Two more questions! When the picture goes absolutely totally blurry on an
all-white screen, is it the 19,500 volt HV or the focus voltage, or both,
that collapses? I suppose I could measure them, but with the chassis
in the set and turned on, I'm afraid of accidents.

I'm missing my horizontal and vertical hold knobs. The rest look
rather generic ... where do I get matching ones?

No knobs, these are just knurled shafts.

jr

"Are all of these CT-100s actually supposed to get UHF, or only
some of them? "

Do you have the proper strips installed for the channel?

jr

Doug will be getting a UHF strip from my collection. We have been in touch. And I have more if anyone needs one. Stay tuned.

REALLY? I find that hard to believe! These are user controls.

McVoy did, however, say "all knobs"

I am about 99% sure that the horiz and vertical shafts were never fitted with knobs. If anybody here can prove otherwise, that would be welcomed information! The CTC-4 also has a similar concentric knurled shaft configuration in the pencil box, but in that case it is for vertical and tone controls.

jr

My CT-100 has just the knurled shafts, and this diagram seems to show them without knobs.

http://antiqueradio.org/art/RCACT-100Controls.jpg

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Well, Steve then must have been right ... it was all there.

I'm watching the Bear's game on the CT100.
From 4 feet away.

Other than the screen size, I don't see the complaints
people made in 1954. There is simply
nothing wrong with the picture, even brightness.

Is it that Videokarmites are more picky about adjustments?

The CT-100 can make an awfully nice picture. It's also complex and it requires careful setup. I wasn't watching color TV in 1954, but I wonder if many of those complaints were due to plain old misadjustment -- either because Grandpa started fiddling with controls or because the TV was never set up perfectly in the first place.

It looks like your CT-100 is dialed in very nicely, in any case. Impressive.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

As bad as it sounds, I wonder if early complaints about color TV were just a variation of "flashing 12:00 syndrome"-people having one too many adjustments to handle and then losing everything as a result?

There's a story of when Zenith engineers were shown the chassis, one of them commenting "Twenty-seven controls, each one making it worse!"

The set was working great on program material and most
test signals from the Digital Video Essentials DVD, and my own
test patterns, but not the horizontal and vertical color bars and
the red and magenta full 100% screens from the DVE DVD.

The bars showed incorrect luma for different bars and color changes
vertically across the horizontal bars.

This was traced after a VERY long session with a scope (and
the chassis in the set) looking at test points at the grids
of the first video amp, I and Q demodulators (removed from sockets),
and the three CRT grids.

The luma problem was a very slight misalignment of
the RF which I had simply not done (fixed), and the other is
(not fixed) a great sensitivity to the horizontal hold
when there is a saturated color right at the start of
a lot of horiziontal lines. Its got to be just right
so the burst sync timing is just right. This does not usually matter.
The waveform when I was aligning the burst stripper looked OK but not great.
I will have to study the circuit a lot before removing the chassis, which I will
have to do anyway to insert a UHF strip.

I was worried about signal overload, but tests show the set works
OK over a 66dB range from extreme noise and barely syncing up to
the normal power of my Blonder-Tongue modulator (which is set well below
max). At high powers one sees a few percent of nonlinearities, not
visible on pictures.

"27 adjustments and every one makes it worse". That's
a quote I read in an earlier thread, attributed to a Zenith guy.

Was it a complaint or a compliment? Did he mean 27 was too many
or that somebody had all of them perfect so that any change made it worse?

I see what he means though ... 27 is a lot. But I count exactly 69,
counting only one channel in the tuner. I adjusted the last one today,
the I-Q phase difference for the two synchronous detectors. This
make the red and green waveforms perfect and the blue within
a 10% resistor tolerance. Yellow is now yellow.

I'm theoretically done! The only thing left is to get Ch. 39 working
and replace a temporary resistor mess in the power supply.

Oh! 69 is only the chassis. If you count all the tilts and pushes and
magnets on the CRT neck its 80. Add CRT rotation itself and its 81.

81 adjustments! You are making me think I should charge more, if I ever make a business out of restoring early color TV sets. :)

Charge by the hour!

Of course, the vast majority, once done, will last a long time.
If the remaining white peaking coils go, I don't think new ones
will change alignment.

Not to mention that this was a great learning experience for me ...
I'd never done a color TV setup since the late 60s,
and those were Heathkits. Doing it again would be faster, but not
easier. For a restoration you don't know whether a problem is a bad
part or adjustment until it is completely fixed, and there are
wrong leads ... like the modulator adjustment below. But the symptoms
it caused were also in part caused by wrong IF and RF alignment.
Two different problems, each of which required the same two different
fixes.

