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Marx Generator Kits - FREE Kits for Evaluation!

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Electra

Wed Jan 30 2013, 02:07AM

Registered Member #816 Joined: Sun Jun 03 2007, 07:29PM
Location:
Posts: 156

HB, To be fair 18v may be to low an input voltage for a reliable test, if the voltage difference between each stage and the next, is that of across the preceding stageâ€™s capacitor less the voltage drops of the diodes. As you go up the ladder due to the high number of stages the percentage loss out of a lower voltage becomes larger. At 100â€™s volts per stage it becomes almost insignificant

The current also gets less the more stages there are, so any loading has a greater effect. If this is a problem this can be offset somewhat by using increasing higher value capacitances for the stages as they get nearer the bottom.

Eastern volts research has done a nice job of the boards, and Iâ€™m sure has worked everything out correctly. Diodes can fail in peculiar ways and pass some current rather than go completely open or short circuit, which can not be obvious to detect at first.

If it wasnâ€™t for me being in the UK makes me wish Iâ€™d requested one, but appreciate the hassle and cost with the postage.

Physics Junkie

Wed Jan 30 2013, 03:56AM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

So far the only things I would suggest be made differently are:

1) Thicker Traces, You can sort of see the traces under the solder mask. My opinion is that they are quite thin for high voltages.
2) Higher capacitance for each cap on the multiplier, as Electra pointed out.. thank you.
3) Some sort of solder pad or mount for utilization of improved spark gaps.
4) Xenon or Neon light indicator at the input on the Marx generator. I've seen some other marx generators that use the straight xenon tubes and it flashes when the caps are fully charged/first spark gap fires. It would also be a good way to indicate whether or not the caps are charging.

Wed Jan 30 2013, 04:57AM

Registered Member #4146 Joined: Tue Oct 18 2011, 02:01AM
Location: Wisconsin, U.S.A
Posts: 56

Don't get me wrong i know EVR does good work. I don't think its the boards. I was first running this from my variac and i couldn't even get a spark to jump from just the multiplier at 125 AC input. My thought is that i have a bad diode somewhere and i have gotten a random bad part before even when new. So in no way am i blaming EVR as others have gotten it working.

As for the trace missing it was an easy fix and i doubt it was anyones fault things just happen and can't always be perfect. I agree with you Electra about the diodes my guess is one of them is bad and thanks for the input on the testing i just found it odd that it goes up just fine for the first 5 stages and then declines and stays same voltage for the rest of the stages.

Physics Junkie

Wed Jan 30 2013, 05:24AM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

I too just discovered no trace between cap 14 and 16 on mine.

HV Enthusiast

Wed Jan 30 2013, 01:21PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Aha! Great works guys! Missing trace. That would explain why my board here isn't working either! Well, thats why there is beta testing! Appreciate the work and effort. You'll all get new boards / kits when I do the revisions after these are testing.

I should be able to build mine up today.

Thanks again!

Allison

Shrad

Wed Jan 30 2013, 01:35PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

cant wait to get it in the mailbox!

I hope it will be nice for the TE nitrogen laser cartridge I want to run

Wed Jan 30 2013, 07:16PM

Registered Member #4146 Joined: Tue Oct 18 2011, 02:01AM
Location: Wisconsin, U.S.A
Posts: 56

Glad to be of service EVR I'd be happy to test for you anytime!

Physics Junkie

Wed Jan 30 2013, 07:49PM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

EasternVoltageResearch wrote ...

Missing trace. That would explain why my board here isn't working either!

Well, I thought so too. But there is still some sort of problem with the marx caps not charging fully. When I bring the output spark gaps a few mm apart I get corona and the caps get drained, which is no good. They are charging but it seems not enough to fire. This could be because of the following:
1) need more capacitance
2) may also be a missing trace on the marx board
3) Rb may need to be different value.

HV Enthusiast

Thu Jan 31 2013, 12:26AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

I wonder if its the capacitors. These are new caps that were selected - different from the ones i used on the prototype. I will upload datasheet.

Alex M

Thu Jan 31 2013, 12:48AM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

My kit is working great, will post some video footage and photos when I get back.

I will say this though, the spark gaps are VERY sensitive and need to be just right to fire at the same time.

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