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.

"Chris F." wrote in message
...
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.



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

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

Chris
"James Sweet" wrote in message
news:ZBroe.4971$J73.2691@trnddc05...

"Chris F." wrote in message
...
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.



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

May consider the value of the yoke ringing caps in the input and return
circuits??
"Chris F." wrote in message
...
I was just thinking the same thing, I will give that a try and see what
happens.

Chris
"James Sweet" wrote in message
news:ZBroe.4971$J73.2691@trnddc05...

"Chris F." wrote in message
...
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.



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

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

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.

What brand and model is this set?
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.

"Doug" wrote in message
ups.com...
What brand and model is this set?
Doug

Congrats Gov.
"Chris F." wrote in message
...
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.

"Doug" wrote in message
ups.com...
What brand and model is this set?
Doug