[TechAssist] Re: Panasonic horizontal tearing and dull picture (FIXED)
- From: MDileo0000@xxxxxxx
- To: techassist@xxxxxxxxxxxxx
- Date: Thu, 18 Sep 2003 11:11:42 EDT
CORRECTION :
The ABL voltage was running -80vdc to -280vdc.
In a message dated 9/18/03 11:02:03 AM Eastern Daylight Time,
MDileo0000@xxxxxxx writes:
> Panasonic CTP-2780SF, AEDP218 chassis. Replaced R551, C563
>
> This set had varying unstable horizontal sync during bright scenes,
> blooming, poor grayscale tracking and gun flare. Resoldered several cold
> solder pads
> on both primary and secondary side of the SMPS. This restored the 141volt
B+
>
> source which was fluctuating between 131~135 vdc. This partially fixed
> things,
> but aggravated the horizontal sync and blooming problems. And now it was
> shutting down during bright scenes. I checked the ABL source at pin 3 of
the
> FBT. It
> was running up and down, 80vdc to -280vdc, causing ABL filter (C563,
> 4.7mfd@160vdc) to open. I found R551 (10k@1/4wt) open. This resistor
> provides a
> positive offset tracking voltage keeping the ABL line low enough to
prevent
> the hold
> down sensor (pin 14, IC301) from activating.
> This set was in another shop and misdiagnosed and have gone out of
business.
>
> As a result there were many geometry presets "tweaked and diddled" that
had
> nothing to do with this failure. None of it was too bothersome to setup
> correctly, but added to the final bill. The customer is smiling and that's
> all that
> matters.
>
> Dominic DiLeo
> Atlantic TV
> Freeport, Maine
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