what is this wire

[kardenm]

I have  WG 19K7201 monitor.  On the board is a heavy gauge wire which wraps twice around the flyback (armature ??) and is connected to some components on the board.  I had been hearing a loud HF buzz or squeal which disappeared when I slightly repositioned the wire coils.  What is this wire? Why was it squealling?

[lilshawn]

i'm not entirely sure, but i believe it's used by the chassis for timing purposes (it picks up the pulses of high voltage going through the core) it doesn't really carry any current, but its just having a small amount of voltage being induced to flow through it at the same time as the transformer is producing the voltage for the horizontal sweep of the CRT beam.

since it's at the same time, the components that are connected to it likely time the video signal to begin displaying at the the beginning of the scan so the picture is properly on the screen.

if it's squealing, i would think that maybe there is something whose solder is loose and repositioning things, made a better contact.

[Larry]

There are two possible reasons.  Shawn has one.  The other is to boost or reduce one of the low voltage secondary supplies off the flyback.

[kardenm]

I'm dredging up this old post because I just saw Randy Fromm explain it on his youtube video.

You are essentially right lilshawn.  The wire is used to sync the PWM controller frequency with the horiz freq.

I thought that was interesting!