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Pin 4 of IC10 appears to switch IF I have the levels from the phototransistors at a very critical point. I was looking at the signal coming from each phototransistor going into IC11. One is a very nice square wave and changes with clockwise and counterclockwise rotation of the tuning knob. The other looks like there is no sharp rise time on the square wave. The leading edge is curved quite a bit. I can make it better, and it will tune up fine, and the brake releases, but it doesn't tune down. There is a very touchy point in adjusting the 3K pot where it will tune up and down. At this position the brake does not release if you spin the dial fast, but it does tune up and down even with the crappy looking input from the phototransistors. I may have a bad phototransistor. Not good since I don't think they are available any longer. I will have to find my antenna to see if it is actually receiving when I tune up and down. I can check FM with my handheld radio. I may have to find another parts set to make one work.
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