Panasonic VSUS low and trim pot maxed out.

[BigPete]

Hi,

I have a tv where VSUS has to be 189V +or- 2V. The highest I can get it is 181v. I turned the trim pot to get the voltage up but it slowly drops again.
What is the problem? Leaky caps or something?
Also two 450v 1uF film caps are noisey occasionally in the power supply. I replaced them but they still hiss. They can be located on page 78 of the service manual in the link below. They are c611 and c610.
Any help would be appreciated.

Thanks

Pete

[Ltank]

Re: Panasonic VSUS low and trim pot maxed out.

Most sets have some noise but it should not be excessive. As far as the lower voltage it could be a heavy load or as simple as a bad trim pot. With power off and unplugged you can measure the trimpot total resistance and the resistance of the wiper. Have you tried cleaning it with cleaner and sevral passes on the adjust it cw and ccw then apply power and readjust.

[tom66]

Re: Panasonic VSUS low and trim pot maxed out.

Does vsus rise if you unplug the SC and SS boards?

[BigPete]

Re: Panasonic VSUS low and trim pot maxed out.

With the tv unplugged during the night, VSUS with both sc and ss boards disconnected was 200v.
With boards connected it was 200v. After leaving the tv running for 15minutes, VSUS dropped to 180v. With both sc and ss disconnected, VSUS still at 180v.
With the trim pot fully cw it is 71kohms, fully ccw is 5ohms. Didn't clean it but turned it cw and ccw multiple times. Part states that it is a 50kohm trim pot. Would increaseing it to 100kohm be wise?