Multi-kilovolt DC power supply... Where to start? - Page 1
Forum section: electronics / projects

author: jimdeane
author_rank: Regular Contributor
timestamp: September 03, 2015, 06:03:44 am
content: I need a H.v. power supply for some plasma physics experiments and demos. It needs to have an output range of at least 50v-2000v, at a max of about 10ma. I would prefer to be axle to adjust voltage and have an adjustable current limit.I've thought about using a Cockroft-Walton H.v. amplifier, but I'm not sure how to calculate maximum current capability of the system. I also don't know how stable the output is, I might want to run at a threshold value and wouldn't want the voltage to be varying widely with time. This would potentially run at maximum voltage and current indefinitely.If you could point me in a direction, I'm eager to learn. If I'm barking up the wrong tree with the C-W idea, please let me know.

author: Berni
author_rank: Super Contributor
timestamp: September 03, 2015, 07:56:46 am
content: What you probably want is a neon sign transformer plugged in to a variac. They will give you up to 10 to 15kV and are designed to current limit them self to about 5 to 50mA even when shorted out. This is a good solution if your priority is current limiting since the output voltage of these transformers will not be very stable when the load on it changes. They are designed to do that so that they can provide a fairly constant current at a wide range of voltages.If you really want a proper lab like supply where you can exactly dial in the current and voltage and have it regulate it within under 1% then you probably need to build your own switchmode converter. Wind a high voltage coil with a few 1000 turns and put it on a ferite core then drive a 10 turn coil using a mosfet thats driven by PWM from some regulator circuit that monitors the output voltage and current.But whatever you do be careful with these voltages, introducing capacitors to them CAN make them lethal!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 03, 2015, 08:06:17 am
content: NSTs aren't ideal as they are centre-grounded, though you could use a half-wave rectifier.They are also not designed for continuous operation at their open-circuit voltage, and insulation can break down over time.High frequency is the way to go so you don't need big caps for smoothing. e.g. flyback converter, maybe with a CW doubler on the output.For current limiting, do it on the primary side - much easier!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 03, 2015, 08:08:09 am
content: Take a look on ebay for electrophoresis power supplies - these are typically adjustable for voltage, current and power and in the sort of range you are looking for.

author: Marco
author_rank: Super Contributor
timestamp: September 03, 2015, 08:57:26 am
content: This is near the range of PMT power supplies (slightly higher power). There's a lot of designs for them using a linear regulator to modulate the input voltage of a CCFL inverter with a subsequent multiplier.PS. for primary side current limiting you might need some inductance on the secondary side so it doesn't arc before it kicks in.

author: eneuro
author_rank: Super Contributor
timestamp: September 03, 2015, 09:28:40 am
content: Quote from: mikeselectricstuff on September 03, 2015, 08:06:17 amYep, I've made some research and looked for ignition coil datasheets, where we can find that output voltages 20kV and ~1:100 ratio between transformer primary (200 turns or so) and secondary-it outputs from 12V battery current still dangereous at the levels of 100mA.Not sure but maybe they have builtin HV diodes to dump oscilations and allow high frequency ignition, eg. in a car with engine speed 3000 RPM?I wonder, if we provide lets say 100mA input 12V high frequency to such ignition car coil primary, than we should get from turn ratio ~1mA HV output current?The same what about reusing MOT transformer with the same precautions-very small primary current, so at 1:100 ratio 100mA primary should be quite safe (unless we have HV capacitor which can accumulate those small currents and create dangereus current levels HV) , since we get only 1mA at output in the case of good magnetic coupling?

author: MagicSmoker
author_rank: Super Contributor
timestamp: September 03, 2015, 11:50:00 am
content: Quote from: mikeselectricstuff on September 03, 2015, 08:08:09 amI strongly second this recommendation. Definitely the best/cheapest/easiest route to go. I bought a Fisher "FB 600" off of ebay a few years ago for around $100 while I was looking for something else because I could resist getting a 4kV/200mA max CC/CV/CP power supply for so cheap (NB - looks like they are going for $150 these days - still a bargain)! That said, I have actually used it to non-destructively test the breakdown/avalanche voltage of abused but seemingly-still-functional power semiconductors, so a win all the way around.

author: helius
author_rank: Super Contributor
timestamp: September 03, 2015, 12:19:21 pm
content: Are electrophoresis HV leads a standard item? I tried searching for them and didn't get anywhere.

