I got my CT-100 from the ETF home safely. Thanks to Steve
for getting it all safely in the van.

It appears mostly unmolested. I have tested all the tubes.
A few were missing. One had a bad filament. Four tested weak,
including the focus rectifier and the shunt HV regulator,
but I have my doubts as to how well the Hickok transconductance
checker did on them.

The bottom of the chassis in very nice clean shape. The top has been
partially cleaned and the rest is not bad. The HV cage is incredibly
dirty. It took a huge quantity of alcohol to clean the tubes in it.
What do people do to the parts inside? They clearly MUST be cleaned,
but should I take it all apart or try to clean them in place.
What cleaning agent do people use? Alcohol works, and
won't hurt the ceramic caps, but what about resistors, especially the
spiral high-ohmage ones?

About half the white peaking coils are clearly bad, half appear
to least to have the right resistance.

More, including pictures, later.

Some questions.

After careful examination, restuffing the chassis mounted electrolytic cans will
be a nightmare if done as described in the article mentioned in the sticky
thread at the top of this forum (remove can from chassis, uncrimp buttom) because
they are all soldered in, most at two or three places. Some are riveted in.

I'm not intending to leave the chassis bottom original looking, but I am the top,
more or less. I could do a "cut off at the base and cover the gap with
silver color tape" bit on them, but that would not look original even at a glance.

What I'm thinking of doing is just leaving them in as is, removing them
electrically, and adding terminal strips to hold the small new caps.
For the ones in the power supply, I would remove the seleniums, which are
huge, and mount the new caps, 1N4007s, and their associated dropping
resistors, on a circuit board mounted inside their cage. The rest should
easily fit under the chassis. What do people think of this ... it would be
easily cosmetically reversible if a future owner wanted to, as I'm saving all the
old parts.

Where is the Candohm resistor on the schematic?

:thmbsp: I say this with all due respect and no malice whatsoever ;

Some sets , sure , I'd go the terminal strip route in a heartbeat rather than dive into the mess of wires required to do a "pretty" restuff . But a CT-100 , THE holy grail of tube color TV to most collectors , deserves , no , , really outright demands ! , that a proper cosmetic restoration accompanies the electronic restoration . In my view , historical value dictates the extremes one should go to in preserving the original looks , and what color TV would be more deserving of proper cosmetic restoration than your history making CT-100 ?

Your set will only be virgin once ........

normally I don't worry about making it look completely original, I do cut off the cans and mount the alum tape back on , but that is for the sake of keeping lead dress the same. I never use term strips, just cut drill insert and solder. Sometimes I do not even bother with putting the cans back over the caps. Its just a TV and my only goal is to get it functional.

IF I had a CT-100 (which I prob would avoid since I would constantly worry about the CRT) I am sure I would go the extra mile to restuff by uncrimping and would also prob restuff the wax caps as well. It goes against my nature but due to the historical value of the set I think it deserves it. I think for me I would just look at it like this, its a one time deal, so take what ever amount of time is needed to do it right. Once its done its unlikely that that I would ever do again.

Here are some pictures.

Edit: I should add that the original of the chassis bottom is about
10,000 x 10,000 pixels, as mentioned below.

And here are more.

My goals may be different from some. Here they are,
in order of higher to lower importance:

1) Make the set work as originally intended, receiving signals
at RF with full exact NTSC specs: including correct Q signal
with 0.5 MHz double sideband and I with 0.5 and lower with 1.5
MHz bandwidth, even if
I have to create these myself from RGB output of a DVD player.

2) Leave the top view of the chassis unchanged as far as
possible. If there are bad controls I will try to find proper looking ones.
There is a white peaking coil there, which I will replace,
and a paper cap. The cap will be restuffed and I will make a little
paper cap to cover the new coil, not perfect but will do.

3)Save all removed or replaced parts. I have made a 100 megapixel
image of the chassis bottom so that a future owner could
do a full restuff with proper placement. I'm not going to restuff
anything under the chassis.

4) Leave the horribly dirty areas as clean as reasonable. This
is not a 60's Tektronix scope, where the factory manual
says to start a calibration with a good hosing down and sun dry!
Water or even gallons of alcohol would damage coils. The cleaning
has to be done with paper towels and Q-tips. Wires on the
chassis top and insides the cages are filthy and slimy. Goop followed
by alcohol seems to be the cure.

