Thank you for posting this. I enjoyed watching the detailed alignment process. I consider electronics repair a sort of hobby and am interested in vintage equipment. Maybe because I'm sort of vintage myself (Ha Ha). Not having a great deal of time to actually get much of a hands on experience, I enjoy being able to at least watch it happen in these sort of videos. Thanks again.
Hello Jay, thanks for stopping by. I am the same way; its enjoyable watching the process that other people show and see how things unfold. Even if it is something I have seen or done before, I usually see something new each time. Also being vintage myself, I recall when this gear was the current state of the art and watching and helping my Dad work on these things. He bought me my first Sams in 1980 to help me with a tube TV I had bought second hand and helped me fix it. I still have the Sams; it is a good memory. Thanks for the comment!
Uh oh, a mystery. LOL Isn't that always the way, you get a set working great and put it back in the cabinet and then nothing! I have confidence you will soon locate the problem. :)
Hello. The SG165 sweeps frequencies and puts out a marker that shows on the scope for 10.7MHz, the IF frequency for FM, as well as 100kHz on either side. So 10.6, 10.7 and 10.8 MHz markers. I adjusted the two IF transformers away from both peaking at 10.7MHz, to having a peak closer to 10.6 and 10.8 respectively. That peak would be lower, however the bode magnitude plot on the scope would show a wider curve, not so sharp, such that they essentially ran together at the top creating the plateau appearance that spanned across 10.7 MHz. See 29:05 timestamp in the video. That gives a more evenly tuned bandwidth and thus I ended up with less distortion, allowing the Frequency to Modulate either side of 10.7MHz at a constant magnitude - rather than going through a peak. It is take a bit of patience and experimentation to get the right form, but the SG165 does a nice job helping. The person who previously worked on the radio aligned the FM the same way AM is aligned, which is to peak a maximum at the IF frequency which is ok for AM, but not really for FM - although it will work, but not sound as nice. I hope that I explained that ok. Thanks for watching and the comment.
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Thank you for posting this. I enjoyed watching the detailed alignment process. I consider electronics repair a sort of hobby and am interested in vintage equipment. Maybe because I'm sort of vintage myself (Ha Ha). Not having a great deal of time to actually get much of a hands on experience, I enjoy being able to at least watch it happen in these sort of videos.
Thanks again.
Hello Jay, thanks for stopping by. I am the same way; its enjoyable watching the process that other people show and see how things unfold. Even if it is something I have seen or done before, I usually see something new each time. Also being vintage myself, I recall when this gear was the current state of the art and watching and helping my Dad work on these things. He bought me my first Sams in 1980 to help me with a tube TV I had bought second hand and helped me fix it. I still have the Sams; it is a good memory. Thanks for the comment!
Uh oh, a mystery. LOL Isn't that always the way, you get a set working great and put it back in the cabinet and then nothing! I have confidence you will soon locate the problem. :)
Ha, yes. But I didn't find the original problem, so I am glad the original fault reared it head again while it was still on the bench. Thanks
What did you do differently to get the fm sweep to show as more of a plateau and less of a peak?
Hello. The SG165 sweeps frequencies and puts out a marker that shows on the scope for 10.7MHz, the IF frequency for FM, as well as 100kHz on either side. So 10.6, 10.7 and 10.8 MHz markers.
I adjusted the two IF transformers away from both peaking at 10.7MHz, to having a peak closer to 10.6 and 10.8 respectively. That peak would be lower, however the bode magnitude plot on the scope would show a wider curve, not so sharp, such that they essentially ran together at the top creating the plateau appearance that spanned across 10.7 MHz. See 29:05 timestamp in the video.
That gives a more evenly tuned bandwidth and thus I ended up with less distortion, allowing the Frequency to Modulate either side of 10.7MHz at a constant magnitude - rather than going through a peak. It is take a bit of patience and experimentation to get the right form, but the SG165 does a nice job helping. The person who previously worked on the radio aligned the FM the same way AM is aligned, which is to peak a maximum at the IF frequency which is ok for AM, but not really for FM - although it will work, but not sound as nice. I hope that I explained that ok. Thanks for watching and the comment.