author: vindoline
author_rank: Unknown
timestamp: September 03, 2015, 12:24:20 pm
content: Occasionally used HV Power Designs supplies come up on eBay at reasonable prices. I have two 3K10B's that I got for under $100 shipped. They ooooze quality. These are high end lab grade supplies typically used in nuclear physics labs. If you see one with a high price, try a lowball offer. It worked for me

author: vindoline
author_rank: Unknown
timestamp: September 03, 2015, 12:48:55 pm
content: Quote from: Marco on September 03, 2015, 08:57:26 amThis is an excellent low cost solution. For example I've tested the attached circuit and it works well for it's intended use, powering photomultiplier tubes. I don't know if it will source 10 mA or not, DIY PMT setups are generally pretty low current - under 1 mA. I'm pretty sure most (or all) of the DIY Geiger counter HV supplies will NOT be able to source the amount of current you need. Most Geiger tubes use uA of current.One thing to watch out for in DIY PMT and Geiger supplies is that you can't measure the HV with a regular DMM. The 10 Meg input impedance is much too low in this case and the meter will load down the circuit and give a false low reading. Have fun!

author: MagicSmoker
author_rank: Super Contributor
timestamp: September 03, 2015, 12:53:14 pm
content: Quote from: helius on September 03, 2015, 12:19:21 pmThe FB 600 uses standard female banana jacks for the output.

author: Marco
author_rank: Super Contributor
timestamp: September 03, 2015, 01:48:09 pm
content: Quote from: eneuro on September 03, 2015, 09:28:40 amOnly problem is that they are autotransformers, better to use CRT flybacks for the isolation (as actual flybacks, not for a Royer with the multiplier diodes removed/blown).

author: eneuro
author_rank: Super Contributor
timestamp: September 03, 2015, 07:02:37 pm
content: Quote from: Marco on September 03, 2015, 01:48:09 pmI've already salvaged one (FB-694) from Mag CRT monitor or something older (not sure) and trying to figureout howto connect this thing to eg. ZVS flyback driver ?What is purpose of those three wires turned 2-3 times over bead ferrite and this black one turn over FB main core I guess?Bottom PCB looks like this (I didn't desoldered it yet).Tried find any connection from bottom PCB ground to this main HV thick red wire, but noway-maybe didn't broke PCB bottom insulaltion with multimeter probeHowever, it looks like it is quite tricky to find flyback secondary ground and maybe this method will work from video below?Flyback Driver Completely From Television TutorialUpdate: Probbaly more complete video and... a few cm nice blue plasmaGoogle says nothing about FB-694-we'll see after desoldering this thing from PCB, however there is GND1 description on bottom PCb shown above, so maybe only more tricky way needed to verify this FB secondary GND

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 03, 2015, 07:32:42 pm
content: Quote from: MagicSmoker on September 03, 2015, 12:53:14 pmsome do have interlocks - I once spent an afternoon fautltfinding one only to find the plug I used wasn't quite the right shape to enable the interlock on the socket.And BTW don't forgetTHESE THINGS CAN KILL YOU

author: eneuro
author_rank: Super Contributor
timestamp: September 03, 2015, 09:58:37 pm
content: Quote from: mikeselectricstuff on September 03, 2015, 07:32:42 pmIt looks like Marx generators with choosen very small capacitors (pF ?) and a few kV PSU limited to lets say 0.1mA very low capacity output might be an option for HV experiments, when we know what we are doing, since we can get huge output voltage, adjust switchng frequency (output current? ) but when we switch off power source than the only power available during discharge will be from energy stored in those those tiny capacitors (this can be calculated), but we have to remember that they are at high voltage, so how to figure out what can be safe capacitance at lets say 10kV-100kV?Maybe academic experiments could help... by estiamting amount of charge stored onVan de Graaff generator metal balls like in those high school experiments?Electrostatic Potential and Electric Energy | 8.02 Electricity and Magnetism (Walter Lewin)Or something else-use human body capacitance as some estiamtion of capacitance acceptable, but of course not for very HV...Yep, it is quite complicated stuff, but human body is charged and discharged when we touch door many times and sparks happen, so... it is a lot of kV for sure....Maybe @T3sl4co1l have some interesting theory behind this, howto estimate those HV caps capacitance to get safe discharge levels when someone touches such Marx generator output by accident?What about assume safe energy levels, then calculate capacitance at given HV from 1/2*C*V^2, so when we connect in bad case sceanario where human body at 300 Ohm resistance shorts such HV cap, claculate time in which it will discharge those HV caps, so we can calculate discharge currents and timeThan recalculate for better case 1000 Ohm resistance.Kitchen ignition toys are also available.... with decent sparks... maybe teardown of those things could be interesting, while they at least should be designed to do not kill anyone?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 03, 2015, 10:02:09 pm
content: Marx gens are only good for producing impulses

