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#181
10-20-2016, 09:29 PM
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I tried using the 369 but it won't work. I still have the waveform as above. The frequency of the waveform is still off by the same amount. I'm at a loss.
What determines the frequency of the waveform? If I knew, then maybe I could change it by changing a component or something like that. I know if I had a better grasp of the theory behind the IF circuits I might be able to figure this out. IIRC, Dennis Carter goes into theory on the IF sections of a very similar Admiral chassis. I'm going to watch those few videos and see if that will help. https://www.youtube.com/watch?v=m1xVe1_e5bY Starts at 4:16 Last edited by Crist Rigott; 10-20-2016 at 09:32 PM. 
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#182
10-20-2016, 10:20 PM
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It's a bandpass filter and the adjustable coils determine the frequencies that get through. You don't need to change any components. You need to adjust the slugs so they let the right frequencies through. What exactly happens to the response curve as you adjust A1 through A4 ? The response curve should distort and shift around. You're going to need to adjust all four to gradually shift it over and get it looking like it should.
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#183
10-20-2016, 10:41 PM
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Quote:
I'll tweak them to see if I can get the right shape at the right freq. Thanks for hanging with me on this.
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#184
10-20-2016, 10:50 PM
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Right that's what should happen when you adjust one coil. Adjust A1 so that one side is bigger and the other smaller. Then move on to A2 and adjust it so that they level off. The response should be shifted over now.
Last edited by bandersen; 10-21-2016 at 08:32 AM. Reason: fixed typos
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#185
10-21-2016, 02:04 AM
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Bob and everybody,
I did it! My curve doesn't quite look like the one in Sams, but close. What I did was look at the curve from my AMC 116T that I just did and it didn't have a large flat in the curve. I never touched the IF's on that TV. Sorta for a reference. I then hooked up the Admiral and using the generator and VTVM, I again peaked the 4 coils. Then on to the 369 and O'scope. From here I did just what Bob said to do. Adjust each coil and finally got this curve. I also spent some time doing some little tweaking till I got the pips where they were supposed to be. Also the curve bandwidth and shape. Bob was right, I had to go back and forth among all 4 coils and at times it was a bit frustrating. But I knew I would get it at one time the 24.3 pip was now lower when before it was higher. This gave me the indication that what Bob said about moving the peaks to get the pips where they needed to be. I suppose I could have tweaked a little more here or there, though I'm not too sure. I concentrated on getting the pips on the curve in the right position and frequencies. Here are my results. The pips start at the left of the curve and work their way to the right and to a lower frequency. I flipped over my curve printout (from Riders) and traced the curve and markings just to keep from going nuts. I did hook up my DVD player and sure enough I have good video! I tweaked the audio a bit and the rest will wait till tomorrow. A big thanks to Bob and the others who helped me through this. I learned a lot and next time it will be a lot easier!      
Last edited by Crist Rigott; 10-21-2016 at 09:26 AM.
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#186
10-21-2016, 08:33 AM
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Congratulations! I'm glad you got the hang of it
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#187
10-21-2016, 09:28 AM
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Thanks Bob. At times it looked impossible. Thanks for keeping me going.
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#188
10-21-2016, 02:57 PM
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That's looking very good. If you wanted too I'm sure you could tweak your two humps a little further apart and regain that slight dip and flatten the pass band. Here's the video IF of an Admiral 20Z1 chassis(very similar to your sets IF) that I aligned using an HP digital sweeper complete with 5 digital markers simultaneously intensity modulated utilizing the Z axis input on the scope. Crazy overkill but very fun to play with.
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#189
10-21-2016, 03:05 PM
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Quote:
EDIT: the link doesn't show up. EDIT EDIT: I removed the img in brackets and now the link shows up. EDIT EDIT EDIT:The link doesn't work. http://i452.photobucket.com/albums/q...g?t=1476991455 Last edited by Crist Rigott; 10-21-2016 at 03:09 PM.
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#190
10-21-2016, 03:11 PM
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Kevin,
I was thinking of tweaking it a little more to see if I can get a flat and 2 humps. It'll depend on the mood I'm in.
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#191
10-21-2016, 03:20 PM
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Bottom line is if it looks and sounds good don't mess with it, unless of course you enjoy banging your head against the wall, which I tend to favor most days.
 Not sure what's up with the link, it should show a picture as part of the post. It's working for me here.
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#192
10-21-2016, 03:41 PM
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Yup, the picture shows up now.
I thought there would be a link to the video showing you doing the alignment.
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#193
10-21-2016, 03:42 PM
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That is a nice curve! Hoe did you get the 5 pips?
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#194
10-21-2016, 04:20 PM
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The HP 8662A actually has 5 programmable markers. Every time it gets to a marker frequency it sends out a signal that modulates the Z axis(brightness) of the scope trace. So what you are seeing is it steping through the sweep, and the marker frequencies are simply brighter points on the sweep, not really a pip.
[edit] Here's a close up of that same scope screen shot so you can see how it's actually a series of dots. 
Last edited by Kevin Kuehn; 10-21-2016 at 04:55 PM.
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#195
10-21-2016, 07:00 PM
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Now that's cool. A lot better than my $10 Eico 369, that's for sure!
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