sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Security, Alarms and Paging Fire-Lite 450 Fire Alarm Horn

I don't know if this question can be answered here, but I'll give it a shot.

I found a Fire-Lite fire alarm horn (Model # 450). The horn is rated for 12VDC @ 400mA and I would like to see if the thing still works.

I purchased a simple 120VAC -> 12VDC @ 1A power supply, but there are no markings anywhere on the horn to indicate which of the (2) leads is positive and which is negative.

1 lead goes to a transformer and the other lead is soldered to what looks like a switch and then on to 1 side of a radial capacitor. One side of the capacitor has a white stripe around the circumference, but the lead in question is on the opposite end.

I'm afraid that if I hook the power supply up backwards, I'll blow the capacitor. :scratch:

I tried Google, but that came up empty and there are no references to this model horn on Fire-Lite's web site.

This question may now be moot. I noticed that one of the two leads has broken off right at the body of the capacitor.

It is a Black Cat "PKM 4P47" rated for 400VDC, but I can't tell what the MFD rating is because the number is worn off.

If I can't get a wire soldered back on where the lead broke off I'll probably end up tossing the horn into the "circular file".

Dexman,
That white stripe at the end of the capacitor means that it's a "polarized" capacitor [striped end = cathode/negative side]. The lead at this end must go to ground. A polarized capacitor will not handle reverse voltages, which can result in them actually "exploding".

Is this the only capacitor on the horn? I can check with some of my local contacts at Honeywell to see if they may have some of these Firelite 450s around, maybe they can get a microfarad rating for us?

The transformer is making me wonder. If it's a DC horn, there wouldn't be a transformer, unless if it's wired in series with that one lead, like a choke/coil. The way to tell would be the transformer only has two leads, not a typical primary/secondary as a normal AC transformer.

I have seen manufactures offer the same type horn in an electronic DC version (siren) or a 70volt speaker version. I have also seen the DC rating on the tag when it is actually a speaker, not a siren. The dead give away is two same coloured leads vs. a red and black or red and white lead.

The way I would test is with a signal generator first (an audio signal). If nothing, than a 12 volt DC source. They don't normally burn out from wrong polarity if you don't leave it for a long time (been there, done that!)

A little trick on old caps, use a #4 screw and screw it into where the broken lead came off. Use this as your connection point.

Just out of curiosity what are you trying to do with the horn anyway? :shrug:

Hi everyone!

The capacitor is the only one on the unit and I haven't been able to solder a wire where the old lead broke off.

I really had no official plans for the horn, other than to hook it up to the power supply and see if it worked. The unit has been lying around for years in the workshop of the church I attend. The horn looks like the ones that were used in the elementary school I attended. Those horns used to scare the (you know what) out of me. They were loud and nasty sounding.

The former "fix-it" guy was an electrician and he left quite a bit of stuff lying around. I guess he was going to clean the shop at some point, but he passed away before he could get to it.

I was cleaning up a little bit, found the horn and though it would be nice to see if it worked. :shrug:

I like that "trick" that twisted mentioned. If I can find a screw somewhere on that mess I call my workbench, I'll give it a whirl and see what happens.

Mike, if you can find out what the rating on the capacitor is, I could always look for a similar one from another supplier (if the trick doesn't work for me). This is a "low priority" task, so there is no rush.

I would just go ahead and connect the leads to the power supply for a second to see if it sounds or not. Over the years I have reversed the polarity on many horn/strobes and none of them ever blew because of it.

If you get no sound out of it either way it may need 24 volts to operate if a jumper has been cut or removed. A lot of fire equipment is 12/24 volt switchable.

Some of the 12 volt stuff I have run across I test with the battery in my truck.... just hook one side to + and the other side to -.

Once I had a 12 volt bell I had to test and it didn't matter which wire was connected to which terminal believe it or not, it worked either way. I guess that's because the gong moved up and down no matter which way the coil was conducting.

Ok. I'm officially deaf!

I connected the power supply without connecting the broken end of the capacitor and WOW!

I'm not sure what purpose the capacitor serves, but the horn worked quite "nicely" without it.

The horn sounds just like the ones back at my elementary school when I was there. (The fire alarm system was upgraded when the school was remodeled a few years back).

I had a flashback as soon as it sounded.

Honestly, I'm glad that the sound of fire alarm horns has been refined since the 70's. This horn sounds loud and nasty!

I'd still like to replace the capacitor. :bow:

Mike, if you can find the rating, post it here so I can go to a near by electronics store (not Radio Shack) to see if they can find a suitable replacement.

Glad to HEAR it!

What? I can't hear you! :rofl:

Happy New Year Bob!