Marx Gen Help

[bremer3771]

For the past few days I have been trying to build a small scale Marx generator, but for the life of me I cannot get it to work. I am using an oil furnace igniter as the power source, I understand that it is an AC power source so I have soldered four diodes together in the proper bridge rectifier configuration. I also have a comercial bridge rectifier but it is only rated for 1kv. Pic of rectifier.

 

 

The NST is rated at 12kv but is center tapped so it is 6kv? That is what I am getting from other pages anyways. My cap's are rated 12kv at 22pfd capacitance. Resistors are 2W 1Mohm, and spark gaps are made with common wire. I dont know what the problem is, but when I test the voltage on the outputs of the rectifier I am only reading around 1000 volts. This is a pic of the MG A clips.

 

 

Here is a pic of the setup, keep in mind this is not where the circuit is operated.

 

 

ANY feedback is helpful.

 

Matt

[Qfwfq]

What kind of voltmeter are you using? I wouldn't expect to get a reading unless it's a very high impedence electronic one and only briefly after each firing. You shouldn't really need that rectifier at all, the voltage across the output won't reverse, if things work right it'll be a series of peaks of the same polarity as the DC input.

 

Have you seen this?

 

Although it is possible to make a Marx generator with just an array of resistors, capacitors and spark gaps, it can be hard to make it fire reliably, as it will depend on the breakdown voltage of the spark gaps, and there can be a fine line between not firing and firing before all the capacitors are fully charged. One crude solution is to initate the breakdown of the first gap mechanically, e.g. by waving a (suitably insulated!) screwdriver between the electrodes.

A more elegent approach is to add a trigger circuit, like the one shown above.....

[bremer3771]

QFWFQ, the rectifier is for the imput to the MG. My power source is a Neon sign transformer that produces Alternating Current, there lies my problem I believe. The MG requires a DC power source, my transformer is AC. A bridge rectifier didn't seem to work. Do I need a rectifier on both posative and negative leads? I have scoured the net looking for info, but I believe that it is going to come down to individual help. Thanks

[Qfwfq]

So I guess NST meant neon sign transformer. I've never had one along with my bacon and eggs, so I couldn't get that bit and I thought you were trying to measure the output voltage. :hihi:

 

A bridge rectifier didn't seem to work. Do I need a rectifier on both posative and negative leads?

The Graetz bridge you're using ought to be fine, as long as the diodes are rated for the peak voltage (are they?), but it doesn't give you a constant voltage unless you have a suitable capacitor after it.

 

I don't know if the third lead is central, have you made measurements to compare the voltages? Now remember, the peak voltage is greater than the RMS by the root of 2 (1.414...) and it's what you'll have on the capacitor when there's no load. This way you can measure the secondary coils with a DC voltmeter.