Author Topic: BrOdin coil - High power Big sparks!  (Read 46145 times)

Offline Hydron

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Re: Coil destroyed at 4ms on-time.
« Reply #60 on: March 06, 2021, 08:51:06 PM »
Ouch, that's a decent scorch mark!

I second davekni's suggestion - was thinking of making the same one before I caught up to his post!

My other question would be how much would the frequency change if you just chopped off the damaged section? If the IGBTs can take it, higher frequency could actually give you some more margin on the primary primary tap position.

Finally, I'm not sure thick epoxy will help a lot - you're never going to get all the way under or between each turn, and if heating of the secondary is significant (which it may be at these power levels) then a thicker coat could actually be worse. If the issue is turn-to-turn breakdown then there may not be an easy fix beyond lower coupling or a spaced winding (which is not simple to pull off).

Offline davekni

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Re: Coil destroyed at 4ms on-time.
« Reply #61 on: March 06, 2021, 09:15:09 PM »
Good point about thermal expansion issues with thicker resin.  I think the PTFE ring was intended to limit arcing from primary to secondary.  My thought of thicker resin was an alternative way to prevent primary-to-secondary arcing.  I agree with Hydron that thicker resin doesn't help with secondary winding-to-winding breakdown.  Hopefully removing the PTFE ring will be sufficient to prevent that.

Some form of thick insulation on the inner primary winding may be another option.  There is much less issue of trapped air gap there, as there is little field along any air gap, only through its thickness.  Any corona there can't be worse than no insulation.  (My DRSSTC primary is litz wire between two polycarbonate plates with silicone RTV filling the inner diameter, with forced air cooling from below.)

Yes, shortening the secondary by removing the damaged part came to my mind too.  If you decide to scrap the existing secondary, it could be fun to experiment with the short version first.
David Knierim

Offline Hydron

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Re: Coil destroyed at 4ms on-time.
« Reply #62 on: March 06, 2021, 09:21:44 PM »
I would also be wary about thick insulation on the primary - too much and it will increase the field across the air-gap (the higher dielectric constant of the insulator means that it has less electric-field per unit distance than air, concentrating the field across the airgap). If there wasn't a primary-to-secondary arc then I'd leave the primary well enough alone (well, except for the purpose of changing the coupling).

Offline Mads Barnkob

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Re: Coil destroyed at 4ms on-time.
« Reply #63 on: March 06, 2021, 09:48:37 PM »
Its great to see you are pushing the limits and finding a few edges here and there, then go on to expand the distance to edge and keep pushing!

I would dare to say that "failure at the lower 20%" on the secondary coil is a old, but not well-known/well-explained problem. It has been described earlier by Steve Ward/Conner as a "whiplash" problem, I tried to gather as much information on it as possible in the tesla coil secondary coil article (scroll down to "Spark loading during ground strikes") and Secondary coil protection and the whiplash effect (scroll down to "Secondary coil protection and the whiplash effect") in the DRSSTC design guide.

Kizmo made a lathe rig to make a grove in the secondary form to get it spaced wound, to get a higher voltage-per-turn ratio and as far as I know he never destroyed that secondary coil...

Dr.Spark is one of the few coilers that went completely over-board with varnishing secondary coils. He would do 30-40 layers of polyurethane and sand in-between ever 5-10 layers to remove bubbles. I think he later on did some epoxy pour secondary's that almost looked like it was covered in glass. I do not think he ever destroyed a secondary coil. But on the other hand, he properly did not run the coils as hard as Kizmo, Terry, Eric Goodchild and Frederick here with his massive 4ms on-time.