That said, I have decided to not restuff the can electrolytics ..
doing it without damage while unsoldering them from
the chassis would be a nightmare and possibly beyond my skill.

I'm going to compromise on point 1 above and remove the seleniums
and install silicon diodes, their series resistors, and the new
electrolytic caps for the power supply in the cage
mounted on a fiberglass perf board. The board and caps
will be painted bright orange. That will have to do for "the look"
inside the cage.

Doug McDonald

Hey those orange things with the fins are pretty neat looking.....

You gunna keep them the original color.....?

Hey those orange things with the fins are pretty neat looking.....

You gunna keep them the original color.....?

As I said, they are going into the "removed innards bag" that
some day sells along with the TV. They will be replaced with
modern parts, completely different looking, painted that color.
If you are unfamiliar with these sets, they are inside the perforated
metal cage at left in the chassis top photo, and are essentially invisible
if you look inside the set with the back removed. The top lifts off this
set and they are visible, inside the cage, with the top off.

Oh! I have another idea: series dropping power resistors have to be added
in series with silicon rectifiers. I could use resistors intended to be
mounted on heat sinks, and paint the heat sinks that color.
The originals are 3 inches square. These could be as
wide but only 3/4 inch or so high, leaving room for the caps I will put there.
I'm feeling much better now about the original look!

Ideas like that last one are why I am seriously over-planning this project.

I have completed cleaning and recapping the HV cage.
This was a nightmare because it was so dirty and cramped.
The 2.7 Meg 1/4 watt resistor was at 3.3Meg, and was
replaced with an identical but in-spec part.
The two 25 meg
HV ones were right on the button.

"After" photos are attached.

Looks like a good start. There's no such thing as too clean, when it comes to the HV cage.

Take your time and enjoy. My theory with a project like this is that I may never get another chance to do another one of these. It's not a race, I sometimes have to remind myself. It's better to do a job right the first time than to beat some imaginary clock. And while the rest of us may offer advice or cheer from the sidelines, you are the ultimate arbiter of what is "the right way."

Regards,

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

Looks like a good start. There's no such thing as too clean, when it comes to the HV cage.

Take your time and enjoy. My theory with a project like this is that I may never get another chance to do another one of these. It's not a race, I sometimes have to remind myself. It's better to do a job right the first time than to beat some imaginary clock. And while the rest of us may offer advice or cheer from the sidelines, you are the ultimate arbiter of what is "the right way."

Phil Nelson


I agree. I'm working on it about an hour or at most two a day.
More and I get eyestrain and overexcited.

This morning I went though the Sam's resistance to ground
chart. The vast majority of the numbers are well within tolerance,
most well within 10%, including most > 1Meg resistors.

This is good news.

This evening I will do the resistance to B+ part.

I noticed that Sam's has a 12AT7 on their topside tube chart in
a 7 pin socket! (Its really a 6AU6).

I still have not got a reply to where the Candohm is in the circuit,
and the nature of the 100 ohm resistors inside the chassis connected
directly across its parts. Are these R286 and R287 in Sam's?
The ".100" resistor in Sam's surely must be 100 ohms, otherwise there
would be nowhere near -30v on the bias supply, as there can't
possibly be 1.7A B+ current.

Looking Good!


I still have not got a reply to where the Candohm is in the circuit,
and the nature of the 100 ohm resistors inside the chassis connected
directly across its parts. Are these R286 and R287 in Sam's?


I believe that the Candohm on the back of the chassis is R-285 (see arrow on page 20 of Sams), a 33 ohm resistor shown in the power supply. it is in parallel with a 100 ohm resistor, R-286.
The two U-shaped loops that you pictured earlier are "fuses" M-6 and M-7 in the heater supply... they are just short lengths of #26 wire enclosed in sheathing.

jr

OOPS! double post!

jr

"All" I did today was disconnect the vertical convergence transformer from the
focus pot and its 0.01 uF cap and apply an external 5.2 kV through a 750 Meg resistor and a microammerter in series, for an hour (at room temp of course) to test
the transformer "safely". (Safely for the transformer with the 750 Megs and
safely for me with everything except the 5kV supply sitting on my 1/2 inch glass
dining table.)

It passed. Of course this is not forever at higher temps, but its better than fail.

Doug McDonald

Yesterday I recapped the underside of the HV and HOT area and the
vertical convergence amp.

