VT-73 Motorola Sound IN video?

[old_tv_nut]

Any progress on finding the sound in pic problem?

If you have a scope, you can look for sound waveforms on pin 6 of V11B, 2nd sync clipper (second half 12SN7). If there is sound there, then it must be a problem with C38 or the connections to C38.

I also see a weird three-way connection to the bottom of R29, with two leads going to the same electrical point in the sound section above. I wonder if this is a mistake in the SAMS. Maybe the horizontal line should be broken between these two leads and not to the right of them.

[koviatt]

I really appreciate your followup. I will poke around on V11B and see if I have sound there. Like I said, I can get a nice picture OR I can get decent sound, but not both at the same time.

[koviatt]

Originally Posted by old_tv_nut

Any progress on finding the sound in pic problem?

If you have a scope, you can look for sound waveforms on pin 6 of V11B, 2nd sync clipper (second half 12SN7). If there is sound there, then it must be a problem with C38 or the connections to C38.

I also see a weird three-way connection to the bottom of R29, with two leads going to the same electrical point in the sound section above. I wonder if this is a mistake in the SAMS. Maybe the horizontal line should be broken between these two leads and not to the right of them.

I followed your instructions. What initially threw me off was that the cap is C3 B (not 38). So I scoped that connection on pin 6 and had a lot of noise and audio on the pin. I decided to replace the new cap. That fixed it. Good work. Now I can do an alignment. I have the sams and instructions, so this weekend I will try again. I have it pretty close, but I am still getting some "vertical buzz" in the video. I know this is typical of many early sets. I can find a happy medium of audio gain and near elimination of the buzz. Maybe the alignment will address some of this. Thanks so much. Another lesson on questioning your assumptions ("I replaced that cap already...").