Alarm system transformer + power supply (would both go bad at once?)

Dead alarm system troubleshooting advice requested ...

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Yesterday, I had been messing with the main breakers, and accidentally shut the main 200A breaker without turning off the power generator switch; so the Generac kicked in; and I heard the alarm system in the garage vehemently complaining with persistent loud beeps.

I immediately reset everything, and I thought it was all ok.

Then, today, the alarm system sounded three loud long beeps, and went totally dead.

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Troubleshooting with my Fluke after removing the alarm system external wires shows the external ELK-TRG21640 16.5VAC, 45VA power-supply transformer plugged into an outlet has an open secondary, and when plugged into an extension cord, there is no voltage from any of the three screws on the secondary windings:

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If I thought it was that simple, I'd just replace the transformer; but I wondered why the backup battery didn't run the alarm system. Testing the 12V 5AH battery out of the alarm system shows it's 13.5 volts DC (no load open circuit voltage), which, at least seems OK (I don't know how to load it though):

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So, two things must be wrong:

  1. The ELK AC transformer secondary opened up suddenly
  2. Maybe the power supply inside the alarm system box went bad suddenly
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Do you think shutting the breaker without turning off the generator could have blown the alarm system?

Any other troubleshooting suggestions?

Reply to
Danny D'Amico
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It shouldn't, but you'll never know if your experimentation somehow caused it or if it was just a coincidence. There is no question that home generators of various types have been known to screw up some electronic equipment at times.

I assume you checked for any low voltage fuses?

Reply to
trader4

Also, depending on where fuses are located, the power supply failing (for example, a shorted capacitor or diode) could have taken out the transformer secondary. So, it isn't necessarily a coincidence that both failed at once.

Pat

Reply to
Pat

If the alarm battery is more than 4 or 5 years old, there's a good chance it won't support any kind of load. They are cheap - I'd replace it.

Reply to
Arthur Conan Doyle

I don't have experience with your set up. just trying to conceive of the transient conditions leading up to the failure to better understand where to look and what to replace. Wasn't that sequence a possible scenario when your AC mains fail? Or did opening your 200A house breaker somehow supply a 'no-load' to your generac and thus you put some really high voltage places you didn't want? Or, switching back and forth did something. Or, yeah, tough, two things broke - it happens. Aren't the built-in fuse links inside those transformers in the primary, not the secondary?

Reply to
RobertMacy

Transformers often have thermal fuses inside them. But the ones I've replaced were in the primary. And since you confirmed secondary, probably not your problem. Might be worth a look tho.

Reply to
mike

Most alarm systems will beep error codes such as AC power failure and if you have a user manual, it should show you how to read the error codes from the keypad. The error codes stay in static memory until erased along with the time and date making the alarm tech's repair job a lot easier. I seem to recall that small module connected between the battery and alarm system being a battery saver that will disconnect the battery when it gets to a low enough voltage. The blue tubular looking component on the small module is an electrolytic capacitor that could be blown due to the swollen end. You can bypass the module and the alarm system should power up. It's very possible that the blown electrolytic capacitor could have shorted out and blown the fusible link inside the transformer. Try bypassing the module and see if the alarm will power up. You may be able to replace the 22 year old blue electrolytic capacitor then replace the wall wart transformer and the darned old system should work. It will operate without the module connected between the battery and alarm system. I'm assuming from looking at your pictures that you are not monitored by an alarm company and it's just a local alarm. ^_^

TDD

Reply to
The Daring Dufas

Hi, Just start with replacing the x-former and battery. I strongly suspect battery is no good. When you check the voltage did you remove a lead from battery terminal since you mentioned no load voltage. Your battery is not holding charge so when x-former quit, it couldn't supply the necessary juice.

Reply to
Tony Hwang

Look at the picture of the module between the battery and power terminals. It's a battery saver module designed to keep the battery from being completely discharged. Look closely at the blue electrolytic capacitor on the module circuit board. It looks swollen and electrolytic capacitors can dry out and become a short circuit, especially if they're

22 years old. ^_^

TDD

Reply to
The Daring Dufas

Replace the transformer. Fry's or Home Depot, off of Hamilton Ave West of Hwy 17 will be the closest location, other than some hard to find places in Campbell, to you.

Move that rat nest to the right and look at the lower right area of the circuit board. There should be a glass fuse close to where the power leads terminate on the terminal strip. This fuse might have a white casing. Pull the fuse and check it. Ohm meter will read zero if good, or 0l (zero l - Open line). If you know how to activate the continuity test of your Fluke, the tone gives a better indication since the Fluke might pick up your finger tips (it is a pain to get the leads on those little buggers) and goof ball around for a bit.

Buy some six inch long cable ties and clean that mess up. :-)

Reply to
Nightcrawler®

It's easy enough to verify that the battery is or isn't the problem. He's got 13.5V on the battery with no load. That doesnt' sound like a bad battery to me. All he has to do is measure the voltage with it connected to the alarm. If it's 12V and the alarm isn't powering up, then it's not the battery.

When you check the voltage did you remove a lead

Good grief. It's charged to 13.5 volts

Reply to
trader4

You should have roughly 16.5 V AC (maybe a little more) between the two screws marked "AC" with the wires disconnected. If you don't have that, your transformer died. These transfomers often have an internal, non- replaceable fuse; if it goes out, you replace the transformer. A local electronics shop (not Radio Shack) probably stocks them; if not you can get them online. This is a standard size; $20 plus shipping is a good price online.

Get any 12 V light bulb, except a headlight, from a car (preferably your car), disconnect the battery from the alarm system, and connect the light bulb across the battery terminals. The dome light is often easy to get to and a convenient shape. This will draw somewhere between 0.25 and 2 A from a working battery. The battery voltage under load will go down a little, but if it goes way under roughly 11.6 V, the battery is probably toast.

