|
Well, the resistor is replaced, adjustments that can be done without
a picture and needing bottom access have been successfully completed,
its back in the cabinet and I went through the purity and B&W setup
things and they seem to work Ok. The B&W picture is a nice 6000K. Purity is
excellent.
I can get a good ordinary color picture. But I don't know how
to adjust the I gain exactly, as the instructions don't
tell how to do it without I-Q bars, which I don't have.
Does anybody have a download that I can use to make
an I-Q bar DVD? Oh! I can do it with Photoshop as I have a player
that can play stills. But can it output composite from stills?
If anybody has one, I'd like a copy.
I carefully examined the frequency response of all the video and color sections.
All were exactly to spec except the Q output. Its supposed to
be only a little down at 0.5 Mhz (80% response there) and it was
in fact at 80% at about 0.15 Mhz and at 20% at 0.5 MHz.
I tried the two new 6.8 mH coils I had purchased in place of
the white one (which, of all the white ones, showed the least
blue copper corrosion). The old one had a very low Q. The new ones
were much higher out of the circuit, and still too high if
clipped in with clip leads and them sitting on my (glass) workbench.
But soldered in, near the metal chassis, they were both "just right"
with a peak at 0.43 Mhz at 85% the response at DC and a small dip
at .25 MHz, and excellent transient response. The I response
is stunningly good ... actually a little flatter than in the RCA
publications, as is the Y.
Now the bad news, as Phil Nelson suggested in the other thread
in the Color TV forum. As I said, purity is perfect. Convergence
and focus is abysmal. Well, there is one setting where focus is
really excellent in the center. But that's with the focus control all the
way up and the convergence control all the way down. The latter
converges the blue and green and leaves the red 3/16 inch off.
Moving the convergence control all the way up converges red and green
with blue off, and ruins the focus.
Any suggestions, other than dinking with the divider chain?
I did set the HV to 19.5 kV (with the CRT disconnected) and
measured the focus and convergence, and they were at least ballpark
OK (I had to use a scope due to the nature of my HV probe ... I
can make an adapter to use my Simpson meter, and will.
Its got an odd resistance ... 2.165 Gohm which corresponds to
13.6 uA, so my multimeters aren't very accurate.
I think I need help with this problem.
And there's another one ... the adjustment magnets
on the purity assembly don't do anything ... at least moving the
little knurled knobs doesn't do anything. And one is missing.
I might have misunderstood how these work ... I was screwing the
knobs ... are you supposed to screw the threaded rods and then
tighten the knobs to hold them? What to do about the
missing one?
|