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Finished up ZVS need advice.

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Dr. Dark Current

Sun Jun 21 2009, 08:01AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

brtaman wrote ...

Are you sure about the 34mA though? That would make that power 420W!? 3.4mA?

I'm not sure but should be in the ballpark. Remember, its 420VA, not W on the output! It can be flowing 30mA through the secondary but the arc drop could be just for example 2kV, which is 60W.

EDIT: In my original post I said 350VA and calculated the current for 12kV. For 14kV that would be less.

Harry, I believe his transformer is the diode split type so he can just put a capacitor across the output.

brtaman

Sun Jun 21 2009, 11:37AM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Hey,

Thanks for all the help everyone! I am like a sponge at the moment soaking up every bit of info possible. :)

Dr. Kilovolt, you are correct it is just a simple new-age rectified flyback. The funny story is; I saw an ancient looking TV, that I was sure must be black and white (really ancient looking), at a friends house, of course I asked him politely if he needs it :). Needless to say he was happy for me to take it off his hands. When I came home my jaw dropped when I pulled out the circuit...it had a rectified flyback!? Is it a rule that black and white tv's must have AC flybacks, or did the later BW models possibly have rectified diodes?

this must be one of the oldest color TVs i have come across...can post a pic, if you guys are interested.

I am probably going with an RSG on the v.2 TC. Teslamap suggest that a higher ideal capacitance is required? This seems illogical as with an RSG I have full control of BPS, or is it just a basic guide line? How accurate is TeslaMap in your opinion?

Thanks
brtaman

EDIT: I forgot to ask. Ever since I tuned the driver to pull 8+amps at 12 (8.6 peak atm) by increasing capacitance it seems that the arc is less powerful? How is this possible, there is an extra 24W going into the circuit. It doesn't burn as hot (more blue as opposed to white, less current) and striking distance for the arc grew only a tiny bit? Am I wasting energy and should just go back to 4+4 turns and the 6.2amp or is the new power there just not noticeable to my eye?

The driver is not getting hot (quite warm after 5-10 minutes of arcing)?

Proud Mary

Sun Jun 21 2009, 11:56AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Colour, as such, doesn't have anything to do with it, son.

TV EHT supplies have undergone four basic evolutions, roughly, with small variations and overlap in time, as follows:

1. Pre-WW2 - simple EHT transformers i.e. 50/60Hz mains in, 50/60Hz EHT out.

2. Post WW2: Flyback transformers using an external diode half wave rectifier thermionic valve (tube) and a winding to supply the filament of the valve. No voltage multiplication, so these flybacks have a fairly high output voltage. *

3. Silicon diodes enter the historical picture: Flyback transformers having an external voltage multiplier circuit, which is usually a doubler or tripler encapsulated in a plastic block. The focus voltage supply is often, but not always, taken from a tap some way up the multiplier.

4. Split secondary flybacks, where two or three secondaries are each separated by a diode buried in the winding, the voltage of each stage added together in series, and output via a single thick lead which supplies the main CRT supplier. This is what we calls a "DC flyback"

Split secondaries (i.e. DC flybacks) became general after about 1980.

* I just bought three of these, unused, and still in their original boxes, with guarantees still inside, and all for Â£5 /NOK 52 /Euro 6/ US$ 8.20.
Do I just stash them under the bed and get them out to gloat over now and again, or should I make something with one of them?

brtaman

Sun Jun 21 2009, 12:02PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Ohhh, I was under the impression that the rule of thumb was BW-AC Color-DC, thanks for clearing that up. Decent BW TV's with AC flybacks are getting harder and harder to find at least from my perspective (4 TV's in past month...all DC -.-), got a lot of cool caps, diodes and transistors though. :)

Proud Mary

Sun Jun 21 2009, 12:13PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

brtaman wrote ...

Ohhh, I was under the impression that the rule of thumb was BW-AC Color-DC, thanks for clearing that up. Decent BW TV's with AC flybacks are getting harder and harder to find at least from my perspective (4 TV's in past month...all DC -.-), got a lot of cool caps, diodes and transistors though. :)

It does often break down like that in practice, but if you think of early US colour televisions from the late 1940s to early 1960s, before silicon diodes came into general use, then you'll see that an old colour TV could still have an AC flyback with a thermionic valve half-wave rectifier.

Most of the type with external rectifiers will long ago have gone to pollute the sub-surface water in landfill sites, so it's a sheer matter of luck if you can find any of the older type.

Early colour televisions cost three or four times as much as black-and-white, and there was a lot of prestige to owning one, which is why you find a long period - almost 20 years - where more B&W televisions were produced than colour. In Britain, colour television was not introduced until 1967.

brtaman

Sun Jun 21 2009, 12:37PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

"* I just bought three of these, unused, and still in their original boxes, with guarantees still inside, and all for Â£5 /NOK 52 /Euro 6/ US$ 8.20.
Do I just stash them under the bed and get them out to gloat over now and again, or should I make something with one of them?"

Get them out take a couple of pics and gloat. :D Its what I would be doing. ;)

"EDIT: I forgot to ask. Ever since I tuned the driver to pull 8+amps at 12 (8.6 peak atm) by increasing capacitance it seems that the arc is less powerful? How is this possible, there is an extra 24W going into the circuit. It doesn't burn as hot (more blue as opposed to white, less current) and striking distance for the arc grew only a tiny bit? Am I wasting energy and should just go back to 4+4 turns and the 6.2amp or is the new power there just not noticeable to my eye?

The driver is not getting hot (quite warm after 5-10 minutes of arcing)?"

What is your opinion on this? I Edited the wrong post -.-

Again thanks for all the time you are taking to answer my novice questions.

brtaman

Proud Mary

Sun Jun 21 2009, 12:55PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Maybe the core is saturating. If you think about a flyback in normal television service you're looking at a device optimized for an output of 50W or so.

Dr. Dark Current

Sun Jun 21 2009, 01:05PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Harry wrote ...

Maybe the core is saturating. If you think about a flyback in normal television service you're looking at a device optimized for an output of 50W or so.

50W for flyback converter so the core is huge, good for MUCH more with forward converter.

brtaman

Sun Jun 21 2009, 01:28PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

I was also thinking some saturation is occurring at 3+3 winds? Maybe its just my eyes deceiving me but I would venture to say there is less power now than with 4+4, what I don't understand is where all the other energy is going...if the driver was heating up rapidly I would accept heat loss, but it is staying just as cool as before.

Proud Mary

Sun Jun 21 2009, 01:46PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Maybe you need to change the value of the toroidal choke?

There's a lot better folk to advise you on this particular circuit in here than me, though - I built one a few years ago, when I first joined 4HV, and it worked right away just like it said on the can.

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