VTTC running on a high voltage microwave oven inverter

This is a little experiment to see if my VTTC will run using an inverter microwave oven supply rather than the heavy iron core transformer. As Tesla Coils create electrically noisy environments, I didn’t expect the inverter to function well. Initial tests are promising and I need to do more comparisons.
Thanks to ‘Tested to Destruction’ for supplying the inverter.
Note: Don’t try anything with these transformers without being fully aware of the risks. Their configuration is unusual(+ve ground), it is easy to make mistakes and end up with a very dangerous circuit.

[@peterzeboroff7448]

I am almost 60 now and I really enjoy watching your videos because it reminds me of my entire childhood. Since I was 8 years old, I was into building high voltage generators and small tesla coils. I have played around with literally thousands of old television fly backs. Now my main interest is building fairly powerful high power semiconductor and also Ruby lasers.

[@tuopeeks]

Thanks, similarly only young at heart I've always been into this stuff. The high price for big semiconductors and ruby lasers the only bar to experimenting there too. My videos are slightly randomly related to what I get hold of.

[@peterzeboroff7448]

@@tuopeeks Hi,although I have been fascinated with high voltage my entire life,Lasers have even more so but I agree the very high cost of all the various components is a very real problem,it has taken me literally 50 years to finally find a suitable Ruby Rod and the proper dielectric mirrors for the cavity.Those mirrors are even more rare than the rods.Now I have a huge issue in finding the large number of proper capacitors for the flash lamps Ebay is full of them but I don't trust them because if the amount of fake Chinese junk online.

[@prius.killer]

i stumbled across your video by searching "microwave" and sorting by upload date. not disappointed. very cool shit.

[@MVVblog]

Why this chanel is so low in subscribers? You have tons of good interesting video!!!

[@T2D.SteveArcs]

Very good mate .. my guess on the caps would be rf bypass to gnd and the diode? Maybe transient clamp incase of filament opening ???

[@robson6285]

The two diodes and two capacitors do the fullwaverectifiïng with voltage doubling. Normal MOT+1diode+1cap rectifies only halfwave but doubles voltage too. Magnetrontubes start to draw their current only above 4kV. Btw, to get positive hv you could simply have reversed both diodes. (Btw2, that cap and diode on both filamentterminals is for a more spread electronemmission over the length of the filament)

[@T2D.SteveArcs]

You need a centre tapped secondary to achieve fullwave rectification with only 2 diodes

[@T2D.SteveArcs]

And reversing the diodes wont solve because its a flyback meaning the diodes conduct when the igbt is off therefore you would also have to reverse the primary coil connections

[@michaelwall3401]

Excellent!

[@T2D.SteveArcs]

Let me know if you find out their purpose mate they only need 1 cap and 1 diode for doubler

[@DaynDickson-bw5wi]

In the video it looks like the high voltage wire goes to the Center section of the transformer

[@tuopeeks]

Output from doubler network on the MOT inverter supply to smoothing cap for tube anode in the VTTC

[@theiosog2843]

Cool vid ma dude

[@DaynDickson-bw5wi]

Please give more information on the filter you use between the transformer and Tesla coil

[@tuopeeks]

Nothing specific, just a toroidal ferrite core with about 10 turns of thick copper wire. Just to reduce HF noise either way.

[@DaynDickson-bw5wi]

i would think think this inductor or choke would cause an issue when the power is stopped as the polarity is reversed in the inductor! do you have a bypass diode on it?@@tuopeeks

[@tuopeeks]

@@DaynDickson-bw5wi Its has a tiny inductance and could be omitted. Didn't cause any issues on test. .

[@murraymadness4674]

You mentioned the stock control using a 50hz square wave..do you know the specifics? I want to swap out the old transformer with the inverter for a camper convection oven setup and want the lighter weight and ability to run it off 12v. thanks.

[@tuopeeks]

As a safety and control feature the inverter requires an external square wave input of 220Hz. The duty cycle adjusts to control power output for the magnetron. If the frequency is is too far away the inverter will just not work. Easy to use a 555 timer to create this control circuit and the inverter input is expecting a logic voltage I think I was running mine at 6V. Not sure how you want to drive the inverter from 12V as the driver is looking for full wave rectified mains. There is no smoothing and if I remember it is looking for the ripple frequency. The onboard control logic supply is low and uses a dropper resistor on the main p.c.b..

[@celticqaidbear]

Cool

[@arkohmay]

Could you drive the flyback-inverter primary coil with a ZVS driver instead of a 555 timer?

[@tuopeeks]

Don't see why not. Might be difficult to get very large currents though. The primary would need to be rewound with suitably heavy gauged wire.

[@jonlitchfield8888]

Yes ive done that, put on the usual 5+5, but the zvs was under too much strain and heated fast, and even destroyed my fets on a run. I think because the airgap in the cores of all these are huge, 6-8mm!!!

[@Electronichub_05]

I found one last year but it was blown :/

[@ketelin4285]

Well , it was the time for microwawe ovens to join the bunch of appliances which die after 2 years and 6 months ...

[@bradnowak405]

Could you detail how you switched polarity please.

[@tuopeeks]

Switching the output polarity is dangerous. Only attempt if fully aware of the issues. In this instance I removed all chassis reference connections form the positive output so this output was fully floating at the transformer. This involved removing the ferrite core ground connection and positive transformer p.c.b. connection to the board. With this done it is possible to reconnect ground to negative with reference to the positive output. A new short wire is added from the floating positive connection on the transformer to the bleed resistor to discharge the capacitors on the transformer housing. Note the bleed resistor also has to be removed from the p.c.b. at the positive end. This connection also has a high voltage wire attached as this is now the + HV wrt ground connection and there are no connections from this to any part of the p.c.b.

[@thomasguilder9288]

That‘s the proper way to do it, I‘ve seen people who tried turning the hv diodes around but that doesn’t match the way flyback transformers transfer power from primary to secondary, you would have to swap the primary connections on the flyback, too to make it work this way

[@seleseleufudu6525]

R 701 its value please

[@tuopeeks]

I have a 820R across pin 1-2 CN701 connector