CTC-9 Winslow

[Zsuttle]

I injected a signal into the 1st video amplifier and was able to get a color unlocked, almost synchronized image. Horizontal and vertical sync were very finicky. Somewhere in the IF amplifier section, it's not getting through.

Unfortunatly I don't have any modulators capable of the necessary bandwidth. I may have a B&K 1077B laying around somewhere, which if I recall is able to do the 44MHz IF.

[Zenith26kc20]

There is a hidden bumblebee in the IF section under the removable metal shield that gets leaky. Make sure you change it.

[Zsuttle]

After poking around in the IF section, I noticed a few things. The picture detector was testing weirdly. Even after pulling it, it was still giving me strange readings. The sound detector checks as I would expect it to. Someone had already replaced both the picture detector and sound detector, not sure when. Pretty much any germanium diode should work right? I have a couple of 1N60s laying around.

I also found a bad ceramic C318, I think unrelated to my picture problem, but the cap was reading around 7kohms or so. Pulled it, still tested the same. I haven't seen ceramics fail like that before. Better to use a 50V or a 3kV? The 3kv is close to the original size (versus the tiny 50V), but not sure if there's a problem using that high of a voltage for such a low voltage application.

Lastly, I found that I somehow replaced R314 a 12k resistor with a 1.2k resistor. I somehow had them in the wrong drawer and didn't catch it when putting it in.

Fingers crossed when I fire it up tomorrow

[Alex KL-1]

Originally Posted by Zsuttle

After poking around in the IF section, I noticed a few things. The picture detector was testing weirdly. Even after pulling it, it was still giving me strange readings. The sound detector checks as I would expect it to. Someone had already replaced both the picture detector and sound detector, not sure when. Pretty much any germanium diode should work right? I have a couple of 1N60s laying around.

I also found a bad ceramic C318, I think unrelated to my picture problem, but the cap was reading around 7kohms or so. Pulled it, still tested the same. I haven't seen ceramics fail like that before. Better to use a 50V or a 3kV? The 3kv is close to the original size (versus the tiny 50V), but not sure if there's a problem using that high of a voltage for such a low voltage application.

Lastly, I found that I somehow replaced R314 a 12k resistor with a 1.2k resistor. I somehow had them in the wrong drawer and didn't catch it when putting it in.

Fingers crossed when I fire it up tomorrow

About the diode, any regular signal Ge diode can work here (almost any)...
The cap, if is a decoupling, I don't see too much trouble in using higher voltage value. Only ones for tuning or coupling can be much more critical.