author: jimdeane
author_rank: Regular Contributor
timestamp: September 03, 2015, 10:20:41 pm
content: Some very good ideas here, thanks. I hadn't thought of electrophoresis supplies, I'll have to see what comes up. The cheapest new commercial supply I found is from a British company and would be around $300. Since the grant funding dried up, I'm trying to do this on a much more limited budget.

author: eneuro
author_rank: Super Contributor
timestamp: September 03, 2015, 10:27:18 pm
content: I mean that Marx generators can be maybe easier to control-when we stop running input AC, we can estimate amount of energy, so we can store in bigger output capacitor calculated amount of energy based on how many AC pulses were allowed from last discharge.So, many impulses at high frequency stored in output capacitor can be discharged later, so it can be some kind of HV PSU... and dangerous too, when many small pulses will be stored in bigger HV capacitor for longer period of time...Anyway wiki says:https://en.wikipedia.org/wiki/Body_capacitanceQuoteOf course it will depend on environment, but.. lets try calculate for Marx generator 10 stages of 100pF each at 10kV and what energy levels we get at 100kV or better put it into spice?

author: Someone
author_rank: Super Contributor
timestamp: September 04, 2015, 04:00:37 am
content: Quote from: eneuro on September 03, 2015, 09:58:37 pmThe various international 61010 standards have limits for safe capacitance in high voltage equipment, just the connected cabling can make a system dangerous.

author: dexters_lab
author_rank: Unknown
timestamp: September 04, 2015, 08:01:35 am
content: Quote from: jimdeane on September 03, 2015, 10:20:41 pmthere should be plenty on ebay, they wont always be listed as electrophoresis supplies though, better to search for the brand names and the model 'range' name.There is a recyclers near me that regulary has them for sale and usually sell for less then £50, i would have bought one by now but i am trying to finish some projects at the moment rather than starting new ones!

author: Marco
author_rank: Super Contributor
timestamp: September 04, 2015, 11:07:02 am
content: Quote from: eneuro on September 03, 2015, 07:02:37 pmRoyer ZVS is good at getting a lot of Watts out of it, which is why the people who like big arcs use it.For a low power regulated supply I'd use actual flyback though, can be regulated much easier, has less stored energy and is less likely to kill you.

author: eneuro
author_rank: Super Contributor
timestamp: September 04, 2015, 12:59:06 pm
content: Quote from: Marco on September 04, 2015, 11:07:02 amI've simulated in simple circuit simulator one of such ZVS drivers used by folks playing with plasma generated using FBs and I've already did my custom version of this thing-soldering today etched double layer PCB shown in other threadNow desoldered PCB from this CRT monitor FB-694 and trying to figureout pinout,which is not easy, since when probed with multimeter it doesn't fit to descriptions from YT videos -I've resistance below 1 Ohm on all connected pins and I've no idea what primary or secondary could beAnyway, I think, I will do it in different way: I will add 10 turns around flyback core and connect 100kHz-400kHz 5VAC at low current ~100mAmax and I will solder two LEDs in antiparallel configuration to HV wires salvaged from this thing (main red one is rated 40KVDC based on description on it), to short output current, so I think it could be good for testing HV output current-if such trafo willthose leds due to too high current it will mean it is not safe anymore.Thinking only which can be minimum If current at which typical 3mm green/yellow LED willfail, but it is easy to test it with variable PSU and resistorDatasheets says about 20mA-30mA typical If, but probably no chance to survive 100mA or even less 50mA or so for lets say 1 hour test?This will not be of course any safety testing tool, but just estiamtion what current level is present in transformer secondary AC (HV) output without touching anything or probing with HV scope etc.-just see if anti-parelled LEDs fail or not while it clamps voltage and short-circuitBTW: My plan is reuse this quite nice FB ferrite core to make custom transformer with a few turns on primary and thick secondary to provide HV high frequency low current component to help ignite arc in transformer welder, so testing those FB pins is only for fun just to see if those 3mm LEDs will surrvive HV assuming they will clamp this HV AC voltage in both directions at low current-it shoule be below 10mA from tranforemer estimated ratios

