full power cycle, and it seems to "try" (trouble light intermittent) to solve the problem while the battery is charged, but the battery loses charge and the light goes on again and then it starts beeping due to loss of battery.

I did remove the transformer wires once while it was still plugged in, and got a spark when I reconnected. Could the transformer be partly damaged?

The system works. It's just the bothersome trouble light and the AC power failure code I am trying to get rid of.

Panels are DSC Classic PC1555. Main board is PC1555 50/300. Battery is upgrade 7aH rectangular.

Thanks

Check the voltage output of the transformer, if it's not 16.5vac, then you probably should have replaced the transformer as well (with DSC hardware, a motherboard failure often takes out the power supply transformer).

Thanks for the response. The load voltage fluctuates between 17.9 and 16.9 (changes every few seconds -- battery charge pulses?).

Update. Earlier today, I shut the unit down, and recharged the battery (which is new). It is coming in and out of "trouble" more often and the battery seems to be keeping charge.

I suspect that what is wrong is that the new battery is pulling too much current in charging. I am running a rectangular unit from Radio Shack (can get the number if anyone interested). My system originally used the smaller square battery. I had successfully used a rectangular on the first replacement several years ago, but it was a different brand.

BTW, Phelps just got his first Beijing gold! Woohoo!

A PC1555 will handle 7ah batteries just fine. When your transformer voltage is jumping up to 17 volts, it means that the system is not actually drawing power from the transformer (the transformer is essentially "free-wheeling").

These systems have a solid state PTC instead of fuses or circuit breakers. Could you possibly have a failing motion detector, smoke detector or other device that is drawing excess current and causing the power supply to shut down?

You may need to disconnect all of your power consuming devices and reconnect the one at a time.

That's an interesting point. When I first powered up after R&R, the motion detector was triggering for no reason.

I have a smaller battery now(5aH - got it before your post). No difference. The motion is disconnected, and except for the constant indication that it is hitting there is no difference. I have two control panels, so I will try disconnecting one of them next.

Will be offline for a couple of days. Thanks for the debug help.

I have disconnected each active device (IR, two keypads) one at a time. No affect. The system starts just fine and within a minute the trouble light goes on indicating power failure. It is intermittent at first though.

Using Occam's razer, the only thing that remains is that you purchased a defective board. It looks like the 12volt regulated power circuits on the board are cutting in and out. No easy fix for that.

This is, of course, based on the information provided.

MrRonFL, I concur with your deduction. My thought is I fried the board during the R&R process. I was coming to the same conclusion.

BTW, ever heard of the Transputer?

Thanks for your help debugging this!!