Author Topic: New LOPT / Flyback transformers available?  (Read 7399 times)

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Offline @rt

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New LOPT / Flyback transformers available?
« on: February 20, 2016, 02:52:58 pm »
Hi Guys :)
I’m just wondering if a modern substitute is available for the flyback transformers from CRT TVs
for use with ZVS drivers in high voltage projects?
I am aware you can still eBay the NOS TV stuff, but still wondering if there’s any substitute for this?
Cheers, Art.

 

Offline CM800

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Re: New LOPT / Flyback transformers available?
« Reply #1 on: February 20, 2016, 03:24:24 pm »
Hi Guys :)
I’m just wondering if a modern substitute is available for the flyback transformers from CRT TVs
for use with ZVS drivers in high voltage projects?
I am aware you can still eBay the NOS TV stuff, but still wondering if there’s any substitute for this?
Cheers, Art.

There are quite a lot of ones you can buy on places like alibaba and aliexpress
Equally you could wind your own for more power on some cores off ebay, or you could get a few custom made in china and sell the rest off.

Try find an old high frequency x-ray transformer too, they are great fun.
 

Online mikeselectricstuff

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Re: New LOPT / Flyback transformers available?
« Reply #2 on: February 20, 2016, 03:40:14 pm »
or high frequency neon sign transformer
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Online NiHaoMike

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Re: New LOPT / Flyback transformers available?
« Reply #3 on: February 20, 2016, 03:41:10 pm »
What about automotive ignition transformers?
Cryptocurrency has taught me to love math and at the same time be baffled by it.

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Online mikeselectricstuff

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Re: New LOPT / Flyback transformers available?
« Reply #4 on: February 20, 2016, 06:38:40 pm »
What about automotive ignition transformers?
different type of beast - typically laminated iron core instead of ferrite.
 
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Offline @rt

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Re: New LOPT / Flyback transformers available?
« Reply #5 on: February 23, 2016, 05:20:22 am »
Thanks for replies :)

It is actually for Tesla coil. Spark gap for starters, but I’d like to refine it further than that afterwards.

I have ZVS driver here, and a LOPT on the way. From there I figure it should be possible to charge a HV capacitor that discharges through
a spark gap to complete a coil since I can’t control the frequency of the ZVS driver with frequency feedback from the Tesla Coil (that I know of).

I have a neon former, but I’d like to keep the project able to be powered with SLA batteries.
 

Offline @rt

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Re: New LOPT / Flyback transformers available?
« Reply #6 on: February 26, 2016, 04:33:29 am »
Hi Guys :)
Another question...
I have the LOPT here now, and with a single 12V SLA I can get just shy of a 10cm continuous arc between it’s
anode and “screen” wire. Much lesser an arc from it’s “focus” wire which is actually the stronger HT cable.

When using the “screen” wire a couple of pins under the LOPT were also arcing, so I bridged them for a better
result straight from the wire. Is this the best place to use on the other side of the HT anode?

Also, are the “screen” and “focus” adjustment screws some sort of pot, or variable capacitors to tune the
resonant frequency of their associated windings? I assume the latter because they change the nature of the arc
from a sharp streamer, to something more glowing and not as tight.
Cheers, Art.
 

Online mikeselectricstuff

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Re: New LOPT / Flyback transformers available?
« Reply #7 on: February 26, 2016, 01:14:06 pm »

Also, are the “screen” and “focus” adjustment screws some sort of pot, or variable capacitors to tune the
resonant frequency of their associated windings? I assume the latter because they change the nature of the arc
from a sharp streamer, to something more glowing and not as tight.
Cheers, Art.
No, they are pots providing an adjustable voltage divided from a lower voltage tap. If you've shorted an  output of these then you will have been adjusting the loading on the transformer
Lots of into on TV LOPTs here
http://www.repairfaq.org/sam/flytest.htm
Including this typical schematic ( complete with ASCII art-Emotion clash!)

                                        +--|>|-----------o  HV to CRT
              _        1             ::(   CR1             (25 to 30 kV,
             |   B+  o-------------+ ::(                    suction cup on
    Drive    |                      )::(                    fat red wire)
    winding <                       ):: +-------+
             |             1.32     )::         |
             |         2            ):: +--|>|--+
             |_  HOT o-------------+ ::(   CR2
              _        3             ::(
             |   50  o-------------+ ::(
             |                      ):: +-------+
             |         4    .11     )::         |
             |   35  o-------------+ :: +--|>|--+
  Various    |                      )::(   CR3  |
  auxiliary <               .28     )::(        /
  windings   |         5            )::(        \<-------o  Focus
             |   16  o-------------+ ::(        /          (3 to 10 kV,
             |                      )::(        \           orange wire)
             |         6    .12     )::(        |
             |_   0  o----------+--+ ::(        |
              _        7        |    :: +--+    /
             |   H1  o----------|--+ ::    |    \<-------o  Screen
 CRT Heater <          8    .08 |   )::    |    /          (200 to 800 V,
             |_  H2  o----------+--+       |    \           brown wire)
                                |          |    |      9
                                |          +----|--------o  To CRT DAG
                                |               |            ground
                                +---------------+