Just having the coil running for so long at 3 ms is a great achievement!
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Offline davekni

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Re: Coil destroyed at 4ms on-time.
« Reply #64 on: March 06, 2021, 09:54:31 PM »
I certainly agree that too much insulation on the inner primary turn would reduce air gap significantly and thus increase field.  A smaller amount of insulation can increase the effective radius of the primary inner turn, thereby reducing peak field, besides adding insulation.
David Knierim

Offline fh89

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Re: Coil destroyed at 4ms on-time.
« Reply #65 on: March 06, 2021, 11:30:27 PM »
How symmetric is your secondary coil?  Repair may be possible if you can install it upside down.  Voltage stress is lower at the top, so may be able to handle the patches.
Unfortunately it is asymmetric. The top end winding stops 5 or so inches from the top
 

The endcaps are different too with the top one having a single threaded rod for the toroid mount and the bottom having two threaded rods for bolting to the primary. The mounting holes were hand drilled, so they probably won't line up if I swap them.


I think I'm goin to go ahead and try to splice the secondary wire and try to save it before scrapping the whole thing and starting over. The splice will be about 5" up from the primary. I might drop the coupling just a tad too to about .157

I already have the secondary coil form cleaned up pretty well.

This is the damage with all of the bad turns removed


Closeup of melted copper embedded in secondary


After some scrubbing with an acetone soaked rag


Did some scraping with a chisel to remove burned PVC and embedded copper.


Some of those chunks are really deep in there.


After sanding with 60, 100, 220 grit sandpaper




Quote
My other question would be how much would the frequency change if you just chopped off the damaged section? If the IGBTs can take it, higher frequency could actually give you some more margin on the primary primary tap position.

Finally, I'm not sure thick epoxy will help a lot - you're never going to get all the way under or between each turn, and if heating of the secondary is significant (which it may be at these power levels) then a thicker coat could actually be worse. If the issue is turn-to-turn breakdown then there may not be an easy fix beyond lower coupling or a spaced winding (which is not simple to pull off).

I had to remove just over 6" of windings, so frequency would go up quite a bit. The coupling would be way off too. I think I'm going to try to splice the wire and fix it, but rewind an inch higher to reduce coupling a bit and allow a greater primary to secondary clearance. Between this and leaving out the PTFE, I think it may be enough to allow me to properly melt my MMC instead of the secondary!


Quote
Its great to see you are pushing the limits and finding a few edges here and there, then go on to expand the distance to edge and keep pushing!
I am for sure expecting to break things pushing limits like this! Very interesting when things you are not expecting break first! Not sure when I will be happy with the performance- I would like at some point to call it a completed coil.

Quote
I would dare to say that "failure at the lower 20%" on the secondary coil is a old, but not well-known/well-explained problem. It has been described earlier by Steve Ward/Conner as a "whiplash" problem, I tried to gather as much information on it as possible in the tesla coil secondary coil article (scroll down to "Spark loading during ground strikes") and Secondary coil protection and the whiplash effect (scroll down to "Secondary coil protection and the whiplash effect") in the DRSSTC design guide.

Very interesting stuff there. My RF ground is a dedicated 8' ground rod located about 10' away from the coil. It is connected by 1" wide copper braid about 20' long. Maybe my ground is too low impedance allowing "whiplash?" Maybe I could run the coil with the breakout point pointed straight up to reduce heavy ground strikes.

Quote
Kizmo made a lathe rig to make a grove in the secondary form to get it spaced wound, to get a higher voltage-per-turn ratio and as far as I know he never destroyed that secondary coil...

Dr.Spark is one of the few coilers that went completely over-board with varnishing secondary coils. He would do 30-40 layers of polyurethane and sand in-between ever 5-10 layers to remove bubbles. I think he later on did some epoxy pour secondary's that almost looked like it was covered in glass. I do not think he ever destroyed a secondary coil. But on the other hand, he properly did not run the coils as hard as Kizmo, Terry, Eric Goodchild and Frederick here with his massive 4ms on-time.

This is some stuff to consider if I end up needing to rebuild the secondary from scratch. Maybe my repair and modifications will hold up, we will see!

Quote
I certainly agree that too much insulation on the inner primary turn would reduce air gap significantly and thus increase field.  A smaller amount of insulation can increase the effective radius of the primary inner turn, thereby reducing peak field, besides adding insulation.

