Quote:
Originally Posted by Smoky Pond
. . . . . it looks like the RF is weak as well.
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I'll repeat:
On this set the
Contrast Control is the AGC control.
Find where the trouble is and fix it, first.
The contrast control should vary the AGC voltage. Find out why it does not.
As Smoky Pond said, it does look like a tuner issue, too, but you cannot tell for sure until you fix the video IF section.
After you get the contrast and brightness controls working, and have confirmed that your HV is up to specs, you can trouble shoot the focus issue:
First, you will need to find an RCA schematic diagram, as the light barrel is not the same one that is in the Sams, which was the 1947 to 1948 version. The focus and alignment methods are different. The 9PC41 only carried the 1949 light barrel. (I've seen a few late production 1948 sets that carried the "1949" barrel.)
You first will get the electrical focus as sharp is possible. You will need to be able to get it to go out of focus on both sides of the best focus. Then do the mechanical focus, and go back and repeat the electrical. This process is continued until no improvement is seen.
Warnings:
Make sure the yoke is level before you start, as yoke adjustment can shift the electrical focus.
An very easy assembly mistake to make is to put the donut lens back upside down after cleaning in the 1949* model. The flat side goes up. If this lens is inverted, you will never get good mechanical focus.
Clean this Lucite donut lens very carefully, as it scratches easily.
* I've never worked on the older model barrel
James