author: Morgoroth
author_rank: Regular Contributor
timestamp: September 04, 2015, 01:37:35 pm
content: old tv and microwave transformers works well to start, the first one comes with diode, anyway to control the volage level you must control the charge in primary inductance, and thats mean pwm at 50% at some frecuency with some mosfet and cheap arduino.the simulation in ltspice is ready in 5 mins and show what I'm talking about.carefull with this things, take away all yours rf stuffs, I burn my expensivebluetooth keyboard playing with this.

author: eneuro
author_rank: Super Contributor
timestamp: September 04, 2015, 03:36:26 pm
content: Quote from: Morgoroth on September 04, 2015, 01:37:35 pmATTiny85 probably cheaper than arduinoHowever, it doesn't matter if we use push-pull or full-wave DC-DC, but did you used FB oryginal primary windings or custom and what was switching frequency?I have no data about this FB core ferromagnetic properties, so even if I know its dimensions, no way to calculate any flux, etcI've added 10T as shown below on FB core and driven this thing with ~4VAC at 400kHz using low current h-bridge via 54 Ohm series resistance (2 x 27R) and 2x 100nF ceramic caps.No sparks, so far but using my HV LEDs tester shown above it looks like pins 1-2 are shorted (no light from LEDs) and the same for 7-8, but they have resistance close to short-circuit.LEDs had ligth maximum between pins 3-6, and the same but lower light beetween (1-2)-3 and (1-2)-6, so it looks like it might FB primary coils.NOTE: I've connected now this "HV tester" to my full-wave ~4VAC "SMPS" directly (2x27R and 2x100nF) in series and... of course those LEDs @ 400kHz are notburned, so a very little input current it is-theya not even bright-similar light was on FB primary coilThe only way to get any light between main red thick HV wire (0) were between (1-2) pins and light was significant low (probably less than 1mA equivalent-no supprise if there were 1:100 or more ratio between my 10T and this FB HV output coil), so it looks like pins (1-2) might be ground, while on PCB there were screws visible, however.... no sparks of course due to very limited input current and not great magnetic coupling of this added 10T to FB coreBTW: I've tested the same LEds tester with random ferrite core with similar 8T primary and ~20T secondary and LEDs output similar not too much light @ 400kHz using such current limited "SMPS", so probably will try also connect now to FB internal primary (to pins 3-6 where I've got greatest light response), but maybe someone knows those FB has splited this internal primary to be able drive it in push-pull mode during normal operation in CRT monitor/TV ?

author: bktemp
author_rank: Super Contributor
timestamp: September 04, 2015, 03:55:50 pm
content: Look at the PCB where the big transistor originally was connected. From the spacing between the pins my guess is pin 1 and 2 is the primary.If you are wondering about the multiple connections to the anode, here is a typical schematic of a flyback transformer:http://www.hrdiemen.com/reparation/flyback/scheme/8951Depending on the actual type the capacitor and the resistors can have seperate pins or all share the same gnd pin.The white and gray wire are probably F1 and F2.If the resistor has a seperate pin, it can be used for a voltage divider for feedback.