I found another adjustment that needed fixing for "blown whites",
wrong gamma of luma as color came near saturation,
and what looked like poor DC restoration, but
it was not on the TV, it was the video level
on my Blonder-Tongue BAVM modulators. If
set for auto level, which seems to work perfectly on
my Sony LCD monster, and is extremely subtle but there
on my 40's B&W sets, it was causing these problems.

I now have two channels to watch on NTSC: Ch. 6 for
OTA digital, and Ch. 10 for DVD. Hopefully tomorrow I
will have OTA Ch. 39 (HSN) for a few more months.

Thanks to Dave A for the UHF tuner strip.

I was particularly impressed by the free shipping and the
return address on the box.

The strip had the worst case of sulfide attack I have ever seen.
Everything copper, silver, or brass was covered with a thick black fuzz.
This responded to no chemical attack alone so I used a half a box of
Q tips and Brasso, followed by lots of alcohol,
more Q tips, and then De-oxit.

The strip comes as Ch. 34 but changing to 39 is very easy:
tune the oscillator with a spectrum analyzer, tune in the station,
and tweek the RF adjustments for a good picture.

I'm now now looking at some woman with horrible splotches
of something white on her face ... this is a shopping channel.
But its real, analog NTSC, OTA TV. I think she is in need
of a sunburn remedy. That's probably what it is ... I have the sound off.

Doug, thanks for a tip of the rabbit ears for my contribution. The sulfide is not surprising given 60 years in a sealed box. Awaiting pix of the OTA. More parts are available from my donor chassis if needed. But not the fly...saving for my CT100. PM me.

Here are the true OTA pictures of Channel 39. This is a 12.5 kW station
2.75 miles from me .. through my walls, with
a double bowtie antenna. The good picture is with a 16 dB
amplifier with a 0.5 dB nf and the noisy one is direct.

Nice! - but I hope you didn't buy that poncho <grin>

I don't know if I missed it somewhere earlier, but could you give more information on the particular amplifier you are using? Brand, model, where to buy, sensitive to overload, pros & cons, etc.

Thanks.

.

Its from Advance Receiver Research http://www.advancedreceiver.com/

It has to be a custom model. Its similar to P470VDG or P902VDG.
You just order a different center frequency. Price is $90 to $130.

Specs (at about ch 39)
NF 0.6 dB
Gain 18 dB
1 dB Comp dBm +12
1 dB BW 30 MHz
Type: GaAsFET
Power: 10-16 VDC

Mine's ordered for Ch. 44 so depending on how
it was tuned it is likely a little bit down in gain at Ch. 39.

For indoor use there are no cons except need for a wallwart. Outdoors,
it needs weather protection and power sent to it.

Doug

Thanks, Doug. I'll have to study those to see if they'll help me here.

.

I should add it it really is better than the regular
ordinary broadband ones, even good ones. Ch. 44 is 68 miles from me over a hill, and without that preamp, its over the digital cliff. With it, 99.95%
reliable. (That's not with the bowtie ... it with a 20 element
single channel YAgi).

Original circuit be damned ... I've ordered 20 200v Zeners for the focus.
So far, I have not changed the circuit functionality, as
I don't consider replacing a selenium with a silicon and series resistor
changed functionality. It really needs regulated focus.

I installed 2800 volts worth of Zener regulating the focus this evening.
As an earlier restorer said, it works. Focus is perfect from
black to bloom.

I'm curious - does it maintain focus if you vary the line voltage (so other things are varying while focus voltage is constant)?

I didn't test. I will. I suspect it will, since the 19.5 kV is also
regulated and the convergence electrode runs off that. The small difference in screen voltages likely won't make any difference. My Variac can take the rather
large power need.

I tested focus versus line voltage.

Yes, focus varies. +-5 volts is "OK" but needs adjustment.
+-10 volts is not OK and the height changes wildly
as the line voltage is changed. However color and overall
picture quality stay good.

If you have problems with AC mains voltage fluctuations then I would recommend looking in to obtaining a saturable reactor 120V isolation transformer. Those supply regulated 120V AC output as long as the input voltage is between ~85-155V.

I used to have one of those transformers which I used on
my photo enlarger lamps. It weighed like 30 pounds but still
probably didn't have the power for a CT-100.

However, where I live the voltage is rock solid at about 120,
and I set the adjustable the B+ resistors for that voltage.

One more niggling problem: horizontal ringing.

That is, ringing in the horizontal sweep waveform. I see it
in a scope waveform with a probe dangling near the yoke.
It looks to be about 175 kHz. This is very clear.

I see it as waviness in a diagonal line pattern across the screen,
barely visible. I see it as bright bars in a black background, barely
visible. I see it as scrunching up or spreading out in the bars
as a scene pans across the screen. This actually is clearer
than on the diagonal bars.

