#31
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Quote:
Since it had been suggested the last IF tube may be responsible, think for a moment the consequences in the change in the IF response which would result in the ringing or ghosting. A peak in the IF response would occur and when the fine tuning is changed, the video band would sweep the peak in the faulty IF response so that the frequency of the peak in the demodulated video band would change as a consequence. In other words, the ghost spacing would change as the fine tuning is adjusted. If adjusting the fine tuning does not change the ringing spacing, then the problem must be after the second detector eg in the video amplifier. As has been pointed out, a badly terminated delay line would alter the baseband frequency response. Last edited by Penthode; 12-27-2015 at 01:22 AM. |
#32
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Did you try a direct injection of a composite signal at the 1st video amp? that should clear everything (tuner/IF/detector diode) before it. divide and conquer.
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#33
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Swung by last weekend, the ghosting is changing with adjustments to the fine tuning so I think this is going to be either an IF alignment or tuner link issue. We had to get better convergence before delving into that though, and found that the blue horizontal pot did nothing. It wound up being burned up and open in places, so Larry is looking for a new 120 ohm wirewound pot to replace it. Once that's fixed, we can solve the ghosting problem.
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#34
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Just curious, how many cases of last IF ringing have you actually encountered? I've seen it in 3 stage strips as well as the oddball two stage (6EH7, EJ7) strips). |
#35
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I've decided to just live with it. It has a pretty good picture otherwise. I have to remind myself that this is a 56 year old tv. I'm just glad it functions when I turn the set on.
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Audiokarma |
#36
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I do think it could be a little better, trouble is making it better means a complete convergence setup. I don't think it's worth all the effort, it's good enough now.
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#37
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I know delay lines seldom fail, but just for curiosity's sake try putting a clip lead across the 2 ends of the delay line. Don't clip anything to the ground side. and see if the ringing (or ghosting) disappears. I battled this exact problem for months before I found it. The "new" delay line solved the problem. I guess I'm really curious myself if that's your problem or not.
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#38
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It's not the delay line, I've seen it in person.
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