|
Turned it on and let it run for most of the afternoon to see what would drift or smoke.
Vertical height, linearity, and hold all drift for the first 30 minutes. Horizontally, it started out with a bit more width, but within a few minutes was back to the same narrow picture as yesterday. Focus is still at one end.
Played with off-air signals (amplified rabbit ears, admittedly suboptimum for this location), found tremendous variation from station to station, especially in color level.
Of course, everthing interacts, but the fine tuning is especially a nuisance. Tuning to the supposed optimum point (just below sound interference in the picture) reduces the sound volume. So, the sound detector must be sensitive to the intercarrier amplitude. Found that the hum/buzz in the audio depends on video content, so this is looking more and more like a complete IF alignment.
Checked out the UHF (won't have any after Feb 17), found it will not make snow through the whole frequency range, so there may be some AGC or other problem.
Went through the background and G2 (screen) adjustments. Could not get the DC reading I'm supposed to on red G-K as a starting point (115 V max, instead of 130). It does make a B&W picture, though for all settings of brightness and contrast.
I think the B+ is OK (by measuring video output voltages), but I didn't find an easily accessible point to measure with the chassis in the cabinet.
Blue dynamic convergence controls seem dead. Red and Green seem to be lacking range. Adjusting convergence coils position didn't seem to make much difference.
Played with purity and improved it, but now horiz centering is at one end and would like to go further.
I will measure the HV at some point, but I found that the convenient lead on my HV meter is just too big in diameter to go in the connector in the HV compartment, and can't be squeezed small enough. Have to rig something.
Need to revisit the AGC setting, turning it down a bit from max improved the color transient response, but makes the picture dim at max contrast.
Now I'm musing whether I will need to replace a bunch of resistors in addition to the recapping.
Well, at least no smoke so far -- As my relatives used to ask me, "When do you think they will perfect color TV?"
|