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

Page 6 of 9  
http://www.alarmhow.net/manuals/Radionics/D2212/D2212B%20Installation%20Manual.pdf
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On Sat, 23 Nov 2013 16:39:07 -0600, Nightcrawler® wrote:

That's a very nice find, especially since three things appear to have been blown when I turned the power off without turning off the generator:
1. The ELK TRG140 16.5V AC transformer secondary windings are now open 2. The D135A battery-protection board cap is apparently blown 3. The Radionics D2212B alarm circuit board is apparently malfunctioning
The test of the Radionics board was to hook the battery directly to the power and ground leads. That drew 98ma and the alarm system merely beeped an incessant single beeeeeeeeeeeeeeep for the entire time that I left the battery connected.
http://farm8.staticflickr.com/7370/11017175664_eb4f8a7d31_o.gif
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The bottom three terminals with the Green, Red, and red and black wires are the power to your external panels. Normally, the green is a data line, the black should be a negative 12 volt line and the red should be +12 volts. If someone mixed up that wiring, it could present a short circuit to the power supply and battery. You might want to go through all the mess and clean it up. A fault there could also explain the transformer failure.
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On Tue, 26 Nov 2013 01:33:21 -0500, tm wrote:

The alarm has been working for years, so, I'm pretty sure the wires didn't all of a sudden get changed.
The good news is that the new transformer arrived today.
However, the voltage output wasn't at all what I had expected from a 16.5VAC transformer secondary.
http://farm6.staticflickr.com/5532/11078019855_b27612e531_o.gif
I measured: a) 20 VAC across the secondary b) 3.54 VAC across on side of the secondary to ground c) 0.98VAC across the other side of the secondary to ground
Huh?
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That's normal. The secondary winding is floating. What voltage do you see across the aux terminals (DC)?
Is a) above with the transformer connected to the alarm board?
Get a fuse in line with the secondary to save the transformer in case something is shorted. You don't want to damage the new transformer. I would use a fuse equal to the secondary current rating marked on the transformer.
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On Tue, 26 Nov 2013 23:01:57 -0500, tm wrote:

Whew! I had expected a center-tapped transformer or something.
Thanks for setting my mind at ease on the odd voltages to the ground lead.
The 20Volts I measured is probably because the RMS voltage must be the 16.5Volts, so *that* part at least makes sense.

I measured 13.61 volts across the DC terminals with the AC transformer in place.
That seems good, to me, if a bit low for charging a 12V battery.
http://farm8.staticflickr.com/7440/11078202723_a6deb1394f_o.gif

The transformer has a PTC fuse in the secondary. But, I *do* agree with you. I'm shocked there is no fuse.
I even asked at the intrusion alarm houses I visited today. They said the board itself is protected from overloads, so, nobody bothers with a fuse.
This reminds me of the situation with garage door torsion springs where the "industry" puts in the cheapest spring saving *them* ten bucks, but if you put in your own spring, you *always* opt for the better (longer life) spring!
For me, I agree with you. I'm heading off to RadioShack or Frys to get an inline fuse holder.

It's a 16.5VAC (RMS) output, with a power of 45VA, so, given I=P/V, I get IE/16.5, where I is 2.7 Amps.
So, how does double that sound for a fuse, e.g., roughly around 5 Amps for the inline fuse for the transformer secondary?
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You will measure 16.5 volts RMS AC when the load is 45 VA.
Use a 3 amp fuse.
Can you check the current draw with your meter on AC Amps? Just for reference.
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On Wed, 27 Nov 2013 01:49:57 -0500, tm wrote:

Ah. I see. Makes sense. The voltage drops under load.

Again, makes sense. That (roughly) equals the rating.

I measured roughly 700Ma to 800Ma AC current out of the secondary winding when I powered it up and set the alarm and opened a door, etc.
http://farm6.staticflickr.com/5542/11080669443_9cb7dbacb0_o.gif
http://farm6.staticflickr.com/5493/11080670153_27483d2de9_o.gif
http://farm3.staticflickr.com/2865/11080574116_6743a084a9_o.gif
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On Wed, 27 Nov 2013 03:48:00 +0000 (UTC), Danny D'Amico

Reasonable. You tested it with no load, right?

The secondary is isolated from the primary. Any measurements made across the isolation are meaningless.
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On Wed, 27 Nov 2013 14:03:09 -0500, krw wrote:

Correct.
Also, when plugged into the alarm system, it only drew 800mA.

