833C vttc. / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

833C vttc.

previous 1 2 3 4 next

Move Thread

LAN_403

Steve Ward

Mon Jul 28 2008, 01:04AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Lets not forget what shunts do. They effectively lower the mutual inductance between the primary and secondary, which is equivalent to lowering the coupling, which is the same as having excessive leakage inductance, i.e. a ballast. This extra inductance will have a voltage drop that is proportional to the current through it. So, get those shunts outta there!

Also, id suggest using a variac, at least the first time, to power up the filaments with your home-brew transformers, just to make sure you didnt over do it. Remember to probe the filament voltage AT the pins of the tube, otherwise you arent accounting for voltage drop in your wiring and connections.

For a soft start, i often used a series resistance of a few ohms (1-5 would be about right) rated for 25-50W. Just run the resistor in series with the filament supply, and short it out with a switch after a couple seconds. With the resistor you should get up to a nice glow (like a low wattage light bulb), and then you can hit it all the way with full power.

quicksilver

Mon Jul 28 2008, 02:04PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

MOTS being as the least expensive part of most any setup, work to get that end correct! I'd knock the shunts out, sure. But I'd also get others to insure that what I was pairing up with that big old tube was what was really appropriate!

....Meaning that if it's not really on the money, set up another one that puts out the exact voltage/current level you need. Working with a small x-former and trying to form the secondary correctly might be a pain.......MOTS are cheap.

Arcstarter

Mon Aug 04 2008, 12:34AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well i made some progress on the base and did a little bit of wiring.

I bought two switches, one for the filament supply and one for the B+ supply. I also did the wiring from the filament mot and mounted the socket, switches, and mot's. The voltage at the pins of the tube is 10.1 volts. YAY! I suppose tomorrow i will rig up a soft start switch and resistor. I also ordered the wire for the wiring and primary yesterday so it should be here tomorrow or the next day unless he doesn't ship until payment is received. I also found a riding mower today that seems to be in good condition so i should be able to make a little more money, which will go towards this projects and then my 6 inch coil.

Just the base's current progress.

The bottom of the base. Filament supply mot on left and B+ supply on the right. I have the filament bypass capacitor mounted below it for easy of wiring. I just put some terminals on the capacitor and screwed the socket down.

I had to mount the socket on top of two blocks of wood because of the screws that protruded from the socket and i could not just screw them into the wood or it would scrape the ground. I know that this thing is going to be much bigger than necessary, but i am no good at this kind of thing. I should have just mounted the socket on the top so the top of the base could be much lower, but i want the tube to be as far away as possible from the sparks. I still need to make a topload, but after mowing all the grass with my new mower, i should be able to make a nice on :P.

Here is the picture of all of the components:

The big round red thing is a 45kv 2nf doorknob capacitor from chris hooper(Dr. Spark), the white thing that is half red it the resistor and choke for the tank circuit. the brown green and blue things are the grid leak cap and resistor. The rest is pretty obvious.

Arcstarter

Mon Aug 11 2008, 09:10PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

My 120 feet of 12 gauge wire just got here so after i get the 6 inch pvc pipe i will wind the primary and the feedback and then i can put it all together for its first light. I haven't done anything with the base or mounting anything yet. I am going to put the soft start on some day.... I already (kinda getto) put the 20 watt one ohm resistor on a heatsink... since it will only have to be on for about 10 seconds i expect it to be alright, i do not care if i smoke it at all... as long as the filament on the tube is good for a long while.

I also got that riding mower running good, but i need a new drive belt cause my friend wrecked on it... so i should have many projects going soon. I also bought some ucc37322-321 for a sstc.

Dr. SSTC

Tue Aug 12 2008, 09:50AM

Registered Member #1407 Joined: Fri Mar 21 2008, 07:09AM
Location:
Posts: 222

Arcstarter wrote ...

I also got that riding mower running good, but i need a new drive belt cause my friend wrecked on it... so i should have many projects going soon. I also bought some ucc37322-321 for a sstc.

is that sstc maybe going to be uzzors pll or steve wards mini

Marko

Tue Aug 12 2008, 10:11AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Woah, where do you guys get those 2nF 45kV doorknob capacitors? What's their kVar rating, Chris?

Arcstarter, isn't that case kind of too big? (MOT's look dwarfed in it), otherwise looking forward your project.

I would be careful though with use of PVC for secondary forms - unless you will only run the coil pulsed at low duty cycles it might overheat and buckle on long runs. Of cheap materials cardboard is best for secondaries that are going to get hot.

Marko

Arcstarter

Tue Aug 12 2008, 05:40PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Dr. noob wrote ...

Woah, where do you guys get those 2nF 45kV doorknob capacitors? What's their kVar rating, Chris?

Arcstarter, isn't that case kind of too big? (MOT's look dwarfed in it), otherwise looking forward your project.

I would be careful though with use of PVC for secondary forms - unless you will only run the coil pulsed at low duty cycles it might overheat and buckle on long runs. Of cheap materials cardboard is best for secondaries that are going to get hot.

Marko

Yes, i was afraid of the heating problems... I am not too worried about that either cause this will only run for awhile, nothing more than a few minutes(like 1-2 minutes). Yes, this case is ABSOLUTELY TOO BIG... I am kinda PO'ed about it. I made it so big so that i could fit the tube on the bottom so that it would be further away from the sparks. Steve Ward was talking about how there was high voltage building on his MO caps, so i figured it is best to keep the tube far away.

EEYORE

Tue Aug 12 2008, 08:51PM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

Arcstarter wrote ...

Yes, quite a big case indeed! More like a doghouse!

You could fit a piggy in there instead of the MOTs.
Better put it on wheels...
You could use acrylic for the secondary...I think it works out well for these things...Ebay usually has it on there. (Much more $$$ than PVC though).
Matt

Dr. Drone

Wed Aug 13 2008, 03:38AM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

Arcstarter

Wed Aug 13 2008, 03:51AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well, i decided i would go ahead and finish up and i will make a new base another day. Basically i just want to try it out on my current base and i will just make a new base later.
make a new base later
make a new base later

Anyway.....

First light was today. My doubler wouldn't work quite yet so i tried with ac in and straight from the mot:4 inch spark... Also no tuning. This is what i expected but is this good?

excuse the cursing :P.

previous 1 2 3 4 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob