Hope this is the correct place to ask this question.
I'm looking to replace the paper condenser??/resistor??/capacitor?? (not sure what it is)on my 1946 1/2 ton P.U. horn. There are no markings on the paper shell. Can anyone tell me what to replace it with?

See photo of part I need.
http://s1117.photobucket.com/albums/k583/harold146/?action=view&current=HornInside.jpg

Thanks,
Harold

Good photo Harold. I wish that I could help you but I don't know anything about these. Somebody must. Who else knows about capacitors and can make an educated guess about this?

That is a condenser that reduces the spark across the points. I would guess the value to be about .5 @ 50 WVDC. Radio Shack may have one of that or close value.

Ray,
Thanks for your reply. I will pick up one at Radio Shack & give it a try.
Harold

Some of the best local advise on this and other electronic questions can come from "aged" HAM operators. If there is a local club in your area they may be very helpful with advise and a recommendation of who could aid in a repair. Good luck, Mike

Ray,
I went to Radio Shack today & was told they do not know what the WVDC means in your reply. Was also told I need to tell them what Microfarad I need.
Any suggestions?
Thanks,
Harold

I just finished laughing for 5 minutes after reading the last three postings. But then again, it's probably only funny to an electronics or electrician kind of guy.


Harold, I went through a lot of materials last night looking for a specific answer for you. I found some good horn diagrams that listed a "capacitor".... but no value.

And trying to get "any kind of technical help" at a Radio Shack is a thing of the past. (I could tell you about my experience there two weeks ago, but I won't.)

Using Ray's info, lets just "logic" this thing out.

1. It's a 6 volt horn. Therefore you need a capacitor that is good for a few more volts than that since the "draw" is fairly large. 50 volts DC would be a reasonable way to start.

2. As someone said, the capacitor is there just to prevent the points (on the vibrator) from arcing - and burning out. So .5 microfarad would be an easy place to begin.

You're not talking about much money (I hope!!!), so buy one and try it out... they shouldn't cost more than $2... After you install it (temporarily is okay), then HONK the horn for 10 seconds.... Then do it again about 10 more times... watch for a spark at the points. You shouldn't see one (or at least not very prominent.) And feel the capacitor to see if it gets warm. If you feel ANY heat, then go with a slightly larger size.

--Everyone else, please feel free to jump in here if you have additional opinions.

And.... yes... I am a Ham.


--Bill Barker
N4BKW

It truly is a shame that Radio Shack has turned into a retail outlet and staffed by clerks. The once were HAM hangouts with nearly everyone having a RTO or HAM license. Got my first RTO (radio telephone operator) ticket in 1961 and later my HAM ticket. 73 N5VGG

WVDC= Working Voltage Direct Current

.5 = .5 Microfarad
50 = 50 volts
WVDC = Working Voltage Direct Current

Chipper
You are right about Radio Shack (Tandy down here), sadly to say many similar type stores are going the same way and us Ham guys are becoming black box operators as a result.
I got my NAOCP (Novice Amateur Operator Certificate of Proficiency) in 1984.
Tony (VK2VCR)

Bill,
I appreciate your input. I went back to Radio Shack & a real friendly teenager assisted me in looking at their display board of capacitors.
You suggested using a capacitor .5 microfarad 50 V. The smallest on the display board was a 1.0 microfarad 50
Not being an electronics person I asked my "sales" person & she shrugged her shoulders & said it's up to you. Will the 1.0 microfarad 50 V work? or should I try another source?
Thanks, Harold

Can't cost too much. Give it a try.

Harold,
For this use (ie. horn), the rating of the capacitor isn't very critical. If you drove to the store (twice, now), then you paid more in fuel than it would have cost for you to buy a couple of capacitors of different sizes.


This is an easy system to "test" or "experiment" with... In all likelihood, you won't hurt anything by trying a couple of different sizes. The frequency needed for the vibrator is not critical. A wide range of capacitor ratings should work fine.

(I am SO tempted to dig out my college books and work up an equation for this solution.... )

--Bill

Bill,
I also thought about calculating the optimum value but it would require knowing the frequency of the vibrator. Then I considered all you were trying to do was to reduce the current across the points the instant they closed to reduce the spark I got the "why bother" "have better things to do with my time" thoughts. But then there is the challenge, NAW!

Bill gave the closest thing to the right answer, but there's one more thing to consider.

It's true that the value of the capacitor is not critical. The coil of the horn is an inductor, which stores energy when current is flowing through it. When the contacts open, the stored energy has to go somewhere. I haven't seen horns with capacitors to absorb this energy; mine have wirewound resistors. But either a capacitor or resistor allows the current to circulate through it instead of in a spark across the contacts. There are many popular values that should be easy to find: 0.1, 0.22, 0.47, 0.5, 0.68 microfarads. Any of these will work. However, I think 50 V is too low. From the picture, that looks like a paper capacitor, which was rated for at least 250 V. That's what I would use, just to be on the safe side. If a voltage higher than the rated voltage is applied to the capacitor, it will fail quickly. Modern capacitors have dielectric materials much better than wax and paper (like ceramic, for example), so they are physically smaller, but they'll work just as well.