Thanks.
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On Sat, 23 Nov 2013 12:13:57 -0500, krw wrote:

That's exactly how I'm (trying to) handle it.
I don't have any problem replacing anything that tests bad; but, just throwing parts at a problem isn't what I'm trying to do.
Of course, that means I need to look closely at the circuit board, as that's the first step of any diagnostic procedure.
Looking at the BOTTOM of the circuit board, I find something interesting at each end of the electrolytic capacitor leads:
http://farm4.staticflickr.com/3677/11013129635_251c6ff9ec_o.gif
It almost seems as if the capacitor overheated, but, it it not an open circuit:
http://farm8.staticflickr.com/7397/11013119175_dfa5301efd_o.gif
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On 11/23/2013 1:07 PM, Danny D'Amico wrote:

It actually looks like someone has replaced that electrolytic before. Oh yea, looking at your other pictures, it now looks like the board was manufactured in 1998. ^_^
TDD
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On Sat, 23 Nov 2013 16:41:36 -0600, The Daring Dufas wrote:

There were unused leads for two batteries, so, I suspect there were two batteries in series initially. The battery in there now doesn't look all that old. The equipment was made in the 90s as you surmised.
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You should peel off the double sided tape on the LV Disconnect board and see if any track has been damaged.
tm
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On Mon, 25 Nov 2013 21:02:38 -0500, tm wrote:

Thanks for that advice. The sticky tape was covering the traces:
http://farm8.staticflickr.com/7345/11061234756_3a7bb08f86_o.gif
So, following your advice, I peeled it mostly off, and looked with a magnifying glass as you had suggested:
http://farm6.staticflickr.com/5474/11061138385_441b250d61_o.gif
The 1,000uF 35V capacitor leads are burnt a bit, but, it could have been a replacement cap for all I know, as the cap is not shorted nor is it an open (it's about 350 ohms steady).
http://farm8.staticflickr.com/7450/11061137965_035e7abf80_o.gif
However, the fact is that this sequence shows *something* is wrong with that D135A battery-protection board:
1. The battery is 13.31V
http://farm4.staticflickr.com/3780/11016175513_af16f7c34e_o.gif
2. Connecting this way is 13.31V:
http://farm4.staticflickr.com/3772/11016174693_48beeeeed8_o.gif
3. But, connecting this way is 0V:
http://farm4.staticflickr.com/3786/11016128584_20e6cba24f_o.gif
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I hope that you realize that you are not getting a reading off of the capacitor. Most likely that is the resistance of the other components on the board.
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On Mon, 25 Nov 2013 22:46:30 -0600, Nightcrawler® wrote:

I used to use a capacitance meter (I forget what we called them way back in the 80s in one of my lab classes), so, I'm familiar with the fact that it's hard to measure capacitance.
However, I did think (errantly perhaps) that the capacitor would show as a short or as an open if it were "blown".
Since it showed with resistance, I wasn't sure, what I was reading. I *did* expect the voltage to climb slowly, since the meter would have been supplying charge to the capacitor's plates; so, the fact that the resistance was steady should have been a good datapoint.
What I will likely do is take a trip to RadioShack and buy a 1,000 uF 35V electrolytic of a similar size and see if I can wire it back up.
I wanted to first draw the circuit so that I could figure out how to test it though.
So, thanks for pointing out the faux pas in my measurement. I appreciate the correction.
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Use the meter test lead (red) to touch the red battery lead to the output terminal briefly. You should hear the relay pull in. Then the power terminal should be at 12 volts. This board depends on AC power being applied to the alarm unit and some battery charging current needs to be available to arm the battery protection board.
tm
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On Mon, 25 Nov 2013 23:53:35 -0500, tm wrote:

Oh! That would make a huge difference since the AC transformer is out of commission at the moment (waiting for the replacement to arrive).
Thanks for that helpful advice!
Maybe I should only test it with the AC transformer in place?
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Just bump it with the 12 volts from the battery. That will pull in the relay and latch the output. When the voltage falls below the 9 volt limit, the relay will drop out and disconnect the battery completely.
Just for the fun of it when you go the RS, you might pick up an in line fuse (3 amp or so) and put it in the red battery lead. that will keep the fire from starting. :) Get yourself a supply of fuses just in case. I don't see any fuses on the boards at all.
When you get this working, next thing to do is disconnect all the other panels from the main unit. Tag all the wires so you know where they go. That way, you can narrow down any power issues to just the main board.
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