Help Identifying AC Flyback - Page 1
Forum section: electronics / beginners

author: CompDude956
author_rank: Newbie
timestamp: July 31, 2017, 01:45:44 pm
content: So to start off... I've been playing around with high voltage things for a while and got into the flybacks and drivers side of things. I don't know too much about them -Yes! I am aware of the dangers- so I've come here to make my first post on identifying a flyback transformer I found in an old (1982) Sony Trinitron KV-1946R.I'm not sure what this thing In line with the high voltage output is.If it is some sort of rectifier or diode, does that mean that this transformer is AC? I haven't removed the transformer from the board, but the board is out of the television and I can take a better picture if needed. Any help and other advice on identifying flybacks and other parts in an old tube tv that may go well with some high voltage project would be greatly appreciated!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 31, 2017, 02:14:12 pm
content: Think it's something to do with generating two nearby anode voltages. I forget what the physics function is, but this talks about the component a bit anyway:https://www.repairfaq.org/REPAIR/F_monfaqd.html#MONFAQD_012Tim

author: Ian.M
author_rank: Super Contributor
timestamp: July 31, 2017, 02:54:33 pm
content: Quote from: CompDude956 on July 31, 2017, 01:45:44 pmNo. that's a diode split LOPT with a separate HSTAT divider unit.Seehttps://www.manualslib.com/manual/1002525/Sony-Kv-1946r.html?page=6#manualThe HSTAT unit (Horizontal static convergance) is unique to Sony Trinitron tubes - it provides an adjustable voltage to an electrostatic lens that 'bend' the beams from the PIL guns so they meet at the screen. Its ground leg current is often used for EHT sensing for overvoltage protection and sometimes for regulation.When driven properly the LOPT has a pulsed DC output rated for up to 25KV, and needs a capacitive load, As large 30KV caps are difficult to come by, you may need to build a Leyden jar. However driving a LOPT can be quite tricky for a novice as you cant simply copy the TV circuit because you don't want all the complexities of the pincusion correction and centering circuits nor do you want to have to keep the scan coil hooked up, so some experimentation with drive waveforms is required, gradually increasing the supply voltage till the correct nominal output voltage is measured on an EHT meter, while monitoring the peak voltage on the LOPT output transistor snubber network and the peak current to try to avoid blowing the transistor.If in doubt about CRT TV parts - Find the service manual and look at the schematic!

author: floobydust
author_rank: Super Contributor
timestamp: July 31, 2017, 05:54:04 pm
content: I know that thing inline is the focus voltage divider, note the potentiometer to adjust focus.

author: CompDude956
author_rank: Newbie
timestamp: August 01, 2017, 05:34:02 am
content: Thank you all so much I looked in the service manual for this tv on "manualslib.com" and couldn't read the part in there. So this flyback IS DCv then? Would I benefit from taking this HSTAT unit and putting it inline with some of my flyback projects? From the explaination Ian.M gave it's sounding like a very fine tuning for the pulsed output of the HV out. Also I have been thinking about making Leyden jars for very long spark gaps and voltage multipliers.

author: Ian.M
author_rank: Super Contributor
timestamp: August 01, 2017, 06:15:55 am
content: Quote from: CompDude956 on August 01, 2017, 05:34:02 amDid you find the schematics? In general to find the LOPT, look through them for a transformer with a lot of taps dricen by a power transistor labelled something like H-Out Line-Out Horiz-Out, or if there's a CRT marked on the schematics trace the final anode connection backwards.QuoteSorta. The output is pulsed and reverses slightly (and very weakly when negative going), but when connected to the capacitance of a CRT or Leyden jar will produce DC EHT with no extra high voltage components.QuoteNo benefit. It only works with a Sony Trinitron CRT where it drives an electrode that's purely an electrostatic load. Any attempt to use it for a load that draws significant current will burnout the HSTAT unit and its got relatively little adjustment range.QuoteYou want a thin walled straight sided wide mouthed clear glass jar so its easy to get good contact between the foil and the inside as any gap will reduce the capacitance.You could also use Nickel screening conductive spray paint or Aquadag for the interior electrode, but foil is cheaper and stands up better to high pulse discharge currents. Avoid 'wet' Leyden jars - the combo of salt water and EHT is *extremely* dangerous.You can make the bung out of white expanded polystyrene and the interior contact can be made of springy wire - bend a loop in the middle so there's no sharp points to leak by corona discharge, stuff the legs through a tight hole in the center of the bung then bend the legs out and curve the ends so they form a spring contact with the interior foil.Borosilicate glass (commonly used for laboratory glassware) has a dielectric strength of 30 KV/mm, so even a 2mm wall thickness will give you a >2x factor of safety. Soda Lime glass (common cheap glass) only has a dielectric strength of 13 KV/mm so you would need at least 3mm wall thickness and would have very little safety margin.The ONLY purpose of a Leyden jar is charge storage. The outer foil should always be grounded so their use in voltage multipliers is limited to the output reservoir cap.

author: CompDude956
author_rank: Newbie
timestamp: August 02, 2017, 06:02:56 am
content: I will definitely do more research on the Leyden jars and physics behind that. Your answers have blown me away and honestly confused a little bit but that's alright for me I'm only a 17yo hobbiest.I'd consider myself a pretty good solderer and tinkerer, but I don't have much knowledge other than a few small experiments all soldered up old school with no breadboard or anything to test on before finishing. I just recently got my first breadboard about 6 months ago and still haven't used it!Most of the parts I get are salvaged from mine and my buddies' trash electronics that end up in my basement and torn apart. So I usually go find a spec sheet of every chip and transistor to find out if it's worth using up my solder wick to remove. A while ago I did buy almost everything RadioShack had left during a closing sale of 90% OFF LOWEST CURRENT PRICE!! As you could imagine everything was only a few cents and I ended up spending a total of like $10 for it all.Anyways I think I've got enough information now on this flyback to play around with it and not be as clueless with it. Thank you!I will be posting another thread for a new project in the next few days most likely. Can't work on one thing at a time.