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

There is a hell of a lot that you don't know. None of these give you accurate information about a capacitor.

A good tech on the scene can take meter readings, and observe things that us key board professionals won't see.

I love the term "key board professionals"!

:)

I agree. I hoping, for example, that someone knows a good way to "reset" the alarm system board, which might just be the problem.

Agreed. I see the burnt leads to the cap with my eyes; and I smelled the burnt transformer with my nose.

I agree; the best initial diagnostic is a good set of eyes going over every inch of the board!

I'm visually impaired, which means I'm very nearsighted so I use a penlight now tiny led flashlights to illuminate the circuit board which I must hold very close to my face after removing my eyeglasses in order to see what I'm doing. Some folks think it's funny to see me hold a piece of gear right up in my face. ^_^

TDD

I'm also nearsighted. Zenni Optical has been kind enough to provide me inexpensive eye glasses. I've got daily wear glasses. With some creative tweaks of the Rx, I've also gotten reading glasses which are nice for reading, or for working on the soldering, grinder, etc. Good to have some plastic in front of my eyes.

Don't rely on eyeglasses as safety devices. I just had a pair break. About 25% of a lens broke off, leaving a nice sharp point and two sharp edges on both pieces. Fortunately the glasses went the other way and I didn't get cut. The optometrist said "that can't happen", but it did. They replaced them without an issue, though.

So, you would give your friend a price on *your* cell phone without any intention of selling it? Do you think Bosch is your friend?

Gee, they won't violate their contract with each other. How odd.

Bosch has done no such thing. "The market" is not their parts. Buy a system from someone else, if you don't like the way they do business.

This is nothing new. I helped a friend start an alarm business back in the mid '70s. Some distributors refused to sell to the company, unless we signed a contract to spend at least $100,000 a year with them.

For two reasons, that is exactly what I would do were I to build a system of my own, from assembled parts.

1. You can't get the Bosch parts anyway, so, nobody can build their own system out of Bosch parts, and,
2. Even if I could get Bosch parts, I wouldn't build a system out of restricted parts, simply because it would be difficult to expand and repair in the future.

However, when I asked today at a few intrusion alarm places, they told me that the "reason" Bosch is restrictive is to prevent intelligent burglaries.

Hi tm,

That was a FANTASTIC explanation! You're one of the reasons why the USENET is so great! Thank you very much for that detailed explanation.

I picked up an electrolytic cap, and I will replace it, and test the battery-protection circuit out.

It failed this loaded test. So, now I know I have a bad battery and a bad transformer.

Luckily, the *new* 16.5VAC transformer arrived.

It sure tested funny:

a) Secondary output = 20VAC b) One side to ground = 3.5 Volts c) The other side to ground = 1 Volt

Anyway, the moment I plugged that transformer in, the battery charging circuit came to life at 13.6 Volts:

And, the alarm system control panel powered up & beeped (almost) normally:

With the battery in, or out, it gave the following error: *ALL ON, SYSTEM TROUBLE*

And, when I tried to read the error, it merely said: *CALL FOR SERVICE*

I'm not sure how to get the actual service problem, but, I am pretty sure it's the battery now that the new transformer is in place.

So, I'll google for a good source of batteries online. (Any suggestions or are they all essentially the same?)

Now that the alarm system is (almost) fixed, I can spend the effort to look more closely at this D135A battery protection circuit. resource.boschsecurity.com/documents/Data_sheet_enUS_2548187915.pdf resource.boschsecurity.com/documents/Installation_Guide_enUS_2548185099.pdf

Even though nobody will tell you a price, I found this Bosch price list on the web:

The D135A retails for $22.56 according to that spreadsheet.

:)

Hi Tony, The new power transformer solved (almost) all the problems!

As soon as it arrived, I tested its output voltage (20 VAC), which within the expected range:

The voltage from the secondary to the ground (middle screw) was weird (see picture where it's 3.5 volts on one side, and

1 volt on the other), which was wholly unexpected, but, probably not important.

Even so, the moment I plugged in the power transformer, the D2212B circuit and the control panels came to life. There is 13.6V at the battery terminals without the battery plugged in.

I think, in the end, the only things that were bad were:

1. The transformer secondary blew out
2. The D135A capacitor seems to have been overheated
3. The battery is apparently bad

Luckily, all those are easy to fix!

I'm not sure *how* to read what the control panel is trying to tell me since it only says "Call for Service", but, I'm pretty sure it's trying to tell me the (bad) battery isn't connected.

Since the D135A is to protect the battery, I assumed it's not actually *required* for operation.

So, I concentrated first, and foremost on replacing the AC power supply.

Luckily, that worked!

Sort of ...

My next step is to replace the battery.

If I were a repair technician, I'd have all these parts in stock, but I don't, so, it takes me a while to get them from the manufacturer.

PS: The application calls for a 12V, 5AH to 7 AH gel cell. Assuming I get something in that range, are they all pretty much alike, or are there caveats to buying these gel cells?

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.

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 I=45/16.5, 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?

Not weird at all. The ground is electrically isolated from the secondary of the transformer. What you are seeing is phantom readings.

Thanks for the confirmation. I have no experience with this type of transformer. I wonder why they even have the center lug, but, maybe it's for other applications.

If I were a technician, it wouldn't have taken this long to get a replacement transformer, so I would have been at this stage within the first hour had I a new one in stock.

The 12V 5AH battery also appears to be low, so, I'll get a new one on the net. The one thing I'm worried about is the terminal sizes.

In car batteries, the "series" determines if the battery will fit (e.g., terminals on the side, or on the top, etc.).

But I'm not sure *how* one scopes out prospective gel cells. For example, here's an ELK which looks like it should fit:

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.