There is an 1/8" thick polycarbonate disc covering the primary (the idea here was to help prevent primary strikes). This didn't help with primary-to-secondary arcing when the secondary started at the same height as the primary, but with me raising the secondary first turn height, the primary-to-secondary distance is basically doubled and this disc will now be between the primary and secondary and at least increase the creepage distance.



Offline fh89

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Re: Coil destroyed at 4ms on-time.
« Reply #66 on: March 15, 2021, 05:54:33 PM »
Update on the secondary repair:

I tried my best to do a half-lap splice on the 23g magnet wire . It took several tries to get it lined up somewhat decently, then I sanded the rough edges and tried to even it out as much as possible.


Closeup of splice:


I rewound the secondary a little higher than the primary. New k should be .155


Coated the new windings with Famowood Glaze coat epoxy:



Really not sure if this will hold up, but we will find out this weekend!

Offline davekni

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Re: Coil destroyed at 4ms on-time.
« Reply #67 on: March 15, 2021, 06:14:13 PM »
I'd say that is an impressive splice.  Good luck with testing!
David Knierim

Offline fh89

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Re: BrOdin coil; the swole DRSSTC
« Reply #68 on: March 16, 2021, 03:42:59 AM »
Quote
I'd say that is an impressive splice.  Good luck with testing!
Thanks, ha ha. It looks good to the naked eye, but the magnified view makes me nervous!

Got the coil back together. The secondary first turn is now 1.75" higher than the primary.
 

This is how the splice looks to the naked eye.


Magnified 10x



I'm not going to be surprised if this burns up almost immediately, but it only cost $30 for the 1lb spool of magnet wire to try out this repair.
« Last Edit: March 16, 2021, 03:48:10 AM by fh89 »

Offline davekni

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Re: BrOdin coil; the swole DRSSTC
« Reply #69 on: March 16, 2021, 04:32:07 AM »
Yes, I see the tight spacing.  Too late now, but I would have left an extra small gap in winding pitch on either side of the splice.  It may be OK, but could be susceptible to a turn-to-turn arc at the splice.  I suggest running low repetition rate initially, examining the splice after each test before increasing power.  If an arc forms there, you might catch it before burning all the way around the turn.  Perhaps you could remove one turn, cut out the existing splice, and form a new splice with a half-pitch added gap on each side.

Good luck!
David Knierim

Offline Hydron

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Re: BrOdin coil; the swole DRSSTC
« Reply #70 on: March 16, 2021, 10:38:34 AM »
On the other hand, if the splice works with the tight spacing then visually it looks great for a repair!

Offline fh89

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Re: BrOdin coil; the swole DRSSTC
« Reply #71 on: March 20, 2021, 08:27:02 AM »
Well guys, I fired the repaired coil up tonight and... It lives!

I built a 2x2 "Tesla Table" to get it up higher off the ground. Human for scale.




After a few brief test runs, I said f-it, we're going full send. Cranked it up to 15ms and let 'er rip.

15' foot ground strike


Another ground strike


Some streamers


Racing sparks and flashover, but coil survived!


Vid at 15ms, 10Hz. There is some weird frame-rate interpolation issue happening here with the gopro, it doesn't look this slow in real life.

Some low res phone video



I want to try it again at 3ms and 50Hz, but that dramatic of a change requires re-tuning. Maybe tomorrow
« Last Edit: March 20, 2021, 08:44:29 AM by fh89 »

Offline acobaugh

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #72 on: March 20, 2021, 06:12:28 PM »
Saw the videos on youtube first thing this morning. You really have no sense of scale. It just looks like a table top coil with a small step ladder next to it. Good job on the splice. You gotta figure, worst thing that can happen is it burns up a second time!

Offline fh89

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #73 on: March 20, 2021, 08:33:09 PM »
Quote
You really have no sense of scale. It just looks like a table top coil with a small step ladder next to it.
It really does look like a smaller coil in some of these. The vertical breakout point one in particular looks almost tilt-shifted. It's funny because the primary is literally over shoulder height on me and I'm 5'10".

