Burglar alarm help please! Electronics folks?

[David Rose]

I have a 20 year old Radio Shack Safe House wired alarm on my business. It is setup for "normally closed" operation with door switches and window and door foil tapes. Shortly after we got to church tonight the alarm started going off. It reset and went off around 4 times from 6 to 10 PM.

After we got home, answered the messages from neighbors, we started searching for the problem. This one turns out to be "not so easy" to find. It is only one loop of four in the system. All wiring is exposed for easy searching.

The odd thing, and what makes it hard to find, is that when I touch any exposed contact or point on any tape in that loop, it stops showing a broken circuit. Let me better explain. I am holding a test lead. I touch ONE contact to any wire or tape in the system and the alarm stops! I am not touching the other end of the lead to anything including myself. I supose it is just induction from my body through the insulated wire that causes it to quit failing.

I have sent a note to Radio Shack, but I have no idea whether they will respond. I don't think they have carried this unit for some time.

Tonight I spent over two hours bumping wires and slamming the door and checking contacts and never got the unit to show even a flicker of a break. We did get one alarm while searching. I went over every wire and connection while the alarm light flashed. Nothing seemed to effect it. Then again, one touch of one end of the test lead to the tape very gently and it stopped.

Does anyone have any ideas or any place I might search out such a problem? I have to be home to shut the thing down before the police are called. They got 4 calls this evening. I don't want to be one to "cry wolf" until they don't listen, besides needing my sleep.

I don't know whether there is a relay for each loop or whether there is one for the whole unit. If there are separate relays, I suppose one of them could fail.?

Thanks for anything in the way of help,

David

[David Rose]

Update: we got another alarm about two hours ago. After going over everything *again*, I focused on the door for some reason. This time the alarm light kept flashing when I touched the tape. I got to try the probes on a few areas before it quit. Then when I rubbed my fingers across the bottom strip on the door, it went off a couple of times. So I stripped that tape off and retaped it. I couldn't force another alarm, but I have only been able to do that a few times. Sooo... I don't know where we truly stand, but there is hope! Boy, I hate vague problems!

I still don't know why simply touching the tape in a totally different area could cause the break to "heal".

David

[Matt Meiser]

Dave, since you basically have one giant loop, touching it may be bypassing a part of the circuit, replacing that part with you.

[David Rose]

Matt,

I could see that if I was touching two places. What lies in between the spots would be taken out of the loop. That is the way I test for bad connections. But this was just one touch in one spot with one end of the test lead. Only what was a break in the tape (in a tiny spot) would be shorted. And I touched the tape with the single probe in many different spots. I am very grateful that we had no alarms this morning and this was our day off, so sleep...

David

[Tyler Howell]

Batteries and power supply in good condition?
Contacts at alarm unit clean and tight?
Any resisitance in contacts on window and door sensors?
Vibration levels change??

[Steve Clardy]

Sounds like a case of Buglars in your Burglar system.
Loose contact somewhere

[Matt Meiser]

Ahh. I misread what you said. I thought you were holding a test lead in one hand and actually touching the tape (with your finger) with the other.

[David Rose]

Tyler,

After an hour of going over connections, I tested the battery and transformer. They checked good. I can't get to the relays without a complete teardown, so I don't know how the contacts appear. They may be solid state instead anyway. I'm not sure. Resistance is almost nil throughout the loop. Vibration did not change, but there is a lot of it in that circuit do to the door opening and closing.

David

Batteries and power supply in good condition?
Contacts at alarm unit clean and tight?
Any resisitance in contacts on window and door sensors?
Vibration levels change??

[David Rose]

I don't know about "burglars" but there sure is a bugger in there somewhere.

D

Sounds like a case of Buglars in your Burglar system.
Loose contact somewhere

[David Rose]

Oh, I got ya, Matt. No, just a single contact with the point of a test lead with nothing (but whatever conducts through the insulation from my body) on the other. Still a mystery.

David

Ahh. I misread what you said. I thought you were holding a test lead in one hand and actually touching the tape (with your finger) with the other.