Electronic Alarms and Home Security Devices - DSC Classic - No power again

I have DSC Classic in the garage. It started beeping one night and decided to take a look the next day. In the morning, the LED panel was off and no response. I tested the backup battery and it was drained so low.

So what I did is buy a brand new battery, inserted it and still no LED panel functions. Then I measured the output of the transformer and it seems like it wasn't working. So i went out and bought a new transformer with the same voltage and current rating of course. Installed it, wham, my alarm system was up again.

It's working fine for 2 days and now this morning, the LED panel has no power again. I have not have time to diagnose the problem but should my alarm still work even w/o a backup battery assuming the AC power is there?

I'm thinking there is something definitely faulty in the circuitry that eventually strains and damages the transformer.

Any insights on where I should look? Tonight I plan to take apart the whole circuitry and test all components and do a visual inspection.

your battery will keep the alarm up and running until it drains out. that's what it's for. i hope you kept your old battery because it sounds like it will be okay. as far as your transformer goes not sure what would make them go like that. have you had the wiring in the garage checked? maybe it's spiking. good luck.

The issue could well be with your house wiring. The way to tell is to see whether the transformer is failing on the primary or secondary side (High or Low voltage).

That said, DSC panels are known to have catastrophic internal power supply failures under some circumstances.

Here is an update. I took off the new transformer and tested it with my DMM, it still gives me the 16VAC so I think I'm still good but it was damn hot.

I removed the electronic circuitry completely and started an electrical inspection component by component. I made sure the voltages biasing resistors to the regulator were fine.

This is where I powered the unit through my transformer w/o a battery connected. That's when I found, the input to the LM317 was very low so I suspected the diode bridge rectifier. I removed the part and sure enough, one of the 4 diodes are shorted after testing it.

That explains why batteries got drained and the output voltage was not at 16VDC.

So guys, I'm gonna go get myself a replacement rectifier and I hope that fixes everything.

I'm just curious, I think maybe when the diode first blew, it could have spiked and blew my original transformer. Transformers are pretty rugged and I think I'm lucky my new one is still working. The busted transformer measures an OPEN circuit when you should measure low resistance.

Thanks for the help and suggestions anyways. I'll keep you guys posted.

Yes, a failure in the power supply in DSC panels will often feed back a current spike that kills the transformer. It's a not uncommon failure mode (which is why I rarely install DSC hardware here in lightning prone N. FL...)

You are more ambitious than I am. I would simply replace the MB, but if you are willing and able to do the component replacement, have at...

It's been a few days and it's all good. Voltages and panel has power without problems. I confirmed the bridge diode as the faulty part.