Quote
Good job on the splice. You gotta figure, worst thing that can happen is it burns up a second time!
Quote
On the other hand, if the splice works with the tight spacing then visually it looks great for a repair!
Thanks guys! I think I will have to eventually, there's already some carbon tracking from the flashover. Watching the video where it happened in slow-mo, I think an arc directly hit the secondary. Might have to go back to a longer breakout point to prevent this.

Offline davekni

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #74 on: March 21, 2021, 02:35:02 AM »
Was there any breeze?  I've noticed that wind can affect arc behavior - which way they tend to head.  (I don't run if there's much wind, as my secondary and top-load are only set in place, not fastened.)  I'm wondering if wind could have caused the arc back to a lower primary point, or at least made that more likely.

Nice performance!
David Knierim

Offline fh89

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #75 on: March 22, 2021, 06:42:22 AM »
Quote
Was there any breeze?  I've noticed that wind can affect arc behavior - which way they tend to head.  (I don't run if there's much wind, as my secondary and top-load are only set in place, not fastened.)  I'm wondering if wind could have caused the arc back to a lower primary point, or at least made that more likely.

It's funny that you mention that, because although it was calm at ground level, I think the coil being so tall when it is on the stand put it into light breeze because I did notice the blurry spark effect and the sparks were being pushed towards the secondary, especially at lower pulse widths.

I ended up killing the secondary again last night, this time I think it is from the direct secondary hits puncturing the insulation and shorting a turn. It failed in a different area than the splice and it is only two turns shorted. but I am going to rewind the secondary from scratch and try to optimize the design a bit more with a lower impedance and longer winding length. I think I am also going to double the MMC or build a completely new one with a higher Arms and 1+ uF capacitance.

Offline Hydron

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #76 on: March 22, 2021, 10:46:13 AM »
If V/turn is really an issue then you could try spacing the turns with nylon monofilament fishing line (may need to reduce wire diameter to keep turn number appropriate when spaced out a bit).
Might not help a lot though if the problem is direct hits from streamers (which won't care about your insulation or spacing!).

Offline davekni

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #77 on: March 22, 2021, 07:02:42 PM »
Taller secondary will also lower coupling, unless diameter is increased proportionately.  With windings spread out a bit, perhaps you could wind all the way to the bottom again to get coupling back up.

Have you considered a larger top-load?  That would help make the field more uniform down the secondary, which should reduce strikes to the secondary.  It should also help with longer arcs.  The larger top-load capacitance supports longer arcs before resonant frequency drops too far below primary frequency.  Even if building a new nice-looking toroid is too hard/expensive, it would be fun to experiment with a cheap hack top-load addition on top of your existing toroid.  Something like a sheet of 4x8' styrofoam insulation sheet rounded with a hot-knife and covered with aluminum foil.  Would look odd, but might get you another couple feet of arc length.  That might be something to try along with your planned lower-inductance secondary.
David Knierim

Offline Uspring

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #78 on: March 23, 2021, 05:56:26 PM »
Sad to hear that your secondary was damaged again. It is a really remarkable coil ranking near or at the top of in terms of power for QCW types. I hope you get it running again soon. Any chance you can take high fps movies of it? It would be very interesting to see how much gain in arc length you get from these long on times.

I think, that spacing the secondaries winding at the bottom will decrease coupling. Coupling depends much on the overlap of primary and secondary fields and winding spacing will decrease it. I haven't calculated the effect, though.

I found Mads remarks and links to the whiplash effect interesting. How much the voltage gradient along the secondary is affected depends much on the speed of voltage change of the top load during a ground strike. From Hydrons top load measurements a typical value would be maybe 100 kV/us. That voltage jump travels down the secondary at a speed of about 400 km/s, so the jump is about 40 cm long. That means a 100 kV jump along 40 cm length. Quite a lot but it doesn't last very long.

The jump travelling speed can be estimated, by calculating or measuring the secondary resonance frequency without a top load. The coil is then a quarter wave resonator, so that frequency and wavelength is known. From this the speed of the wave can be calculated.

