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Unknown Testing Apparatus/Outfit with Model T Style Buzz Coil

Jason Dahm

Subscriber
Last Subscription Date
07/12/2019
I've had this for a while but I can't seem to figure out what it is supposed to test. It has a male household plug and outlets/bulb sockets wired into it. Also some female receptacles and an automotive bulb socket. It has a cradle with two connectable leads for whatever is being tested. It utilizes a Model T style coil as can be seen and appears very "factory" built. Can anyone provide any insight?? Thanks in advance.20200102_140843.jpg20200102_140855.jpg20200102_140904.jpg20200102_140911.jpg20200102_140922.jpg20200102_140934.jpg
 

Oldtech

Subscriber
Last Subscription Date
12/14/2019
Very Curious. It may be a general purpose test unit for motor work, coils, or whatever. I only say this because my father built a similar looking setup -( minus the Model T coil), for working on motors, transformers, generators etc. You can insert resistance into a circuit using light bulbs or plug in devices to test things that would otherwise just go boom when plugged in. I've never seen a Pro built version before though.
 

Steve Dawkins

Subscriber
Last Subscription Date
07/04/2016
I found this item to be very interesting, and studied the photos for a while. Thanks Jason for providing such clear photos from all angles, and the ruler for reference. I'm still at a loss as to its purpose, and hope someone can answer that.

Assuming (and we know what can happen there...) that the 120 volt inlet plug is for the power supply input, one wire goes from it to the porcelain socket mounted inside the box. I suspect (assume) that socket is for an Edison base fuse. The other wire from the inlet plug goes to the porcelain socket on top. That may be for a light bulb that was used as a current limiter. It is wired in series with the 120 volt outlet that's located next to it. Maybe that was used to check appliances or power tools for short circuits. I remember that in the old days of fuse panels, a light bulb was screwed into a fuse holder to test a circuit that was shorted. The bulb would burn bright until the short was located and eliminated. The bulb would then go dim or out, depending on other loads connected to the circuit at that time.

I had a model T spark coil when I was in junior high school. Our electric shop teacher allowed us to order some neat things through the school. IIRC, those coils had 6 volt primaries. What I don't understand about this test instrument is how the voltage drops from 120 VAC to ~6 VDC to operate the spark coil. There appears to be a resistor of some sort inside the box, but it looks to be connected to one terminal of the spark gap, so that would be high voltage, and not part of the primary circuit for the model T spark coil.

I wondered if this instrument was used to test fluorescent lamps, considering the U bracket in the center and the leads on each end with alligator clips. I'm also curious about the function of the spark gap.

This instrument/device is really cool. I particularly like the hardware used for the spark gap, and the bakelite thumb screws used for the binding posts on the sides. I wanted to trace the wiring from the photos, but some of it is concealed by the spark coil.

Somebody please tell us what it was used for!
 

Oldtech

Subscriber
Last Subscription Date
12/14/2019
20200103_161238[1].jpg


This is the test rig my father built probably in the 1950s. Whether he just built it "out of his head" - a definite possibility, or had seen something like Jason's machine I have no idea. He used this as a glorified test light. He could put resistances in the circuit to test things that used too much current. Most of the time it was just a circuit tester,
 

Jason Dahm

Subscriber
Last Subscription Date
07/12/2019
Notice that two of the posts are labeled "armature" and "high tension"? I wonder if this is a clue...?
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Perhaps the spark coil is part of an entirely separate testing apparatus from the 120 volt stuff. A battery would then be connected to use it?

I have one of those spark coils too. It’s the ignition system for the black powder cannon that was made for my grandfather when he was a kid in the ‘20’s. One inch bore, ~18” long. BOOM.

Keith
 

Oldtech

Subscriber
Last Subscription Date
12/14/2019
Been studying this a bit. The 2 terminals on the same side as the 120V plug look like they could be dry cell connections. Doesn't help much to figger what it's for. It looks to me like the vibrator coil setup might be a separate thing. Wondered if it might be for testing telegraph circuits,
 
Last edited:

AlanR

Registered
The vibrator coil could possibly be used as a hipot tester - maybe - although without something to limit the current, it'd be a destructive test.

Alan
 

georgineer

Registered
Jason, I've made a composite view (with the underside view flipped) to help me understand it, and I still don't!


test set main.jpg
The components at top left are separate from all else, and I presume are mains voltage. It is a series circuit and goes: chassis plug - Underneath lampholder (fuse holder?) - socket outlet - top lampholder - chassis plug. The only purpose I can think of would be as a simple continuity tester. The terminals on the right hand side I think are for 12V dc. It has a similar series arrangement with a series lampholder and socket outlet, and again I can only think it would be a simple continuity tester, with the item under test connected to the socket.

There is a fair bit of wiring detail that can't be seen from the pictures, but this is my guess at what's going on: The black wire going leftwards from the lower right terminal probably goes to the switch, which I presume is a simple on-off affair to control the coil. I have no experience of trembler coils, but if it's a three-terminal one like the one in this diagram I think the switch would be connected to the common primary/secondary terminal, labelled ARMATURE.
coil2a.gif
The unlabelled middle terminal on the test box should then be the secondary (high voltage) output, externally connected to the terminal labelled HIGH TENSION and thence internally to one end of the spark gap, and also to the Terry clip. The other end of the spark gap would be connected back to the common primary/secondary terminal, though I cannot see how. I believe the cotton-braided clip lead appearing through the bottom side would also be connected to the common primary/secondary terminal. If a spark plug body was put into the Terry clip and the braided clip lead connected to its top terminal, the spark plug could be tested. If no spark plug was fitted, the spark gap would serve to protect the coil from excessive voltage. As I say, this is largely guesswork, and I don't know what the other braided clip lead is for. Any suggestions or enlightenment welcome.

My conclusion, then, is that it's some sort of combined spark plug and continuity tester. I don't believe it was a commercial product, but made by a competent amateur with bits from the come-in-handy box. If the top right components really are to be operated at mains voltage my blood runs cold at the thought of the two otherwise identical sockets next to each other, and the exposed live metalwork underneath with no evidence of a cover ever having been fitted.

Thanks for the challenge,
George
 

Lonnie Grissom

Registered
I've had this for a while but I can't seem to figure out what it is supposed to test. It has a male household plug and outlets/bulb sockets wired into it. Also some female receptacles and an automotive bulb socket. It has a cradle with two connectable leads for whatever is being tested. It utilizes a Model T style coil as can be seen and appears very "factory" built. Can anyone provide any insight?? Thanks in advance.View attachment 373941View attachment 373942View attachment 373943View attachment 373945View attachment 373946View attachment 373944
I think it is a multi tester for model t spark plug, horn, and possible other electrical components. I once owned a checker for coil , horn and spark plug. It had the magneto to generate curent and was hand cranked.
 

Owen Bosma

Subscriber
Age
78
Last Subscription Date
02/07/2018
I have a spark coil market 110 volts, I don,t remember where I got this coil, or what it was used for. It is possible that your coil is 110 V. I think the the socket inside would be for a tunger rectifier bulb.
 

Ben Cowan

Subscriber
Last Subscription Date
12/07/2019
My guess would be a multi tester but more for testing sections of armatures for opens , continuity etc. had a growler in shop where I taught high school mechanics many moons ago. Ben
 
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