author: eneuro
author_rank: Super Contributor
timestamp: September 04, 2015, 06:43:57 pm
content: Quote from: bktemp on September 04, 2015, 03:55:50 pmUnfortunatelly, I've cut part of PCB with FB, so I will have to recreate PCB from small pieces, while during desoldering FB from PCB I had to smash it into piecesI see no light on pins 1-2 (it can be due to very low current, or canceled induced EMF in its windings-not sure how dots looks like for this coil ), but I forgot mention that those three wires (white and red rated at 20kVDC) are energized to decent level, when powered my new 10T coil with this 400kHZ low current 4VAC-it might those F1, F2?I'm not sure if this FB was fine, while those monitors stopped working there must have been some reason that it was recycled and I do not remember if there were any display responseAnyway, thanks to this schematics-I'll try find another one to compare, maybe one of them fits this FB.I've ~0.8 Ohm between pin 2-3 and 2-6, than 0.5 Ohm between 3-6, but maybe his cheapy multimeter gives strange results below 1 Ohm-I've 0.3 Ohm between 1-2.It is strange I had no response between 1-2 when powerered with this external 10T coil, while any random bead ferrite toroid easy powers up LEDs in my full-wave SMPS setupYep, messing without schematics with HV capable stuff is not the best way to go, so probably I will salvage this FB ferrite core and build custom transformer.It looks like, providing more imput power o external 10T coil and creating arc should help find HV ground easier, but... wanted do it in more sophisticated way, but so many useless pins in this FBSimple Flyback Driver - Step by Step Instructionshttps://www.youtube.com/watch?feature=player_detailpage&v=0jWpQ8HEYgk#t=150Yep, brute force method looks fine, but of course no way to hold this HV wire in hand and messing with those FB pins, even if we know that this main red wire is 40kVDC rated in oryginal design, but there... those folks are using custom drivers so.... sometimes this insulation maybe too thin, however this HV voltage is floating in this case, but...just in case... no plans to hold in hand this wire at more powerfull driver like this

author: bktemp
author_rank: Super Contributor
timestamp: September 04, 2015, 07:15:09 pm
content: The original primary winding has the best coupling to the secondary, but to get 30kV output it needs around 1200Vpp. Therefore it may not be the best choice when driven by a mosfet.All other windings have a much worse coupling to the secondary. They are only useable for low power (less than 10W) because of the higher losses.Destroying the PCB without documenting the connections was a bad idea.Use the continuity tester to find the windings. There are typically 2-4 different windings. One is the primary, somtetimes with an additional tap. There is least one winding with multiple tabs, because they were used to generate additional voltages. In most cases none of them is connected to the high voltage section.There is only a single source for FB schematics:http://www.hrdiemen.com/They have replacement transformers including schematics for almost every TV FB, but only a few VGA monitors. Your type is available, but without a schematic.Your transformer seems to be from a larger, more expensive monitor. The 3 additional wires are most likely F1, F2, G2. It maybe has dynamic focus. That means F1 or F2 have an capacitor connected to an amplifier and modulating the focus voltage during horizontal and vertical scan.The pins 12, 13, 14 are not connected to the transformer itself but to the voltage dividers for F1, F2, G2 and maybe for the dynamic focus input.

author: eneuro
author_rank: Super Contributor
timestamp: September 04, 2015, 07:45:53 pm
content: Quote from: bktemp on September 04, 2015, 07:15:09 pmHopefully, I've found this page and method with additional 24V PSU to make happy cheapy multimeter and find this secondary ground pinHow to find the primary and the secundary coils of a FlyBack transformerHowever, they are talking about polarity of primary coil?QuoteI thought, it is classic coil aka transformer which can be energized with AC... so this primary in FB can not be driven by AC in full-wave converter?But ok, it is FB, so it is as it, I guess.Anyway, it looks like there are those HV diodes in secondary, so what about using it as input to Marx voltage multiplier where AC voltage need to be aplied?Howto multiply FB output, when we have those HV diodes on secondary side? Maybe somehing like pulse method used in the case of MPUs to get from 3.3V easy above 5V low current?

author: bktemp
author_rank: Super Contributor
timestamp: September 04, 2015, 09:35:09 pm
content: Quote from: eneuro on September 04, 2015, 07:45:53 pmIt is a flyback transformer witht buildin diodes, so the polarity of the primary winding is important:Normally it is driven using ~100V DC switched onto the primary using the large transistor on the heatsink next to the transformer. The turns ratio is about 30:1, so the 100V generate -3kV at the secondary winding. When the transistor turns off, a large voltage of ~1kV is induced in the primary and +30kV in the secondary winding.When the output is at +30kV, the diodes have to block only 30V + 3kV = 33kV. When reversing the polarity or using a square or sinewave to drive the primary (like a royer ZVS converter), a negative voltage of the same polarity as the output voltage is generated and the diodes have to block 30kV +30kV = 60kV and can therefore fail if driven to higher voltage. But the diodes are heavily overrated (there are 3-6 diodes in series, each with at least 10kV blocking voltage), so its unlikely unless you are drawing several 100W at the output or generating >50kV.Any decent driving circuit uses the flyback method, because the transformer is designed for such a circuit.QuoteA Marx generator needs a DC input voltage. A Cockcroft–Walton multiplier needs an AC input. If you want to drive a Cockcroft–Walton multiplier, this transformer is the wrong choice. Try to find an older flyback from a TV:https://en.wikipedia.org/wiki/Flyback_transformerThe "old style flyback transformer" has no diodes and works great when driven by a royer ZVS converter up to >100W.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 04, 2015, 10:18:38 pm
content: This is more than enough,YMMV whether you want to wind a transformer or whatever, though.Tim

