Quote:
Originally Posted by Tom Albrecht
Made some further progress on the CT-100 after some time away from it. Two key findings:
1. I actually get more red with the red screen turned DOWN, not up. I modified the circuitry to lower the voltage range of the screen controls, and this actually helped. I don't understand why this is the case. Anyone have an understanding of how the screen control is behaving this way? I've confirmed that the voltage at the CRT socket goes up and down with the screen control setting as expected.
2. While building the cathode follower into the chassis more permanently, I happened to spot check some components under the chassis, and found the choke on the plate of the Q synchronous detector was open. I'm sure I checked this coil when I first restored the chassis a few years ago, but undoubtedly this coil opened in the mean time. This was confusing my interpretation of what was going on with the red. I'm surprised at how well the color worked with this choke open, but it's certainly much better now. Also replaced some drifted resistors while I had it on the bench. Not a bad idea to pull the chassis on a set like this every few years to catch the newly deteriorated components.
I've now got the cathode follower built in to the chassis, hiding inside the cage where the selenium rectifiers once resided. This leaves the chassis looking relatively original. The cathode follower is worth its weight in gold for enhancing the red on this set. It's officially "daytime watchable" now, which makes it a lot more fun to have around. Here are some daytime viewing pictures. Blinds are closed (with sun directly on the windows, which still lets a lot of light into the room).
Here are some quick screen shots. Didn't have nice reds like these in the daytime until now.
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That looks extremely nice Tom! I think your screenshots are the first I've found that look remarkably similar to how a working 15GP22 looks in person. Do you do anything special when snapping screenshots?
This also provides a bit of hope to anyone with a rather anemic looking 15GP22, provided of course it's still under vacuum.