Help appreciated - Image size fluctuates on direct view CRT

Sounds like maybe in transit something possibly dry joints have been disturbed and now are giving trouble. remove the chassis and with a Mag Glass inspect for bad solder connections.

Hello, kip! You wrote on Fri, 24 Mar 2006 12:50:54 -0500:

??>> Does anyone have any thoughts? ??>>

??>> Thanks, ??>> Mike ??>>

Picture size variations are usually caused by voltage regulation faults, dried up caps in the power supply section spring to mind first, but no one could be more specific without more info. Pete

With best regards, 3T39. E-mail: snipped-for-privacy@hotmail.com

Kip actually responded with suggesting the soldier joint area being a potential culprit. I am the original poster - bosoxchamps

Thanks for the info. Any guess as to how moving the TV might have introduced such a problem. I can't see how you could damage anything in the power supply section during moving the TV.

Thanks, bosoxchamps

Hello, bosoxchamps! You wrote on 24 Mar 2006 13:18:37 -0800:

b> Thanks for the info. Any guess as to how moving the TV might have b> introduced such a problem. I can't see how you could damage anything in b> the power supply section during moving the TV.

Obviously I can only guess from here, but rough handling can shake a connector or even crack a board. As a previous poster said, maybe a bad solder joint was made worse. It seems certain that an incident happened in transit, and it's just that given the symptoms (fluctuating picture size ) my first thought was voltage regulation. PS if voltage regulation is the issue, I would expect the size variations to co-incide with bright picture content ie: when there is a larger area of bright picture the current demand goes up and if the regulation is poor the PSU can't cope so the scan is reduced. Best of Luck, Pete With best regards, 3T39. E-mail: snipped-for-privacy@hotmail.com

Is there an external field present !! I once solved a "breathing display" by turning off a large Blower Motor mounted on a wall NEXT DOOR !!

The Scan rate is slightly off-set from the National Grid for technical reasons and as a result the Electromagnetic field from a line operated Fan motor will cause a CRT "breath" ie show a slow slight shift in response to an external magnetic field. A CRT is an extremely sensitive electromagnetic field detector. If the display is swelling and shrinking ?? a High Voltage or Focus Problem ??

I would check first, by moving the screen to a different part of the Room. This is a Flat Screen HDTV ?? Does it operate differently than a conventional CRT?? Does it use electro-static or electro-magmetic scanning. Or does it use a XY matrix like LCD display.

Yukio YANO