UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Closed Thread
 
Thread Tools
Old 1st Dec 2020, 12:12 am   #21
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,799
Default Re: How a Flyback works? induction and Ferris

Quote:
Originally Posted by FERNSEH View Post
At the end of the forward scan the magnetic field collapses so inducing the flyback pulse. Doesn't the formula -E = L . di/dt come into it?
DFWB.
Indeed it does... Twice!

Firstly when the inductor (primary) is jammed across the supply to get some current going Supply voltage = - L.(di/dt) And that sets the slope of the current ramping up for whatever amount of time it gets.

Then when the current is turned off you get E = -L(di/dt) where E is now th voltage transient and di/dt is the speed at which the switch can turn off the current.

So you get a voltage step-up factor equal to the ratio of the turn off to turn on current change rates. This is the basis of the boost converter SMPS, and with a secondary overwind, the voltage can be scaled up still further as in TV EHT, car ignitions, and high-frequency arc initiation in TIG welders.

Colour TVs go a step further and run the overwind into a voltage multiplying rectifier.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 1st Dec 2020, 12:02 pm   #22
Welsh Anorak
Dekatron
 
Welsh Anorak's Avatar
 
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,884
Default Re: How a Flyback works? induction and Ferris

On a practical level, I've used a non-metallic cable tie in the past and it has worked. Less successful has been when the ferrite core is cracked, chipped or broken.
__________________
Glyn
www.gdelectronics.wales
Welsh Anorak is offline  
Old 2nd Dec 2020, 6:04 pm   #23
Blazerfrazer
Triode
 
Join Date: Dec 2011
Location: Wimborne, Dorset, UK.
Posts: 21
Default Re: How a Flyback works? induction and Ferris

Hi All and thanks for all the contributions, im tempted with the cable tie but once fitted the LOPT has to be un-soldered each time a new one is needed. its not ideal because the engineer that’s fixing this chassis for me will have to do this when he repairs it and that means putting the metal top bracket on which might need to come off for access during repair. messy for him if he has to keep doing it, I don’t know if the bracket all needs to be tight and clamping the LOPT for testing. I would like to make a new clamp out of a material that won’t affect anything, im thinking about ordering a length of copper or brass. I realize that its not as strong as original but i have some deep 3mm nuts that should hold better on the threads. Can someone recommend a suitable material please? the old one was semi magnetic, be nice to know what that material was but i guessing one of the above should be safe?
Frazer
Blazerfrazer is offline  
Old 2nd Dec 2020, 8:45 pm   #24
Blazerfrazer
Triode
 
Join Date: Dec 2011
Location: Wimborne, Dorset, UK.
Posts: 21
Default Re: How a Flyback works? induction and Ferris

notice that i call it a LOPT now ��
Blazerfrazer is offline  
Old 2nd Dec 2020, 9:22 pm   #25
davyrocket2
Pentode
 
Join Date: Apr 2011
Location: Westgate On Sea, Kent, UK.
Posts: 246
Default Re: How a Flyback works? induction and Ferris

just a guess but maybe its alloy
davyrocket2 is offline  
Old 2nd Dec 2020, 9:50 pm   #26
Blazerfrazer
Triode
 
Join Date: Dec 2011
Location: Wimborne, Dorset, UK.
Posts: 21
Default Re: How a Flyback works? induction and Ferris

the original part thats broken stuck to the magnet but not as much as the mild steel one i made. perhaps original is stainless?
Blazerfrazer is offline  
Old 2nd Dec 2020, 10:02 pm   #27
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,799
Default Re: How a Flyback works? induction and Ferris

There are two classes of stainless steels: Austenitic and Martensitic. One is magnetic, the other isn't and I can never remember which way round they are.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 2nd Dec 2020, 10:29 pm   #28
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: How a Flyback works? induction and Ferris

Googled austenitic and this came up:

Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron, with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1000 K (727 °C); other alloys of steel have different eutectoid temperatures.


