New LOPT / Flyback transformers available? - Page 1
Forum section: electronics / projects

author: @rt
author_rank: Super Contributor
timestamp: February 20, 2016, 02:52:58 pm
content: Hi GuysI’m just wondering if a modern substitute is available for the flyback transformers from CRT TVsfor 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.

author: CM800
author_rank: Frequent Contributor
timestamp: February 20, 2016, 03:24:24 pm
content: Quote from: @rt on February 20, 2016, 02:52:58 pmThere are quite a lot of ones you can buy on places like alibaba and aliexpressEqually 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.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 20, 2016, 03:40:14 pm
content: or high frequency neon sign transformer

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 20, 2016, 03:41:10 pm
content: What about automotive ignition transformers?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 20, 2016, 06:38:40 pm
content: Quote from: NiHaoMike on February 20, 2016, 03:41:10 pmdifferent type of beast - typically laminated iron core instead of ferrite.

author: @rt
author_rank: Super Contributor
timestamp: February 23, 2016, 05:20:22 am
content: Thanks for repliesIt 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 througha 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.

author: @rt
author_rank: Super Contributor
timestamp: February 26, 2016, 04:33:29 am
content: Hi GuysAnother 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’sanode 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 betterresult 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 theresonant frequency of their associated windings? I assume the latter because they change the nature of the arcfrom a sharp streamer, to something more glowing and not as tight.Cheers, Art.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 26, 2016, 01:14:06 pm
content: Quote from: @rt on February 26, 2016, 04:33:29 amNo, 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 transformerLots of into on TV LOPTs herehttp://www.repairfaq.org/sam/flytest.htmIncluding this typical schematic ( complete with ASCII art-Emotion clash!)+--|>|-----------o HV to CRT_ 1 :CR1 (25 to 30 kV,| B+ o-------------+ :suction cup onDrive | ):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 ScreenCRT Heater < 8 .08 | ):: | / (200 to 800 V,|_ H2 o----------+--+ | \ brown wire)| | | 9| +----|--------o To CRT DAG| | ground+---------------+

author: @rt
author_rank: Super Contributor
timestamp: February 26, 2016, 02:13:59 pm
content: 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.

author: mmagin
author_rank: Frequent Contributor
timestamp: February 26, 2016, 09:16:20 pm
content: 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=1Not so cheap, but smaller cores would probably make it harder to get the isolation you'd want.

author: @rt
author_rank: Super Contributor
timestamp: February 27, 2016, 01:39:10 am
content: 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.

author: @rt
author_rank: Super Contributor
timestamp: March 03, 2016, 04:11:18 pm
content: Hi GuysAnother 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?

author: @rt
author_rank: Super Contributor
timestamp: March 09, 2016, 02:07:57 pm
content: 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.

author: station240
author_rank: Unknown
timestamp: March 10, 2016, 07:53:09 pm
content: 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.htmlThose paying attention will note that 500Kv @ 0.5A = 0.25MW clearly impossibleReading the reviews, 36kV is more realistic.

author: mmagin
author_rank: Frequent Contributor
timestamp: March 10, 2016, 08:03:06 pm
content: Quote from: station240 on March 10, 2016, 07:53:09 pmI 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."

author: @rt
author_rank: Super Contributor
timestamp: March 11, 2016, 12:56:11 pm
content: 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 solderWho in the USA would desolder all of these and sell cheap in packs of 25?Still, it appears to go ok.