author: eneuro
author_rank: Super Contributor
timestamp: September 04, 2015, 10:27:49 pm
content: Quote from: bktemp on September 04, 2015, 09:35:09 pmThanks, it allowed me make epic win and.... finaly find this secondary ground I hopeI've tried first linked above method with additional 24VDC PSU, but I've got only 200mV reading on this GND (11) pin, but it was largest response from all those pinsAnyway, I turned again my 400kHz PSU and powered my added 10T windings, than... checked again with my HV LEDs probe main HV output with all those bottom FB pins and... bingo.. at darker room conditions I've noticed that there is output from 11th pin and which is more important... ONLY one diode shines and it was green, while it was designed this way that whe we connect on eof wires marked with red to (+) VDC terminal, then green diode shines.So, I've discovered hidden feature of this HV anti-parallel LEDs current deetctorNow, there is no question about it it pin 11 must be this FB ground, but of course created sparks will be better for clear evidence, so lets do it, but not today.I've removed all those three F1,F2,G1 wires and resused one of them (white) rated at 20kVDC as secondary groundI was looking for ~10kV output from this thing, and AC could be better, eg. for WC.Need review Marx, because I thought it is similar to WC...However, by adding custom primary and driven as full-wave (or push-pull with split 10T to 2x 5T like a few folks did for ZVS driver) maybe I will get HV pulses if there is no output capacitor inside this FB after HV diodes and we'll be able multiply VDC pulses, not by using WC, but different method like tricky one this used in microcontroler (Dickson) voltage doubler?

author: Morgoroth
author_rank: Regular Contributor
timestamp: September 05, 2015, 04:24:57 am
content: Quote from: eneuro on September 04, 2015, 03:36:26 pmyes, but harder to debug at begginning, once you are sure about the correct ferecuency and other stuffs you can program your ATTiny, even you can program your arduino to change frecuency by serial port commands and test the best one.QuoteI used an original FB winding, I didn't have the details of that transformer and start to test until get my sparks. I dont remember the frecuency, sorry, but I found it testing with arduino as I commented before.QuoteNo need to, you can do this without calculations if you know the current limit of your FB and found the correct frecuency, now if you want a serious stuff, better build your own tesla coil, or buy a new one with datasheet on ebay, there is a huge amount of documentation on google about that.Quote400KHz is too much to get only sparks, you will only make more difficult all, start at low frecuency and try bigger ones, at some point sparks will be there, beacuse you dont have the calculations required to choose the perfect frecuency you could be switching too fast and will be no sparksbtw, for nice sparks you need 10KV for cm, more or less.and again, take away all your RF stuffs... I mean, phone, keyboards, bluetooth... at least 1m away.M

author: eneuro
author_rank: Super Contributor
timestamp: September 05, 2015, 07:43:56 am
content: Quote from: Morgoroth on September 05, 2015, 04:24:57 amThis frequency was choosen for 10T external primary and to debug this FB at low input current doesn't matter-it could be 100kHz too.My goal is not make sparks directly from this FB, but add additional voltage multiplies and when I've put into circuit simulator 10kVDC pulses in Dickson voltage multiplier configuration I've nice HV build up, eg. in 7 stages 70kV.However this voltage multiplier has some disadvantage-it needs caps rated at this rising voltage, so we had o put in series seven 10kV capable to have at output 70kV, etc.Diods could be 10kV capable, since it looked like potentials difference was only 10kV, but I need put it into software, generatespicemodel for given number of stages and then generate from software PCB with all pads needed to solder caps and prepare to epoxy or something else...Paraffin wax, which good electric insulator, but it also absorbs a lot of heat during its phase state changes in temperatures between solid and liquid stageAt such voltages probably everything should be immersed in... maybe mineral oil or.. parafin wax and everything filled in vacum to avoid any gas discharges?Parafina is quite interesting since it could be easy heat everything connect vaccum pump remove air and then let it cool back to room temperature.FB bottom insualtion I was planning to use hot glue, but maybe something else will be better? Again parafin? Parafin has quit elow melt temperature startung at 37*DEC, so not a great solution, while this Fb can heat up-maybe hot glue, to avoid any air gas discharges?I want cut all pins, but leave of course secondary gorund and only pins 1 and 2 which might be FB primary-didn't checked this yet, since I'm more interested in external split winding for ZVS driver with two mosfets...i will play woth ZVS driver today, but maybe better option will be energize external coil with 230VAC limited current in full-wave H-bridge, to be able get 10kVDC pulses from this thing.What could be transformer ration in this CRT monitor FB.. 1:100 or more?In this tableNPL: Electrical insulating materialsparafin wax looks like has higher insulation than glass?Maybe worth to try?Cheap and easy to maintainance-bottom of FB could be also immersed in parafina, so even if it melts it still be inside parafina

