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#1
06-12-2012, 12:33 AM
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It's sweeping the whole screen, but I don't consider the vertical fixed. It's not very stable, and when the sync is far off, it occasionally blinks to a horizontal line as if something (a shorted turn in the output transformer?) was arcing.
By clipping another cap in parallel with C16 (raising its value a bit), I can reduce the height to nearly fit the whole image on the screen, but still with poor linearity. The best compromise between height & linearity doesn't seem too awful at first:  Until you look at a pattern:  I could live with that degree of non-linearity, but the instability really ain't acceptable. I'll keep pokin' around. Phil Nelson 
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#2
06-13-2012, 11:16 PM
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I am happy to hear that the "non-logical" vertical problem had a non-logical cause (the wrong value part); it can happen to any of us. Now you need to re-check the rest of that area because your vertical should definitely have better linearity than in your B&K picture.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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#3
06-14-2012, 01:26 AM
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Yes, in further puttering, I returned R55 and C44 (Sams numbers) back to the values given in the Philco docs. I had tried different values for them at various times, including an alternate Sams value. I also swapped amongst my three 6DR7 tubes until I found which one my set likes best. Linearity and vertical lock are both improved.
  Then I ran through the horizontal & audio alignment procedures and played the set for a few hours. Nice and stable. Those pics are from a DVD player, which has a strong signal and tends to swamp some sets. When I switched to the built-in rod antenna, it worked very nicely, receiving the relatively weak signal from my Blonder Tongue modulator on the opposite side of the house. Not perfect, but I can see light at the end of the tunnel. Phil Nelson
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#4
06-14-2012, 02:56 AM
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Excellent progress!
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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#5
06-18-2012, 03:44 PM
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After a few more tweaks, I'm declaring this one finished.
 Part of the difficulty I had with vertical linearity is that someone had adjusted the vertical centering as far off as it could go (perhaps to compensate for some aging component in the past). With that back in a sensible range, it was a piece of cake to make the vertical correct using the other controls. I always feel better when controls are somewhere in the middlin' range rather than maxed out. There's an article, too: http://antiqueradio.org/PhilcoH3412L...Television.htm In researching, I found Philco's original patent drawing for the tabletop cabinet:  Interesting that the original concept had more knobs on the front, and a slanted control panel. On to the next project! Thanks again for the advice. Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html P.S. I'm missing an end cap for one of the support arms. If anyone has a spare, contact me at http://antiqueradio.org/contact.htm . Last edited by Phil Nelson; 06-18-2012 at 03:49 PM.
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#6
06-19-2012, 02:09 AM
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Nice job, Phil.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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#7
06-19-2012, 12:01 PM
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And so concludes another neat resto adventure and accompanying write-up. Great job, Phil (as per usual).
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Hybrid Mode
