Quote:
Originally Posted by SpaceAge
I have started to notice the picture size will fluctuate slightly with brightness changes. It's most obvious with news banners along the bottom of the screen. I don't think this is a new issue, just something I've recently noticed since I've been running it a lot lately to keep an eye on corona coverage. The picture is watchable but I'm curious if you experts have any ideas about this before I tear it apart again. It has to come apart regardless because the VCR door flap is jammed shut. I did something wrong last time I reassembled it, maybe a misplaced ribbon cable it blocking it... I'm still learning  . |
Not normal. Any TV of this vintage should show *virtually* no change in size based on normal scene content. I've seen this with low cathode voltage on the CRT crank the brightness to the point of overcurrent shutdown, and they still maintain regulation.
So, if we're talking enough to bury half a banner at the bottom, then it's probably got a regulation issue. If you're setting up your vertical height to juuuuust reach the edge of the phosphor, then you will see a small amount of change with brightness. These were overscanned at least 5% from the factory.
I suspect a lot of banners these days are buried at the extreme edge of the frame because the vast majority of TVs these days are flat panels. TVs without a scan display are not "over-scanned" at all, so broadcasters can put the banners right at the edge of the display and no one will complain.
But, the B+ shouldn't change by more than half a volt from dark to bright. If it's drifting with brightness but is more or less at nominal voltage, look for a lazy electrolytic in the regulator circuit.
As for the VCR, you probably have the cassette door on the wrong side of the door lever. Pull the VCR chassis back, flip open the cassette door like it was taking in a tape (but do not open it past normal). Holding the door open, slide the transport back in and let go of the door.
John
12-28-2019, 01:20 AM
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