Help appreciated - Image size fluctuates on direct view CRT

[bosoxchamps]

I just sold a TV (Panasonic 36" flat screen HDTV set) to someone that
was working perfectly while at my home. The individual who bought TV
from me did see the unit functioning in my home with no issues using an
HDTV tuner. Upon the individual getting the set home and hooking it up
the picture size fluctuates from getting smaller to slightly larger.
This happens even when the TV is not hooked up to any input source and
just the menu is displayed. The menu gets larger and then smaller. I
have not seen this myself but I think I am accurately describing what
the individual told me.

Does anyone have any thoughts?

Thanks,
Mike

 

[kip]

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.

 

[3T39]

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

k> ??>> I just sold a TV (Panasonic 36" flat screen HDTV set) to someone that
??>> was working perfectly while at my home. The individual who bought TV
??>> from me did see the unit functioning in my home with no issues using
??>> an HDTV tuner. Upon the individual getting the set home and hooking it
??>> up the picture size fluctuates from getting smaller to slightly
??>> larger. This happens even when the TV is not hooked up to any input
??>> source and just the menu is displayed. The menu gets larger and then
??>> smaller. I have not seen this myself but I think I am accurately
??>> describing what the individual told me.
??>>
??>> 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: [email protected]

 

[bosoxchamps]

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

 

[3T39]

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: [email protected]

 

[Yukio YANO]

I just sold a TV (Panasonic 36" flat screen HDTV set) to someone that
was working perfectly while at my home. The individual who bought TV
from me did see the unit functioning in my home with no issues using an
HDTV tuner. Upon the individual getting the set home and hooking it up
the picture size fluctuates from getting smaller to slightly larger.
This happens even when the TV is not hooked up to any input source and
just the menu is displayed. The menu gets larger and then smaller. I
have not seen this myself but I think I am accurately describing what
the individual told me.

Does anyone have any thoughts?

Thanks,
Mike

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

 

[Smitty Two]

I just sold a TV (Panasonic 36" flat screen HDTV set) to someone that
was working perfectly while at my home. The individual who bought TV
from me did see the unit functioning in my home with no issues using an
HDTV tuner. Upon the individual getting the set home and hooking it up
the picture size fluctuates from getting smaller to slightly larger.
This happens even when the TV is not hooked up to any input source and
just the menu is displayed. The menu gets larger and then smaller. I
have not seen this myself but I think I am accurately describing what
the individual told me.

Does anyone have any thoughts?

Thanks,
Mike

I had an old trinitron for many years that would pulse in rhythm with
the washing machine. I took it to be line voltage fluctuation.

 

[Mike Berger]

I'd suspect low line voltage or poor regulation (he's at the end
of the power drop in the neighborhood) before a problem in the TV.