author: bktemp
author_rank: Super Contributor
timestamp: September 05, 2015, 07:59:53 am
content: Quote from: eneuro on September 04, 2015, 10:27:49 pmAlmost every monitor FB has a capacitor, you can clearly see it next to pin 14 (the large round bump in the case)When applying a voltage there could be sparks between some of the pins at the bottom for a short time, because the capacitor GND pin may not be the same pin as the secondary GND pin an the resistor GND pin. After the capacitor is beeing charged, it will hold the high voltage for some time whent not connected to resistor. So be carefull and short all pins together before touching them!

author: eneuro
author_rank: Super Contributor
timestamp: September 05, 2015, 06:26:09 pm
content: Quote from: bktemp on September 05, 2015, 07:59:53 amI've cut all pins on the bottom, but secondary GND and pins 1 and 2 (primary), then sealed with 5mm latyer of hot glue to avoid any air gas discharges, so this is not insulation itself, just anti sparks protection, but also no chance to directly touch any of those cut FB pins.However, what about possible RC time constant in secondary output HV stage -main red (+) HV wire capacitor shown in scheamtics you linked a few posts ago ?What could be estimated this output capacitance and parallel resistor?Update: Nevermind, looked again at this schematics and it looks like this capacitor and resistor and not gounded with secondary, but another pin which I hope I've already cut, so maybe hopefully there will be no output capacitance?I hope, I've choosen good pin for secondary ground, while now there is no chance choose another one for seconday groundI'd like to put this scondary tospiceand try estimate output current on Nth Dickson voltage multiplier stage (eg. 10th 100kV) , loaded by 300 Ohm resistor and assuming that each rising stage capacitor is created by connected in series 10kV caps, so the higher the voltage, the capacitance will go lower (thanks to series connection).It will be interesting to see amount of energy stored in each rising voltage multiplier stage-of course it can be estimated withoutspice

author: eneuro
author_rank: Super Contributor
timestamp: September 07, 2015, 04:47:48 pm
content: Finally, splited this flyback external primary, so I've three connectors which will allow drive this thing using custom ZVS driver and full-wave H-bridge or push-pull converter using rectified 230VAC mains with current limited and then we'll see if we get decent output voltage limited by a few milimeters spark gap between a few cm metal ballsI've removed its oryginal primary pins too and protected bottom using hot glue, since I couldn't got decent response on FB HV output when connected to 100kHz low current 5VAC between pins 1-2.So, here it is my HV DC PSU trafo ready to connect to driver and tune its HV output to get those test LEDs more bright at the level of 10mA or so, but of course we'll try to make some test 10mm sparks too during testing, however it will not be its normal operation mode as 10kV DC low current <10mA pulses source for Dickson voltage multiplier

author: eneuro
author_rank: Super Contributor
timestamp: September 25, 2015, 12:53:13 pm
content: Quote from: eneuro on September 07, 2015, 04:47:48 pmYep, today I had a time for some fun to test my ZVS driver designed in circuit simulator to drive this salvaged CRt monitor flyback.I've got decent a few milimeter plasma sparks at only ~23W input powerZVS flyback driver high voltage plasma from 12V car batteryWhen no arc ignited this ZVS circuit draws only 1.4W from 12V car starter battery, so quite niceZVS driver installed to flyback custom a few turns primary as close as posible to ZVS IRFZ44N mosfets drains: