Mains Staccato / T-200 VTTC

[304er]

Hi all,

First off I want to reference this just posted thread:

Mains Staccato / SGTC

So after the success of this...

I again got to wondering on one of my VTTC's. Specifically my "new" old T-200 one. This coil also has origins in the 1980's also. This coil is normally run on just normal AC with a fairly heavy plate transformer(38 lbs). I have run this coil with my now modified German Staccato controller and a SSR switching the cathode like normal. Works great and everything nice and smooth running. Single shots and burst modes all work great. Now this coil does not get very good swords. The frequency is about 100kHz too high. This coil never originally back then had this in mind at all. But it does have interesting bushy sparks though.

So I have decided to try hooking up the SSR to the 120vac mains input on the plate transformer. Going to switch the primary of the transformer direct again. And pretty much as expected, this works great. SSR zero crossover working very well. Any controller changes are very smooth and very responsive. This coil puts out about a maximum 20" sparks at times.

I have a link to a few pictures of this setup and a video I took of this running this way:

https://photos.app.goo.gl/fMz5gAGDmjMpvq5P9

I want to say this my even seem to run even smoother than before.
Also the plate transformer runs now even cooler than before, since again not constantly energized. I have also run this coil many times now no problem this way. Some runs over 2 hours even.

I currently do not remember the idle current of this transformer, but it not much when I last checked. Now this transformer when the tube cathode was switched, it would get a little warm. Now running this way barely warm at all. Actually maybe a little surprised some here.

And a final note here, this way will not work for a level shifted supply.
I thought about this because of the charge capacitor will not charge up properly. Decided to do a slightly risky test just to be sure. I took the removed bigger old MOT with a level shifter that is now removed and not going to be used anymore on the 304 coil and test on this T-200.
As I thought this does not work well at all! Got some strange occasional small poor sparks. Did not run long for fear of hurting something.
Next I hooked this up for regular cathode switching and the coil would  now get 27" sparks maximum. But this is pushing this old coil very hard. Primary wire especially. It is not very big wire at all!!! Gets quite hot now.
Tube does fairly ok. And well since no fan on the MOT it heats up quite quickly like they normally do. Just wanted to do a quick test this way also, just to verify.

I put the plate transformer back on switching the primary again and let it run for over an hour. Still all working great.


Chris Reeland
Ladd Illinois USA

[Duane B]

Hi Chris, nice looking coil! I am impressed with the output and the staccato controller seems to work great. I see some light flashes coming from the corner of the plate transformer. Are these flashes electrical, or just reflections from the sparks coming from the top of the secondary? Again, good work!

[304er]

Hi Duane,

Thanks again.
Yeah this old fella does pretty good. It actually has a very inefficient primary, but does pretty good as is seen. That said, tuning...tuining....said twice on purpose is key despite other problem areas of this coil design. Getting the grid leak set up was very challenging on this fella while also getting the tank capacitance right at the same time. Dozens and dozens of trys changing things.

That said, why one would not design new better primary and this includes feedback...well for nostalgia sakes for me here :^) And actually...I enjoy a good challenge...

I like the some old with new here.

Oh...the flashing on the transformer is on some threads sticking out from the core clamp bolts. I have wrapped one wire lead to this which the whole core is grounded and bent the other wire lead straight up the side of the little neon bulb as a little antenna for my fun little RF detector.
I do something similar on my 304 VTTC also, which is a "green" neon bulb.

Mentioning my 304, this coil now has always been about getting better, good efficient design.
That said tuning is still very challenging to getting right.
Not sure if you have seen the other videos of it yet, but it "uses" at times most of the yard stick hanging behind it. Pretty good for just a single MOT and a single tube and no over voltage input. Using 120v in to MOT.

Oh... the very temporary 27" was achievable because of the vacuum variable capacitor this has in parallel with the 2 mica tank caps.
I had extra wiggle adjustment left to put on more proper capacitance needed using this VVC.

Chris Reeland
Ladd Illinois USA