I've tried finding this problem in the archives here and
find two suggestions: replace the damper tube and the
270 pF capacitor in the yoke. I have no mica caps in a high enough
voltage ... would two 130 pF 6 kV ceramics in parallel do? I
don't know if our stock has the 6AU4GT.

Question: are there other things to check, especially ones
I can just "test" to see if they are good?

I looked at the 270 pF capacitor in the yoke .... its the
biggest dogbone ceramic capacitor I have ever seen!

I replaced the damper and it fixed the problem say 90%, which is
plenty good enough.

It turns out that the "shunt" pot in the tube tester was dirty
and it was giving wrong results for diodes.

That was premature. It did help, but not 90%. I tried replacing the cap in the
yoke, That did make a change, but its not 100% fixed. It reduced the length
of the ringing but made the first ring a little worse.

Any more suggestions?

I'm posting a few more pictures. These are pairs of original
.jpg photos and screen shots of the CT-100 displaying those
pictures through a USB key played on my Sony Bluray player.
They were adjusted in Photoshop so that
they look as similar as possible (i.e. very similar indeed), seen
on my computer monitor, to the CT-100 on which it was sitting.
This means its a very very fair comparison to the originals, compared on
your monitor.

comments:
1) the purple flower picture looks the same, colorwise, on my calibrated
LCD 55 inch Sony as it does on the CT-100, i.e. wrong for
some reason.

2) some of the pictures show a split image, split along a
horizontal line because the 1/8 second exposure was not in sync with
the TV scan. One part is yellower than the other. The yellow part is
wrong compared to what my eye saw, the non-yellow
part is correct.

Edit: oh yes ... the flowers are spring in Urbana IL, the other two are
in downtown Kuching, Sarawak, Borneo, Malaysia.

Beautiful!

Its been a while but last week I got a bee in my bonnet to try to fix the
last color problem in my CT-100.

This was caused by a mention of old color bar generators in another forum here.
I realized that I could make one using a computer program to generate an
image, screen grabbing it, and putting in a file with Photoshop. I did so
both with the "real" ones that RCA generators made back in the day, and
a different one that showed the whole 360 degrees of color. I also made
one of each with black bars and one where the Y was constant over the whole
image.

This meant that I could now do the "main official" color adjustments rather than
the "second best" ones they describe using essentially what became SMPTE bars.

It turned out that the angle I had set for the phase difference between I and Q was
90 degrees, exactly! I set the Q phase as described, and the I looked perfect.

Then I tried setting the I gain using their procedure which involves looking at the R, G, and B grid signals. It would not go high enough
for the scope traces to look perfect. So I tried increasing the Y gain by putting
a 2700 uF cap across the I demodulator cathode resistor. This allowed getting the
three signals ALMOST right .... but red and blue looked clipped! Turning down
color gain ALMOST fixed this. But ... the bars LOOKED worse!!! Too much blue on the right center part of the screen. And still, the top of one sine curve clearly
was clipped. So I removed the cap. Still a bit clipped! Turning down either
contrast or color gain or I gain didn't help.

Turning down video gain on the modulator did get rid of the clipping. Then I checked
the I and Q waveforms for correct 90 degrees ... still correct. Adjusting I gain by eye resulted in a much better color rendition. It was about 80% of full scale, rather than
100% as before. The RGB waveforms were good but not perfectly as in the manual,
but no sign of clipping.

Then I looked at SMPTE bars .... as good as I had them before, but good, still
not perfect, but slightly differently not perfect.

Then I look at my standard test pictures, including Dorothy first seeing the Scarecrow, some flowers (the ones I posted) and, and, most important,
a bunch of Christmas cards I got off the net that had balls the exact color violet
that was not reproducing well before. Better. Maybe the
blue gain and screen were not set quite right ... too high a color temp.
Changing that a tiny bit helped the color too. FINALLY!

Then, GO CUBS!, I watched the Cubbies beat the Sox by one run, and the colors
matched my Sony HDTV even better than before, especially yellow and yellow-green,
which had never been really right. Note that the real RCA bars don't show yellow and yellow-green while my 360 degrees ones do.

Morals: don't overmodulate, and use the old style color bars that have the color phase
rotating 360 degrees over the whole horizontal cycle.

Also, the color bars with the constant Y background make a good test for old B&W sets as well as color ones: there should be no brightness difference across the whole
screen. My CT-100 was good before, now its near perfect. The TRK-12 really has
absolutely no luma variation, though up close you can see the color signal if
you move your eyes at the same rate the diagonal bars move.

Bravo! Good show!