The latter was a disaster zone.
All resistors were way off value except a 270K in the first stage plate.
And that one appears to be the wrong value, despite being listed as 270K
on the RCA schematics! The tube has 9.3 volts listed on the cathode
with a 2.7K cathode resistor. That's 930 volts across 270K ... not right.
Sam's has 27K there. It looks like I need to change it to 27K.

And the cathode resistor in the second stage was 47 ohms ... both RCA and Sam's
have 4.7K with 20V and a 100 uF cap across it ... very reasonable.

Thus, this set much have been seriously worked on in the past. I'm going to
have to check each part value with both RCA and Sam's, a nightmare. There
are resistors and caps everywhere that have been replaced with 1950's parts
by cutting leads and twisting the new leads around them.

Oh did I mention that one lead of a cap in the vertical convergence amp
area was already broken, and when I touched the cap, the lug on the tube socket
attached to it fell off? I was able to kludge that by soldering a #32 wire
to the remaining tube pin part since it is a 7 min miniature socket.

But the bottom does LOOK perfectly neat. The previous owner (who was
a TV person and probably did it himself) did a good looking job.

The 1954 RCA book "Practical Color Television For the Service Industry" shows a 27K resistor to pin 6 of the 12AU7 (Vertical convergence amp) and a 4.7 K from pin 2 to ground.
jr

Thanks for the pointer. In other words, RCA corrected itself.

I'm half way through the three color amps. Good resistors,
but there was a replacement coupling cap that had one end NOT SOLDERED,
just LOOSELY wrapped. Could this set have worked? At all?

Thanks for the pointer. In other words, RCA corrected itself.

I'm half way through the three color amps. Good resistors,
but there was a replacement coupling cap that had one end NOT SOLDERED,
just LOOSELY wrapped. Could this set have worked? At all?

Clearly not a Heathkit version, which would have had a checkbox for the soldering step! :D

I'm now about 60% through the recap. With the chassis vertical,
power transformer at lower left, the left half and the bottom 1/4 is done
except the 4 big power supply caps.

Interesting tidbit: there are many 0.1 uF "paper" caps in what looks like
ceramic tubes. I'm replacing everything, and the replacement
Panasonic mylar ones (listed 5%) are typically within 1% ...
but so are most of the ceramic case ones removed, and they all
would be in tolerance at 5%. Could these be early plastic caps? Removed waxed paper tube caps are all over the place in value.

I found another cathode resistor that was low (by a factor of ten),
i.e. it is marked that, and measures it too,
and the voltage listings again say (and so does a reasonable current)
that the schematic value must be right. This one clearly is original ...
from RCA! Bizarre. Were the assembly line workers color blind?
(That's actually meaningless in this case, since it was black band
versus brown, unlike black versus red in the previous case).

Was it traditional to use 50-50 solder in those days? I have older
radios and TVs that had 60-40 (tin-lead) solder. And the solder
is in very very big blobs, much bigger than necessary. There's
probably a pound of excess solder (maybe a slight exaggeration.)

The white ceramic tubes with values that were also available in cardboard cased paper were typically also paper caps, but with a fancier shell. They usually test bad at working voltage even in sets a decade+ newer. Don't hesitate to replace them.

The recap of the paper and tubular electrolytic caps is done. I still have the chassis
mount caps in the power supply and at the front of the set opposite the tuner to do.
I'm going to do the latter set today, then I have to make mounts for the
power supply ones. I'm not restuffing them.

After seeing the chassis bottom after the recap, I'm quite happy with its
look. Its not original, but it sure looks neater and not so cramped. I'm
not happy with the look of the blue rectangular caps I had to buy for some values,
like 0.001 or 0.0022 at 1600 or 2000 volts.

I'm going to look for better looking ones, either Panasonic brown or
axial lead. I assume that mica or polypropylene would work. Is that correct?
The blue ones I have are rated for RF current use, which their spots are used for
(well, overtones of the sweep frequency.) Any suggestions?

Sunday (the 27th) I completed the recap except for the B+ supply.
Monday I designed and built a B+ supply replacement
for the SE diodes and the four big chassis filter caps.
A picture is attached. One of the four replacement caps
is visible, the other three are behind it and not clearly
visible.

