Westinghouse 17TV7C

[Tim]

Originally Posted by Phil Nelson

I think some TVs were deliberately designed with a little overscan so that customers wouldn't constantly call the repairman when components aged and black bars appeared on the edges.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

About 10 to 20% overscan was normal for consumer TVs. There are 2 parameters that were (are) used when framing and inserting graphics on images. "Safe Action" and "Safe Title". "Safe Action" is considered about 90% of the rectangular broadcast image where nearly all sets will display that area to the viewer and not cut it off. "Safe Title" is normally considered as 80% of the image where all sets will display and not cut off the titles or graphics. Some professional and broadcast monitors have a "safe title generator" option so the 80% box will be displayed on screen for proper framing of titles in the studio or post production.

I agree that your set seems to overscan a bit more than this.

Here is an image I lifted from the internet illustrating the 2 parameters that I mentioned.

[MIPS]

The height can be adjusted with a lot of fiddling with linearity and vertical hold but the width has been the problem that's frustrated me for the last two weeks simply because the only control does pretty much nothing at all. Either the circuit was always a really weak one or I simply can't find the fault.

[old_coot88]

In the absence of a width sleeve or an operative width control, there's a coupla ways to reduce width.

1. increase the value of the resistor feeding the screen grid (G2) of the H output tube. This reduces the voltage on G2.
First try about a 5% increase in value of the resistor, and go from there.

2. Add resistance in the cathode leg of the H output tube. Try 50 ohms as a starting point.

The caveat to these methods is that HV is reduced proportionately with the width.