Magnet wire for coil-winding, HV cable

Bill Beaty
(Skip down for magnet wire, Wire Gauge, also high-voltage cable)

HV Diodes

One good source for High Voltage Rectifiers is... Old Microwave Ovens! These typically contain a 7.5KV to 15KV diode at fairly high amperage ( 1/3 amp or higher). Follow the usual safety precautions during disassembly of course, same as you would when messing with TV sets and tube-type amplifiers. Hint: some ovens hide their diodes within the can of the high voltage filter capacitor. Those cans are full of dielectric oil, so sawing them open can be messy.

Some electronics suppliers now sell replacement oven diodes, so high-current, hi-volt diodes are no longer that rare. Check out your local seller of TV repair parts (ECG, NTE, etc. replacement lines).

All Electronics has incredibly low prices on 200mA, 6KV rectifiers, $0.50 (# R6000)


UX-FOB 8KV 500mA 40nS ultra-fast

HVR-1X3 12KV 500mA Vf=11v (HVCA)
HVR-1X4 10KV 500mA Vf=11v (HVCA)

CL01-12 12KV 350mA Vf=12V
2CL2FL 15KV 100mA Vf=26V 100nS ultra-fast (EDI) (220mA oil)
2CL2FM 20KV 100mA Vf=35V 100nS ultra-fast (EDI) (220mA oil)
2CL2F 8KV 100mA Vf=10V (EDI) (220mA oil)

Also try microwave repair suppliers, such as Some surplus companies such as Nebraska Surplus Sales carry high-current HV rectifiers for radio transmitters.

See popular replacements NTE517, NTE541, NTE542, NTE 548

Another source of diodes is old CRT computer monitors, however these diodes are usually only rated for 50mA or less. There is always a HV diode in series with the HV connection to the "rubber cup" against the side of the CRT tube. However, often the diode is cast inside the plastic block which holds the HV transformer secondary coil (flyback transformer.) While their current is low, these diodes usually have a higher rating for reverse voltage (sometimes as high as 100KV for large screen CRTs.)

Also note that Surplus Sales has some rare High Voltage Connectors, also try Ultravolt


Where can you find thin-gauge copper wire cheap?

Odd Wire Sources

A creative scrounger can avoid buying new wire. Think OPEN-FRAME SOLENOIDS from surplus junk shops! A typical 12-volt or 24v DC solenoid may contain up to a half-pound of #30 wire costing two or three dollars. Note that some solenoids are nearly impossible to open, while others pop apart after bending with a screwdriver or some vise-grips. So if you're going to buy twenty of them for their wire, it's wise to first buy a single one to tear apart.

Also think power transformers! Power transformers and small AC shaded-pole motors. If you obtain an old power transformer or small AC motor, sometimes you can pry a couple of laminations free using pliers and a knife, and the whole stack will then easily disassemble. You're left with a spool full of wire for free. Besides power transformers, larger "choke" coils are also a source of free wire. For thin wire, try finding a transformer with a high voltage secondary such as those used in old tube-type equipment.

I've heard that you can take apart OLD CAR ALTERNATORS and obtain coils of wire. Might not be very thin wire though.

Another possibility: neon sign transformers can be disassembled by carefully heating them in an oven to melt the tar. Be warned that this is a fire hazard, and can also fill your kitchen with nasty fumes. (Try sealing the transformer inside a bag of crimped aluminum foil.) Others suggest tearing off the steel case, then chipping apart the tar using a chisel or screwdriver. I personally haven't taken any "neons" apart, and don't know if their wire size is appropriate for tesla coils. If you want to make some long hot sparks, usually #24 gauge or larger wire is best for your big Tesla coil secondary. I suspect that the secondary of a neon transformer contains far thinner wire, maybe too thin for a good TC secondary, but perhaps the transformer's primary coil can be salvaged. NOTE: sometimes you can repair a "dead" neon sign transformer without disassembly by melting its tar. Dead ones are had for free from certain neon sign shops, while new ones are extremely expensive.

One final source of wire: Mail-order surplus companies. These companies often sell damaged 10 lbs spools of electromagnet wire. Even a slight ding in the spool will cause an automatic coil-winding machine to tangle, so "damaged" wire is often not really damaged at all. Over the last few years the price has been around $40 - $60. But a 10lb spool will last you a lifetime. (Perhaps offwind it onto other spools and sell to other TC hobbyists?) Here's a table for: AWG, American Wire Gauge

Wire Suppliers

For full price, Allied Electronics carries 1lb and 5lb spools, but it's NOT cheap. A good price for wire is around $8 per pound, not $30 per pound! http://www.alliedelec.com

Also try otherpower.com, quite large spools in their products section.

Also Electronix Express for 1/4lb and 1 lb spools

Also Action Electronics for tiny spools, or 1/4lb or 1/2lb

Also Vetco for 1/2 lb spools

In the UK Brocott has spools 250G through 10KG

Or search google for +"magnet wire" +spools, or try an eBay search

Electronics Goldmine sometimes carries lots of sizes of 9lb spools and smaller.
They also usually have open-frame DC solenoids for $3-$4

Another big company which has been friendly to individuals in the past is:

161 Rodeo Dr.
Edgewood NY 11717
http://www. weicowire .com/magnetwire contents. htm

And for tiny quantities, Radio Shack sells a kit of three tiny spools, #278-1345, $4.99, 200ft of #30, 75ft of #26, and 40ft of #22


The high-voltage wire sold for use in test-leads is usually rated at 2,000V or 5,000V and is fairly inexpensive from the usual electronics suppliers. But most Tesla Coils use Neon Sign Transformers up to 30KV (with 45KV peaks)

For a quick source of short lengths of high-voltage wire, get yourself some coaxial cable, carefully strip off the black jacket, then remove the copper braid and any aluminum foil. If the white plastic inner insulation is the translucent type, and is fairly difficult to cut, then it's "solid polyethelene" and good for many tens of kilovolts. Avoid using the coax with the easily-cut spongy foam insulation, since it has a much lower breakdown voltage. If your voltage is above 20KV, use the much thicker core taken from RG-8 cable (it's nearly 1/2" diameter!)

Also call around to local neon sign shops. They might sell you shorter lengths of wire good for 10KV and above.

Note: the absolute voltage rating of HV cable is determined by the volts-per-cm breakdown rating of the plastic. Manufacturers assume that your cable will be up against grounded metal, so the entire voltage will be impressed across the thin plastic layer. This means that you can GREATLY increase the breakdown voltage of any HV cable by suspending it well away from any metal parts, especially avoiding sharp-edged metal. Tall, inexpensive cable-supporting insulators can be made using cable ties and scraps of acrylic or polyethelene. If extremely HV cable must pass near sharp-edged metal, coat the sharp edges with a thick bead of RTV silicone glue, or perhaps cover them with split hoses made of black conductive rubber. Also FYI: when the voltage is extremely high, the individual copper strands inside the cable can begin producing corona discharge, and this tends to slowly convert plastic into conductive carbon, leading to eventual HV arcing through the plastic. Manufacturers get around this problem by covering the bumpy copper strands with a smooth layer of black conductive plastic. The smooth layer is "less sharp" than the bare metal strands, so it suppresses corona. (Where e-fields are concerned, sometimes the best "shield" is a conductor!) If you strip the insulation off a 30KV HV cable and find that the metal is coated with a thin rubbery black layer, now you know why.

Rolls of HV wire can be had from various suppliers:

Also: HV Connectors, MHV and eBay, try Ultravolt for Alden high-voltage connectors

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