[NJARC] Predicta Help Needed!

[w2wiq1 at juno.com]

HI:
TO ME THIS SOUNDS LIKE A COMMON PICTURE TUBE PROBLEM OF HEATER TO CATHODE SHORT AS THE TUBE WARMS UP. I RECOMEND THAT YOU TRY TO FIND A PICTURE TUBE ISOLATION BOOSTER.IT WILLALSO HELP THE AGED PICTURE TUBE.I STILL SEE THEM AT IMES ON EBAY. THEY PLUG INTO THE SOCKET FROM THE CHASSOS AND HAVE LEADS WITH A SOCKET TO PLUG ONTO THE PICTURE TUBE.

WALTER-W2WIQ

---------- Original Message ----------
From: "George B. Shields, Jr." <george-shields at msn.com>
To: NJARC Listserve <njarc at mailman.qth.net>
Subject: [NJARC] Predicta Help Needed!
Date: Tue, 25 Aug 2009 00:50:08 -0400

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Hi Guys,OK, maybe I need to recast my help net a little:  I need the advice of someone who'se worked on a Philco Predicta(s), either recently or perhaps extensively in the past.  I've done a bit of fooling around and have found that the problem in my Danish Modern Predicta is not actually the absence of the 400 volt boost.  It seems deeper.
The chassis is a transformer model type 10L43A, the same as in  the 17" metal tabletop princess models. 
The set when powered up operated well for about 1 minute.  At that point, the picture went to a white raster - good vertical and horizontal at first, but after awhile the horizontal sweep decreased from the left side of the screen.  After that point the center of the picture tube became dark with brighter raster more to the periphery of the screen.  Subsequent power ups would sometimes show a full screen raster and sometimes the screen will remain dark and only slowly light up with a raster. At other times it will light up with a full raster rather quickly. By tube swapping I haver managed to get a full raster back, but there is still a darkish area in the center of the screen.  This can be adjusted out by fooling around with the width control as well as the horizontal frequency control.
The audio is perfect, no problem there.  This seems to indicate that everything is functioning OK up to the video output tube, where the audio takeoff occurs.  
The problem seems to be somewhere after the output of the video output tube.. Another thing: it seemed that before the set failed, focus was better around the periphery of the screen image and less at the center of the screen.
Frustrating part is that this chassis was thoroughly gone over by a pro some time before I acquired it.  All new caps, mostly new resistors, and all very professionally done, no raggedy work anywhere. 
Anyone run into this sort of problem before with a Predicta or other model television set for that matter?  Advice, thought or leads would be appreciated!
Thanks,-George-

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