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#1
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Phil, it might be worth trying the old "seven seconds off & back on" test. Does the raster come back at full width, or is it slow filling out? If unusually slow, are there any peculiarities with the lin during fill-out?
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#2
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This is interesting to me. Does slow recovery point to weak tubes or other things as well?
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#3
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Same principle as the Life Test on a tube tester which drops the heater voltage down. This was followed by the 'tap test' of each tube to show up any arcing (like the damper), intermittent shorts etc. Made service calls more effective with less chance of call-backs. |
#4
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OK, I'll try the seven-second test later today and observe the results.
I spent some time yesterday playing with different values for R86, using a handful of 25-watt resistors that I picked up locally. It is a cumbersome and very slow process, to clip a resistor (or series-ed resistors) into place, slide the chassis back into position, turn the set back on, observe the result, and try to compare the pattern to what you saw before. I tried taking photos with the camera on a tripod, and noting the resistor values for later comparison. Subbing the capacitor values was so much easier with a decade box, where I could keep my eyes on the screen and flip between different values, back and forth, looking at different parts of the screen, etc. Anyway, yesterday's results were not very informative. When I put a crosshatch pattern back on, I realized that the linearity wasn't quite as good as I remembered. I also realized that I had begun with the TV in a somewhat random state -- that is, with the various controls set to produce an image with best horizontal linearity & centering. I had also left in the .22 cap across the width coil. What kind of baseline is that? Perhaps it would make more sense to remove that .22 cap and center ALL of the pertinent controls, then repeat the rigamarole of subbing the cap and resistor values, looking for changes that make sense. There are lots of variables in this equation. In addition to the horiz width and linearity adjusters, you have the horiz centering and horiz drive adjusters, all of which affect width and linearity to some extent. Not to mention the mechanical centering adjusters on the optical box. Does anyone have a clear idea what changes you would expect to see on a perfectly-linear set when changing the value of this damper resistor (R86)? Phil Nelson |
#5
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Some sets that used that big damper resistor (RCA 630?) had taps on the resistor to rough in one of the horizontal adjustments (forget if it was the width or lin) so the control of that name would be in the correct range to work.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
Audiokarma |
#6
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The 630TS factory manual says this is a coarse linearity adjustment: "If repeated adjustments of drive, width, and linearity fail to give proper linearity, it may be necessary to move the tap on R209, which is located in the high voltage compartment. Adjustments of drive, width, and linearity must then be repeated." The parts list describes R209 as: "Wire wound resistor, 5300 ohms, 20 watt; 500 ohms, 2 watt; and 500 ohms, 2 watt." Not sure what to make of that description. Why only 2 watts for the 500-ohm segments? In the schematic, that resistor is drawn with three taps, and the default connection made at the center tap. I interpreted this to mean it's a 5300-ohm resistor, which you can adjust to either 5800 or 4800 ohms by moving the tap. Am I guessing wrong about the resistor construction? Phil Nelson |
#7
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(If the 5300 were 5000, the figures would be exact.) |
#8
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[QUOTE=
The parts list describes R209 as: "Wire wound resistor, 5300 ohms, 20 watt; 500 ohms, 2 watt; and 500 ohms, 2 watt." Not sure what to make of that description. Why only 2 watts for the 500-ohm segments? [/QUOTE] Power in each segment uses the formula P=(I^2)R. Since the resistor section are in series, the same current would go through all resistor sections. The 500 ohm sections are approximately 1/10 the value of the 5300 ohm section; hence, their power handling capacity would need to be only 1/10 the wattage of the 5300 ohm section. |
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