1. Home
  2. Electronics Repair
  3. Yoke Replacement

Yoke Replacement

This must be one of those "really desperate to fix it" projects. A little

9" color TV/radio combo I picked up in the trash, had a badly burned yoke. I was able to isolate and insulate the shorted windings, but disturbing the windings threw the convergence way off and the yoke was still as useless as ever. Now I just happened to have a good yoke from an identical CRT (27GDC85X), however it was designed for a completely different set. I installed it anyway, the vertical windings are a perfect match but the horizontal ones have too low an impedence - causes high-voltage shutdown unless powered with a Variac. I determined that the original yoke H winding was about 13.2 ohms, and the replacement yoke H winding is about 3.9. A bold idea came to mind; wind an impedence-matching transformer from an old flyback core and some magnet wire. I have several pounds of AWG 27 and 38 magnet wire that I could do this with. The question is: do I need a 1:1 turns ratio? I suspect I do, this means that the two windings would have the same number of turns but use different wire gauges. Think this would work? I know it's a lot more trouble than the old set is worth, but I'm not exactly busy these days and I hate to junk such a nice set. 9"-ers are not abundant in my supply, so it's certainly worth an hour or twos work to get this going. Thanks for any advice.
Reply to
Chris F.
Loading thread data ...

little

I

as

winding

bold

the

is

More the the impedance is the inductance. Try winding an inductor and placing it in series with the yoke, that may well work.

Reply to
James Sweet

I was just thinking the same thing, I will give that a try and see what happens.

yoke.

the

38

nice

hour

Reply to
Chris F.

In article , Chris F. wrote: ...[snipped]...

The turns ratio would need to be the square root of the impedance ratio. But bear in mind that the DC resistance isn't the same as the impedance at the operating frequency. I'd guess 2:1 turns ratio would be close (the 2 on the driving side and the 1 on the yoke side.) Wire gauge is not critical, use the thickest that fits mechanically. However this may not work well, due to losses and disturbing the expectations of the driving circuitry.

However, I suspect there is a _much_ easier solution. Yokes usually have two separate coils, connected in either series or parallel. There's a good chance you'll find yours is in parallel, in which case if you convert it to series you'll end up with a 4x higher impedance and you'll be quite close to the original yoke impedance, probably close enough to work with minor adjustments.

Good luck!

Mike.

Reply to
Remove _ for valid address

What brand and model is this set? Doug

Reply to
Doug

Set fixed! I simply connected the H winding from another yoke in series, and everything seems to work great. Now I just have to find a remote that will adjust the color/brightness/etc, and the set is ready to use. Thanks for your help.

Reply to
Chris F.

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.