DFWB.
FERNSEH is offline  
Old 2nd Dec 2020, 11:24 pm   #29
Boulevardier
Octode
 
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 1,641
Default Re: How a Flyback works? induction and Ferris

Quote:
Originally Posted by Blazerfrazer View Post
notice that i call it a LOPT now ��


Mike
Boulevardier is online now  
Old 3rd Dec 2020, 12:02 pm   #30
Blazerfrazer
Triode
 
Join Date: Dec 2011
Location: Wimborne, Dorset, UK.
Posts: 21
Default Re: How a Flyback works? induction and Ferris

Hi, i just want to order something lol.

I found some Stainless Steel T303 rod on ebay that says its non-magnetic, its cheap.
The original is slightly magnetic... i wondering should i be looking for the magnetic variety? I found many types that are magnetic all with different chemical composition.
Do you think this rod is supposed to be slightly magnetic for its function in the LOPT? if not ill order the T303 stuff.

Ps for those that are interested, i will finish this thread with the final working monitor and a thanks to everyone.
Blazerfrazer is offline  
Old 3rd Dec 2020, 8:31 pm   #31
Blazerfrazer
Triode
 
Join Date: Dec 2011
Location: Wimborne, Dorset, UK.
Posts: 21
Default Re: How a Flyback works? induction and Ferris

That was supposed to say:

Ps for those that are interested, i will finish this thread with a picture of the final working monitor + a thanks to everyone for helping.

ive ordered the Stainless Steel T303
Blazerfrazer is offline  
Old 11th Dec 2020, 6:30 pm   #32
Blazerfrazer
Triode
 
Join Date: Dec 2011
Location: Wimborne, Dorset, UK.
Posts: 21
Default Re: How a Flyback works? induction and Ferris

Hi All, thought i would update.
I got my 304 stainless through and because i didn't want to mess it up, i made a former to help. Here is the new clamp in place, note the insulating plastic feet on the bottom of the ferrite. I was careful to make sure they went back in.

Click image for larger version

Name:	Fly-back (1).jpg
Views:	71
Size:	105.1 KB
ID:	222329

Click image for larger version

Name:	Fly-back (2).jpg
Views:	67
Size:	120.5 KB
ID:	222330

Click image for larger version

Name:	Fly-back (3).jpg
Views:	67
Size:	126.4 KB
ID:	222331

Click image for larger version

Name:	Fly-back (4).jpg
Views:	69
Size:	113.5 KB
ID:	222332

Click image for larger version

Name:	Fly-back (5).jpg
Views:	58
Size:	101.3 KB
ID:	222333
Blazerfrazer is offline  
Old 11th Dec 2020, 6:31 pm   #33
Blazerfrazer
Triode
 
Join Date: Dec 2011
Location: Wimborne, Dorset, UK.
Posts: 21
Default Re: How a Flyback works? induction and Ferris

Click image for larger version

Name:	Fly-back (6).jpg
Views:	75
Size:	87.0 KB
ID:	222334

Click image for larger version

Name:	Fly-back (7).jpg
Views:	67
Size:	81.5 KB
ID:	222335

Click image for larger version

Name:	Fly-back (8).jpg
Views:	64
Size:	109.5 KB
ID:	222336

Click image for larger version

Name:	Fly-back (9).jpg
Views:	73
Size:	100.5 KB
ID:	222337

Click image for larger version

Name:	Fly-back (10).jpg
Views:	58
Size:	120.1 KB
ID:	222338
Blazerfrazer is offline  
Old 11th Dec 2020, 6:33 pm   #34
Blazerfrazer
Triode
 
Join Date: Dec 2011
Location: Wimborne, Dorset, UK.
Posts: 21
Default Re: How a Flyback works? induction and Ferris

Its packaged up and off the the chap for repair now.
Frazer
Blazerfrazer is offline  
Old 11th Dec 2020, 7:03 pm   #35
stacman
Hexode
 
Join Date: Nov 2010
Location: Sheffield, South Yorkshire, UK.
Posts: 278
Default Re: How a Flyback works? induction and Ferris

Nice bit of engineering there, good to see a workbench too
Regards,Alan
stacman is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:41 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.