On 2017/07/04 5:44 PM, wrote:
ive got a tovis mtg-1901cn cga color monitor. in use, or with a test pattern, the image starts out perfectly at the top. as you move down toward the middle , it gradually starts to compress the image, with more compression the closed you get to center. and when it gets to mid screen, its a full vertical collapse. bright while line across the center, with no image whatsoever in the lower 50% of the screen. also sold as a vision pro .

battery voltage is good at 123, 12v and 24 v are good. 123 volts at the flyback.
the vertical output ic is a LA7833. pin 6 has good 24 volt supply, and pin 2 ( output) is a nice 24 v square wave. i recapped the monitor, and the image is exactly the same. now im stuck.

thanks


Your vertical circuit is missing the bottom deflection half of the
vertical circuit. If the vertical driver is an IC, replace it, if it is
a pair of transistors then I would suspect the transistor pulling to
ground (typically the lower of the two on schematics) is the one at fault.

The vertical drive is just a very slow audio amp, apply audio amp
service methods.

John :-#)#

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