Hydron has made some measurements of secondary bottom currents. Whiplashes could be nicely observed there. AFAIK, there weren't any ground strikes in his last data set.

Offline davekni

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #79 on: March 24, 2021, 02:49:42 AM »
To the extent that top-load and primary/strike-rail diameters are large compared to secondary length, there should be minimal whiplash.  Field up the primary will be roughly uniform, the field between two parallel plates of an air-dielectric capacitor.  Of course, in a real coil the diameters aren't semi-infinite.  Still, the whiplash voltage should be much less than would be experienced by a coil with no top-load.  I suspect that electric field non-uniformity up the secondary is driven more by magnetic coupling from the primary than from top-load voltage transients.
David Knierim

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Re: BrOdin coil; the swole DRSSTC Running at 15ms!
« Reply #79 on: March 24, 2021, 02:49:42 AM »

 


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post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
OmGigaTron
March 22, 2024, 11:30:09 PM
post Smoke Screen Machine Protect 950 XP - Teardown of a Smoke Cannon!
[Electronic Circuits]
Mads Barnkob
March 22, 2024, 10:20:35 PM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Benbmw
March 22, 2024, 09:21:13 PM
post Re: What actually kills MOSFETs?
[Beginners]
AstRii
March 22, 2024, 03:37:11 PM
post What actually kills MOSFETs?
[Beginners]
FPS
March 22, 2024, 05:09:20 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 22, 2024, 03:57:54 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 22, 2024, 02:59:25 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 21, 2024, 06:31:42 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
rikkitikkitavi
March 21, 2024, 03:08:01 PM
post Re: [WTS] IGBT, Ferrite, Capacitors, Tools, PSU, Industrial components and parts
[Sell / Buy / Trade]
Mads Barnkob
March 21, 2024, 01:37:32 PM
post Re: Difference between these transformers
[Transformer (Ferrite Core)]
Alberto
March 21, 2024, 11:42:07 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 21, 2024, 04:09:14 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 21, 2024, 02:15:31 AM
post My Homemade Structural Analysis X-Ray Machine
[X-ray]
Luca c.
March 21, 2024, 01:35:40 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 20, 2024, 10:40:00 PM
post Re: Difference between these transformers
[Transformer (Ferrite Core)]
Mads Barnkob
March 20, 2024, 08:03:41 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Mads Barnkob
March 20, 2024, 07:51:57 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 20, 2024, 10:39:47 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 20, 2024, 04:09:59 AM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 20, 2024, 01:13:23 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
March 20, 2024, 12:45:16 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 20, 2024, 12:30:30 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 11:12:24 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:47:49 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:44:19 PM
post Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 19, 2024, 06:52:09 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 19, 2024, 05:02:44 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Mads Barnkob
March 19, 2024, 05:01:41 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 04:31:02 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 03:59:54 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 06:41:39 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
davekni
March 19, 2024, 04:05:49 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
OmGigaTron
March 18, 2024, 09:08:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 09:07:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
Twospoons
March 18, 2024, 08:57:06 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
MRMILSTAR
March 18, 2024, 03:51:33 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:59:46 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:33:25 PM
post Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 11:02:12 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Twospoons
March 18, 2024, 02:36:11 AM
post Re: Best forum for vacuum tube amplifiers?
[General Chat]
Mads Barnkob
March 17, 2024, 07:42:55 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:15:14 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 05:05:04 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
davekni
March 17, 2024, 04:50:51 AM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Twospoons
March 17, 2024, 04:45:17 AM
post 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:17:51 AM
post Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Terry
March 17, 2024, 01:29:32 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 17, 2024, 12:33:06 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
March 16, 2024, 08:46:20 PM
post Re: Bleeder resistor for MMC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
March 16, 2024, 08:39:24 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
March 16, 2024, 08:21:44 PM
post Best forum for vacuum tube amplifiers?
[General Chat]
yourboi
March 16, 2024, 08:20:13 PM

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