Zenith 19EC45 Vertical Problem?

[kx250rider]

Originally Posted by jblmar

Thanks to all for your help. The board is a 9-147. C701 measured open. The problem is still there. I can't check the set with the 9-92 schematic since they are different. Anyone have or know where I can get the 9-147 schematic. I don't have the time to trace the foil side, so the schematic would be handy.
Thanks again to all for your help.
Ron

I'd try the Sams for a later chassis; F or G (25FC45, etc). I can't remember where the cutoff is for the changeover to 9-147, but it was early in the Chromacolor series.

Charles

[jblmar]

Thanks Charles. I'll give them a call.
Ron

[jstout66]

Charles, was the 9-147 a sub to use for the 9-92, or did you HAVE to use the module the set came with? and Ron, I've got those modules so hollar if you have any problems repairing yours. Jamie

[kx250rider]

The 9-147 is an update, to go in all sets that had/have the 9-92. It's a direct plug-in swap.

Charles

[jblmar]

Hey Charles. Over the weekend, I'll check the voltage going to the board. When the set is first turned on, the bottom half of the screen is black. Not as black as the top, a shade lighter. As it warms up, it clears up. I need to find the source of that problem first. That may or may not be the board.
Ron

[jblmar]

Had a look a the set toda and found the following,
Measured voltages to vertical board. All measured o.k.
With the back removed, the bottom of the screen remains black.
When I replaced the back panel, the picture clears up in about 15 minutes.
Remove the back and the problem is back!
Ajusted the vertical size (Vr 717). Screen size is now normal.

The problem is COLD related, not heat related. I'll ceck all the boards for cold solders.

Ron

[andy]

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[jblmar]

I tryed that, Andy. The problem is that the set cools faster that I can remove the back panel. With the back off, it never reaches the temperature for the problem to be visible on screen. I'll check all electrolytic caps on the video board.
Thanks for your input.
Ron

[jstout66]

it has GOT to be the vertical module

[andy]

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[jblmar]

The screen area was smaller. The top and bottom were missing about 2". Voltages to the vertical board were correct, so I adjusted VR 717 (vertical size) and that corrected that problem. The remaining problem is that on set turn on from "cold" the bottom of the screem is black (about 1/5 of the screen), but you can see some picture through the black area. It takes about 15 minutes for the condition to clear up, slowly, the black area lowers until the screen is normal. Afterwards, the screen is full size and works fine. When the set cools after turn off, the problem returns.

jstout66, I cooled the vertical board with no return of the problem after the set heated up. That set is difficult to do that with since the ac plug needs to be pulled before removing the back. By that time, the set cooled enough for the problem to return.
Ron

[jblmar]

Just an update. As of today, I haven't had the time to work on the set. Thanks to all who responded. I'll keep you posted.

Ron

[kc8adu]

take the clip out of the cheater cord.then use a hairdryer to warm it up faster.

[jblmar]

Thank's kc. The problem is when the set is cold, the botton 1/4 of the screen is black. When the set warms up after 10-15 minutes, the picture is fine. The opposite of a thermal intermittent.

Ron

[andy]

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