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Offline @rt

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Re: New LOPT / Flyback transformers available?
« Reply #8 on: February 26, 2016, 02:13:59 pm »
Ok thanks, that’s interesting. It looks like the secondary turns ratio would be better if I used the Gnd pin rather than screen.
I wonder now what pins I’ve connected together.

This is powered by two small SLA in series, but I might have wrecked one by discharging it too much today.

 

Offline mmagin

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Re: New LOPT / Flyback transformers available?
« Reply #9 on: February 26, 2016, 09:16:20 pm »
I was seeing this topic pop up so frequently that I got to thinking:

Could one construct a core for such a transformer by making nice miter cuts on appropriate ferrite rods and then epoxying them together?
It seems like then, so long as you wound the high voltage side on an insulating bobbin and potted it appropriately (this probably involves a vacuum pump and stuff), you could build such a thing from scratch in single quantities.

Or maybe, there are existing cores that are big enough, that would be easier.  Hmm, maybe (U-cores and matching I-core pieces): http://www.digikey.com/product-search/en?FV=ffecb73b&stock=1
Not so cheap, but smaller cores would probably make it harder to get the isolation you'd want.
 

Offline @rt

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Re: New LOPT / Flyback transformers available?
« Reply #10 on: February 27, 2016, 01:39:10 am »
Yes you could do it with ferrite from old AM radios if the material is the same.
The one I have is done that way. Not a solid piece at all.
 

Offline @rt

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Re: New LOPT / Flyback transformers available?
« Reply #11 on: March 03, 2016, 04:11:18 pm »
Hi Guys :)
Another question if I may...
Does the spark gap not necessarily fire at the coil resonant frequency,
and just ringing of the primary excite the secondary?

 

Offline @rt

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Re: New LOPT / Flyback transformers available?
« Reply #12 on: March 09, 2016, 02:07:57 pm »
Ok, I got my first streamers breaking out directly from the torus today,
just from changing my homemade foil capacitor to this array,
which is an arbitrary capacitance value so far, but I figure it’s 35kV, 2000pF.

For all I know I still need to add or subtract capacitance, but will have to figure out by trial and error.
My primary is just insulated wire with some taps that isn’t easily fine tuned like the copper tube will be, so that’s a consideration.



 

Offline station240

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Re: New LOPT / Flyback transformers available?
« Reply #13 on: March 10, 2016, 07:53:09 pm »
Came across this on Banggood when looking for something else, thought of this thread.
http://www.banggood.com/DC-6V-12V-To-500Kv-High-Voltage-Generator-Inverter-Boost-Power-Module-p-1004753.html

Those paying attention will note that 500Kv @ 0.5A = 0.25MW clearly impossible :palm:
Reading the reviews, 36kV is more realistic.
 

Offline mmagin

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Re: New LOPT / Flyback transformers available?
« Reply #14 on: March 10, 2016, 08:03:06 pm »
Came across this on Banggood when looking for something else, thought of this thread.
http://www.banggood.com/DC-6V-12V-To-500Kv-High-Voltage-Generator-Inverter-Boost-Power-Module-p-1004753.html

Those paying attention will note that 500Kv @ 0.5A = 0.25MW clearly impossible :palm:
Reading the reviews, 36kV is more realistic.

I was going get at the obvious, "can't be 500 KV and that small", but then I noticed this image and was like, "if they can't even get the dimension right, you know it's quality." :)
 

Offline @rt

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Re: New LOPT / Flyback transformers available?
« Reply #15 on: March 11, 2016, 12:56:11 pm »
Ah yeah, I went for what I thought looked largest, and probably most expensive of the new boxed ones on eBay.
Next thing is I’m having two acrylic discs made to mount together with nylon standoffs,
and a third (bottom) tier for the batteries and electronics.

I forgot to say in the video, I strongly suspect these caps are secondhand but sold as new.
The leads have different lengths, and some legs are still tinned with solder :D
Who in the USA would desolder all of these and sell cheap in packs of 25?
Still, it appears to go ok.

« Last Edit: March 11, 2016, 12:59:17 pm by @rt »
 


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