A suggestion:  give memorabilia items for contributions in different amounts, e.g. some small nameplate for $50, insulator for $100, etc.

I would contribute!

Steve, that’s essentially what I have now. I can choose the output of one or all of my batteries in series and then the rheostat simply fine tunes the total.

I’ve been asking myself why I think I need a precise output. My rheostat is 10 ohms and I select the starting point by plugging into the battery point I want to start with, e.g. 36, 48, 60 or 72 vdc, then turning the rheostat down (lower resistance) until either I get a desired arc or something croaks elsewhere. I always turn The voltage off by cranking back on the rheostat so that the semiconductors don’t experience such a drastic turn off. A long time ago, This seemed to have helped prevent mosfet blowouts.

I’ve also thought about using lower voltage batteries in series, e.g. 6V or even lower, to give me finer adjustment.

I need to think about what’s really going on here. Maybe I’m doing something that is no longer necessary.

Stay tuned.

I’m on it, Steve, thanx.

Is a 22 amp 120v variac capable of 44 amps at 60v output?

I’ve been using large and expensive rheostats to vary the voltage to my flyback driver.  I have about run out of capacity and I’m starting to cook these things. I expect there is a solid state way to do this.

My previous experience with solid state devices around hundreds of kilovolts hasn’t been good. I assume the electrostatic field messes up the solid-state components.

The maximum voltage input will be 72 V DC and the maximum current draw will be around 60 Amps.

What kind of the devices do I need to accomplish this?

Thanx, guys!

A voltage follower, Kluge.  1:1 input:output voltage.

What did you mean by "partial circuit?"  What's missing for a follower cicuit?

You said that 1kV analog multimeters have higher input impedance than DVMs.  Is this also true of panel analog meters that have no power supply or internal circuitry?

I have an old Triplett analog multimeter.

Thanx, guys.

Kluge, you mentioned oil circulation.  My 15 stage, fully rectified CW causes a lot of turbulence in the oil.  Does this mean anything?

I put a resistor string in a polycarbonate (or may be acrylic) tube filled with mineral oil.  The bottom of the tube structure is 1/4" polycarbonate, which is sitting an a piece of 1/4" thick micarta, on a plastic roll around cart.

The resistor string totals 1G and it's across the output of a CW multiplier that's making 25" sparks.

Low and behold, there are small (<1") arcs through the oil into the polycarbonate bottom  What in the world is going on?  What could be attracting the arc?

CW Multiplier, Progress to Date

I’ve finally gotten to the point where I’m having good luck with CWs and have a moderately good understanding of the basics (haven’t yet got to working with resonance).

My best effort to date, judged by spark length, is 23” – 24.”  The multiplier should be capable of >24”, but at >23”, I get flashovers under the oil, so I can only get 23” confidently.  I'm running it in an 8" polycarbonate tube.  Now at a strong 25"  Gonna quit here and build another of opposite polarity.







It’s a 15-stage, fully rectified, using 860pF, 20kV Murata (I think) caps, and 1x or 2x 2CL2FM diodes, 2 in series at first few stages, then singles.  I’ve also used 2CL2FP and HVRL400 diodes, both of which have a higher voltage rating, but with 20kV capacitors, so far I can get by with the lower rated diodes.

Input power is 5x 12v SLA batteries thru a 1kW 14 ohm rheostat.  I always turn the device off and on by ramping down or up with the rheostat.  I was having trouble blowing diodes and guessed that sudden voltage/current changes were responsible.  Looks like I was right.

Then to an inductive heater driver that has been very reliable.  Is specifies 48vdc max input voltage, but I don’t know whether that’s OCV or load voltage.  I'm putting more than 48vdc into it. I measure load current and voltage into the driver (more on that later).

Then to homemade FB that has ~1,000 turns 28AWG secondary in four sectors on the bobbin, and 8 turns 12AWG solid primary.  This has been fairly reliable, altho I have blown a couple of secondaries.  Run in mineral oil that I cooked and evacuated.  I expect that removing one turn from the pri would give me greater output voltage.  Also, I have no gap in the ferrite core, and I have no idea what kind of ferrite it is.




A main problem has been insulating the HV (post-FB and post-CW) wiring.  I use 2-3 layers of silicone and polycarbonate tubing.

With 60vdc output from the driver at 22 Amps at the batteries, I get 23” of a LOUD, high frequency spark.  Note that I differentiate between sparks and arcs, the latter resulting from higher current (I think).  I prefer sparks.

I’m working on being able to measure the voltage out of the FB.  I can’t do that with a DVM above ~30kV due (I think) to EMF that makes the meter blank out,  so I’m trying to get an analog meter to work, using an op-amp (any thoughts here?).

Next step is to duplicate the CW and polarize it oppositely, hoping for a combined ~48”.  We’ll see.  When I try this, I'll need to decide whether it'd work better to share the single FB with both multipliers (I've done this with smaller, half-rectified CWs); or to use a second FB and share the driver with both FBs; or to have two drivers, two FBs and two multipliers.  Suggestions welcome.

Thanx for the great help I’ve gotten from so many forum members!