If the battery voltage doesn't go that far down, leave the light bulb on the battery for a few minutes, then disconnect it. Measure the battery voltage, then reconnect the battery to the alarm (with a working AC transformer connected to the alarm) and measure again. If the alarm is successfully charging the battery, the voltage will have gone up by a noticeable amount - like at least half a volt.

Alternatively, if the battery is more than about 5 years old, just replace it; it's probably bad. There may be a date code on the battery, or you may know when the alarm was installed or last serviced. Computer UPS batteries do a similar job and I can only get about 7 years tops out of them, even with the brands I like.

You have a sealed lead-acid or "gel cell" battery, and they come in several standard sizes and capacities. The label inside the door calls for a 7 Ah battery, but there is a 5 Ah battery installed in your panel; if you can confirm that the label matches the hardware, it's probably better to install a 7 Ah battery. The manufacturers are always tweaking the specs (if not the actual battery), so your size battery may be advertised as a 7 Ah, 7.2 Ah, or even 7.5 Ah. Any of these will work as long as it will fit in the panel. Also, note that the "7 Ah" size can come with 3/16" wide or 1/4" wide tab terminals; matching what you have now is best. Some 7 Ah batteries with 1/4" terminals are sold with reducers for 3/16" terminals, which also works.

I have had good luck with both Panasonic and Powersonic sealed lead-acid batteries, and bad luck with everything else I've tried, including BB Battery, UB, CSB, and Power Patrol. I'd be inclined to trust a Yuasa, based on experience with their flooded batteries, but I have no experience with their sealed lead-acid batteries. The local hardware stores carry some (look for the emergency light / EXIT sign parts), a local battery store may have them, the local electronics store will, or you can order online from Digi-Key or Mouser. I checked Amazon and a few sellers there are showing *pictures* of a Powersonic battery but probably *shipping* some junk battery. Caveat emptor.

For a 7 Ah battery online, $23 to $32 plus shipping is a good price. Locally, add $5 or so to that for shipping, plus however much the store marks it up.

When you get a new battery, write the current date in marker on the new battery and maybe on the inside of the alarm panel door.

The capacitor (that blue cylinder) on the power supply sure is an interesting shape. It shouldn't have that dent near the right end.

One test you can do: unplug W1 and W2 from the battery, unplug the wires from J1 (PWR) and J2 (GND), and unplug any other wires from that power supply. Measure the resistance between J1 and J2, and between W1 and W2. If it's less than a few hundred ohms on either reading, the power supply may be bad.

Maybe. Have you ever measured the AC line voltage in your house when the generator starts up? Does it go a lot above 120 V on either leg?

132 V (120 V + 10%) is about as high as it *should* go for a sustained period of time. If it's more than this, you have a problem. Also, try measuring each 120 V leg as you or a helper turns a heavy 120 V load, like a microwave oven, or a hair dryer or space heater on full, on and off. You should usually see a slight voltage dip under load. If the voltage goes *up* when the load is on, you might have a loose neutral, which is bad. Call an electrician or the power company.

I think you have a combination of a marginal battery and a marginal power supply (inside the alarm box). As long as AC power was on, it all sort of worked. When you interrupted and restored the AC power, the power supply or battery tried to draw too much current from the transformer, which blew the fuse in the transformer, and may have also finished off the power supply. Then, the alarm ran for as long as it could on the battery, until it shut off for low battery voltage.

If you have to hire someone to fix it, don't hire whoever did that wiring originally. It looks a mess.

Standard disclaimers apply: I don't get money or other consideration from any companies mentioned.

Matt Roberds

Reply to
mroberds

Isn't that 880 now? changes where it crosses 101.

Reply to
RobertMacy

I'm totally guessing here, but I think the transformer may have blown when you tripped the generator, and the alarm ran on batteries until they were exhausted. Then, the alarm shut down to prevent destroying the battery. Although the 13.5 V seems really high for a 12 V gel cell not being charged. So, there may be another fault, such as a shorted rectifier in the alarm panel. That would blow the transformer. But, then the panel should have run off the battery for at least a while, and in the process partially discharged the battery. So, it is a bit puzzling.

Jon

Reply to
Jon Elson

I didn't see any; but they might be there...

Still, the transformer is definitely dead.

Reply to
Danny D'Amico

I think it changes from 17 to 880 where it crosses the new 85.

Reply to
Danny D'Amico

Hmm, If some thing shorted or popped or burned, you can smell it and see it as well.

Reply to
Tony Hwang

I understand. The battery is probably at least 2 years old. And the transformer is clearly shot.

That's the funny thing. I would have expected the battery to run the system until it was dead; but the open-circuit voltage was good.

Yes. I checked the battery voltage with nothing attached, just as I had checked the transformer resistance, also with all wires removed.

I also powered the transformer with an extension cord, and checked the outputs, which were zero.

It might be that the battery was actually bad, but, it had enough juice to run the DMM (which doesn't take all that much current).

Reply to
Danny D'Amico

"Danny D'Amico"

** There must be a fuse inside that unit - wired in series with the 16.5V secondary.
** It's probably worn out .
** Open circuit testing a gell cell tells you nothing.
** The voltages on the transformer went high enough to cause a big increase in current and fuse failure, maybe something inside the alarm box failed too.
** Get a new tranny and a new battery and try them - the battery first.

... Phil

Reply to
Phil Allison

"Danny D'Amico"

** Might seem clever to crosspost and then direct all replies to one NG - but it ain't.

Cos no-body on "sci.electronics.repair" can see any replies at all.

And that is really stupid and annoying.

-----------------------------------------

.... Phil

Reply to
Phil Allison

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