Half a screen on a WG K7500

[pcjohn]

I came across an interesting repair today.

A K7500 with a fried flyback. Unfortunately the arc burned into the
G2 and focus leads.

After repairing the chassis I found that only the right half of the
screen is visible. The left half is dark (horizontal deflection,
not vertical).

After rechecking the chassis and finding nothing wrong, I tried
a known good chassis and got the same results.

Can I assume that something in the tube itself is bad ? I don't
think this is a yoke problem.

JD

 

[mecha]

oh no, that's the wire you wrap around the core of the flyback. you have to do it a specific way, and it's going to be a challenge for me to find my picture of how to do it.

do you have another original K7500 on hand?

 

[pcjohn]

Hmm, that's interesting. Do you know if that wire is also on a K7400 ?
I have one of those at my regular job.

JD

oh no, that's the wire you wrap around the core of the flyback. you have to do it a specific way, and it's going to be a challenge for me to find my picture of how to do it.

do you have another original K7500 on hand?

 

[mecha]

K7400 didn't have it. I'll have to scrape at work but I might be able to find other K7500s.

it's a black wire that runs from either end of the flyback, that wraps around a very specific way.

 

[mecha]

check it out. the right side of the wire goes around the part of the core closest to you, wraps around, and comes out to where it goes on the left side. I'm guessing you probably disconnected it on the right side of W190 in front of the flyback.

 

[pcjohn]

It's not disconnected, however the loop around the core
of the flyback is closed. It goes around the core, then
wraps around itself before going back to the board.

I won't be back at the location until next Saturday, so
I will check it out.

JD

check it out. the right side of the wire goes around the part of the core closest to you, wraps around, and comes out to where it goes on the left side. I'm guessing you probably disconnected it on the right side of W190 in front of the flyback.

 

[mecha]

I was looking at other threads to see if I could find my old picture cause I swore I shared it in the past. it's possible to loop it the wrong way.

I'll post my epic fail picture when I get home later. I wasn't sure if I'd be able to get attachments to work from the phone browser, that's why I PMed you before.

 

[pcjohn]

You were correct, sir !

Matched the wire to your picture and it now
works perfect.

Many, many thanks !

John

oh no, that's the wire you wrap around the core of the flyback. you have to do it a specific way, and it's going to be a challenge for me to find my picture of how to do it.

do you have another original K7500 on hand?

 

[Onji]

Old thread bump? Sure is! I was banging my head against the wall with this one. @mecha 's pic saved the day.
The left half of my screen just black, and thought I screwed something up width cap wise, but nope I just had the stupid black wire going around the core incorrectly. I matched the pic, and all is well. So thanks @mecha !