Riddled TV Repair Forum

celsomaiolo · Joined: 03 Nov 2008 Posts: 2 Location: Toronto

Hello, I have a couple of Sony PFM-42B2 plasma displays that I'm having problems with and hope that someone may be able to offer advise. I'm familiar with PFM-42B1 problems, for example X-SUS or Y-SUS boards going bad and both of these PFM-42B2 needed X-SUS boards replaced. Once replace both panels display correctly and life is pretty good. However on closer inspection there is pronounced screen noise on both of them, one worse than the other. I can best describe the noise as a vertical shimmer on the picture to the point where the very left or right edge of the screen is not a crisp vertical line but like a "saw" with fine teeth. I have heard that beside X-SUS and Y-SUS that these units also had flakey power supplies? Specifically the APS-179 board. There is a Sony tech note describing the addition of an additional bypass cap to quell noise on the Standby 5V supply rail but but supplies have the additional cap. If anyone has any hints I would appreciate the help. Thank you.

Google

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

Whenever you replace the Y-SUS or the X-SUS boards it is important to adjust the Power supply Vscan, Vset, Vs etc etc. Failure to do so can produce a poorer than normal picture as in under or over diffusion as the new boards usually draw different levels of current.

There is a common symptom among many manufacturers that is known as Under Diffusion and Over Diffusion.

Under diffusion = Dark Pixels in bright areas of the screen
Over Diffusion = Bright Pixels in the dark areas of the screen
Blue smear on left edge of screen that can creep from left to right as levels get too far off.

Make sure that the power supply is correctly adjusted. If the problem still exists reduce the Vs voltages by 10VDC for Under diffusion and increase 10VDC for over diffusion. I do not remember which way for the smear.

The proper voltages for the power supply is printed directly on a sticker on the panel.

Hope this helps

Jesse

celsomaiolo · Joined: 03 Nov 2008 Posts: 2 Location: Toronto

Appreciate your reply and suggestion. I will definitely check all the supply voltages to make sure they are within specification.

Really appreciate your help

Celso