TV Spark Gaps

Dodgy Dave has got some in his lock-up on Canvey Island. Just send cash. <Splutter>

Not sure if you are talking about what we called the "exciter" cable which plugged into the back (and off to the side) of the picture tube.

If so, try a Google search of "picture tube spark gap" or cut and paste this link: http://www.google.com/search?q=tv+picture+tube+spark+gap&sourceid=ie7&rls=com.microsoft:en-us:IE-SearchBox&ie=&oe=

Hope I understood properly and this helps

Not the right part. These mounted on the pcb. Thank you

These are commonly available from most electronics stores and are called many names such as gas discharge tubes, gas tube arrestors, gas discharge tubes, etc.

Now days they are compact devices with the arc gap contained within a gas-filled sealed container for superior and repeatable protection (especially for high voltage and high power lightning and spike protection applications).

These are much more expensive than the component we used. Thank you

Well, I think I know what you might mean. Try the Mouser link below to see if it's close.

http://www.mouser.com/Search/Refine.aspx?Keyword=spark+gap

Just out of curiosity, give us a hint where you worked. Back in the day I served some time making Ye Olde Analog TV sets.

I think know what you mean. I worked on CRT's many years ago. The spark gaps we used were small glass lozenge-shaped tubes with wires on each end, sort-of like capacitors.

How about:

http://au.alibaba.com/product/252754033-SPARK-GAPS-KSA-SERIES-FOR-CRT.html

or:

http://www.rell.com/Pages/Product-End-Category.aspx?productCategory=10265

Not the component. Thank you.

The spark gap in question was extremly inexpensive, was constructed from two wires and a ceramic holder. The end to end spacing determined the spark gap. They were not mounted on the kine, they wer mounted on the pcb.

I know what you are referring to but I am not sure if they are even produced anymore. The open air gap tended to have corrosion problems and in rare occasions could ignite fine dust that tends to accumulate inside TV's.

Thats partly why the enclosed type mentioned earlier where developed.

Thank you. I suspected something like that would be the case.

Since no one has actually asked yet, what is your specific application.

Sure you can build a simple and inexpensive spark gap like the ones you mention (or even find some in a second-hand electronic junk store if you are lucky), but what are you trying to do exactly (and why do a few dollars matter unless this is for mass production).

Can you please provide more information.

These were made from 5000 volt ceramic capacitors with a small notch cut into the disc by a fine hacksaw in volume by the capacitor maker and they cost pennies and they flashed over peak voltages.

Those are the ones I remember, but there is no way the notches were cut with a hacksaw. Ceramic is way harder than any hack saw Ive seen. I suspect they were cut with fine diamond saws/slitters.

If the OP is really anxious to get one or two, I probably have a couple stashed away somewhere...

Ceramic is way harder than any hack saw Ive seen. I suspect they were cut with fine diamond saws/slitters.

I think they cut through the far softer dipped encapsulant, perhaps at some stage in the baking cycle when all you would need. Or they could use a saw when finished because the encapsulant is just a filled epoxy and easy to cut..

All they need to do is expose the edge of the ceramic wafer which has a deposited electrode on each side with the lead wires soldered to it, no need to slice into the ceramic core.?

These visible notch types are now outlawed, dust collected in the gap by electro-static attraction was ignited in a number of cases where fires came from TVs. This problem was severe in smokers houses when the tar droplets would create dust clumps that would propagate a fire easily.

They developed notched spark gap capacitors with the gap internalized = no spark in the air.

Clearly you are right that the encapsulant is much softer, but to expose the ceramic, the saw would have to at least occasionally touch the ceramic. which would rapidly dull the saw. In addition, a saw would break chips away from the encapsulant, and I remember very clean narrow cuts. Finally, the foil does not normally extend all the way to the edge of the ceramic, so some ceramic would have to be removed to expose the foil. Of course since these were special-purpose devices, they could have been made with the foil extending to the edge of the ceramic...

All this is just from having observed many of these devices in TVs and computer CRTs, a goodly number of years ago, so I may be remembering poorly. I looked briefly through my collection of capacitors, and even took the cover off one old CRT, but I didn't find any.

I don't remember hearing about the fires in smoker's houses, but it is logical.

GA: wikipedia has this:-

Less sophisticated (and much less expensive) spark gaps are made using modified ceramic capacitors; in these devices, the spark gap is simply an air gap sawn between the two lead wires that connect the capacitor to the circuit. A voltage surge causes a spark which jumps from lead wire to lead wire across the gap left by the sawing process. These low-cost devices are often used to prevent damaging arcs between the elements of the electron gun(s) within a cathode ray tube (CRT).

Thank you. Do you have a vendor?

The components I am referring to were not capacitors nor were they made from capacitors. It conscisted of two wires clamped in a ceramic holder (at least I think it was ceramic). The fire problem sounds real and is probably the reason that I have not been able to find any with the search engines. Thanks to all who helped.

Application is proprietary and the use is for mass production. I may try to build it.

Thank you

There is an adjustable spark gap tooling used by Briggs & Stratton (Lawn & Garden Care Equipment) mechanics that have 3 screws that have a conical point on each. 2 of the screws are at 180 degrees in a Phenolic ring(PCB board type meterial) insulator. This tooling is for checking the spark for the engine and is applied between the spark plug or earthed to the frame and the other screw electrode is inserted into the spark plug lead.

This should be suitable to your application if you encase it in a clear Tuff-ron(Perspec) insulating board used in manufacturing Electrical control panel boards. You can adjust the gap and the second offset screw is to control the spark to a straight line between the 180 degree opposing screws conical tips.

The Briggs & Stratton Part Number is # 19051

Go to your local Mower place and they should get this for you.

Merry Christmas to ALL

They still use them in BT termination boxes for domestic telephone (wire) they call them Lightning Arrestors have a look there. Hope this helps..

As the OP has not specified his operational requirements it is difficult to recommend a specific type. But if he needs ceramic insulation presumably the sparking is continuous there fore it is needed for heat resistance. If it is intermittent then Teflon or Tufnol would be adequate to make his own spark gap it is a simple construction.

At reasonably predictable humidity, the voltage at the arc point can be predicted. If you use some wires that do not easily corrode, you set the distance between the wires. I don't remember the voltage to distance calculation, but it's predictable enough that Machlett labs used to test very high voltage tubes with a voltmeter that was 2 metal bulbs that had a vernier and was calibrated in voltage. The plant had tons of high voltage cages everywhere with those gap-meters in them. There was value for the distance and voltage. I'm sorry I don't remember it. The TV's you're talking about had the gap caps and pc boards that simply had spaced contacts on them.