After finishing, I inspected the chassis for about 20 minutes
for shorts and solder blobs. At this point there were no tubes or yoke.
I connected it to a Variac and slowly raised to B+ to 50 V [sic]
with no problems and let it sit for 30 minutes. The voltage
was monitored on a scope. Then I slowly
raised the voltage and at 140 I heard a "pop"
from the horizontal sync section. I turned off the power and
spent another 30 minutes inspecting, finding one solder
blob and one pair of tube pin connections that looked
a little too close, and fixed them. After that the B+ went to
240 with no problem. I didn't want to go too high with no load
since the nominal +385 and +285 were actually the same.
I then connected the yoke and purity coil and tried again, with no
problems at 220 v B+.

I then put in all the tubes but removed the ballast. Turning
it on produced filaments and no problems.

I reinserted the ballast. At this point I had a scope on the
400v B+. I set the Variac to 105 volts with it off and threw
the switch (did I mention the one on the set is broken,
stuck on.) Nothing awful happened: the voltage went up to about 370
and then down a bit. I checked the other B+ supply
voltages (385, the two 285s, the 200, and the -30). All were
as expected a bit low. Turning the Variac to 117 produced
reasonable values. Focus voltage was very roughly 8 kV and
HV was somewhat low at 15 kV. I turned off all lights in the room to look
for red plates and saw none, including the HV rectifiers and regulator
tube. Also, no bad smells.

At this point I hooked up my Ch. 10 transmitter and installed
the channel selector knob. It was not on 10. At this point
a minor disaster struck ... turning the channel selector knob
produced no clicks. Turning hard I got it to 10 ... just as the knob
broke. The crack is probably fixable.


I tried looking at the signal with a scope to the green signal to the CRT
and saw only hum. I then tried looking at the grid of the audio
output with the scope (the speaker is not connected). All I
saw was horizontal sync pulses.

At this point I decided to try a sweep generator. I connected the
scope to the test point at the video amplifier grid. Turning to Ch. 10
produced a passable result. So the tuner did change to Ch. 10.
I reattached the RF signal (of Letterman) and was rewarded with ....
AUDIO??? Yes, audio. It was clearly Letterman,
since the waveform followed the sound from my flat screen.
Perhaps bad fine tuning?
I installed the fine tuning knob and was rewarded by a
good video waveform. This is of course a big milestone!

At this point I checked for sweep from the yoke (clearly there
was horizontal there, since the scope probe picked it up.)

To do this I set the scope for X-Y with no sweep or signal , just
a dot in the center. I set the yoke on the scope
(which had the screen facing upwards)
with the set off and turned the set on. Soon I was
rewarded with a raster about 5/8 (H) x 3/16 (V) inch. Another
good milestone.

Finally I looked for sync. I put the scope on dual trace,
Ch. 1 to the test point, ch. 2 to a scope probe connected
to nothing (picking up horizontal sweep). Scope sync was to Ch, 1;
I could not get the TV to sync to the signal. I measured the sync pulse timing:
as expected 6.4 divisions. I switched sync to Ch. 2 and
measured the period: 6.0 to 6.2 division was the whole
range of the horizontal sync control: no wonder it did not sync.
A repair will be needed.

Then I moved the Ch. 2 to a test lead wrapped around the
vertical sweep tube and repeated the above, but synced to
the power line. The vertical was easily adjusted to be in sync,
though the range was narrow. A scope trace is attached.

That's enough for yesterday (its now 1 AM).

Doug McDonald

The horizontal was not broken, the oscillator transformer just
needed adjustment.

The video was getting all the way to the (unconnected)
CRT, but there was no color. This turned out to be
another invisible broken wire, in the reactance tube circuit.
Next is trying to get the tuner to tune.

Nice progress reports. It is good to know that you have had no major problems so far.

Nice progress reports. It is good to know that you have had no major problems so far.

I'm moving this to the color TV forum ... IT LIVES!

Its back here, for a few more technical notes.

While it worked, it became obvious that the CRT cathodes were
at too-high a voltage, requiring too much drive (contrast). This was
eventually traced to the 1.8K resistor in the CRT divider chain, which
was 18K when cold, lower when warm. I happen to have an
5W replacement part.

Also, the purity pot (20 ohms) in the B+ cage is bad. It probably
will work OK as its only broken near one end. I ordered a replacement
(25 ohm at 12.5 watts) from Mouser, but would like to find an
exact replacement. Where does one find such a thing?

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?

those are for Adjusting center convergence First, the screws themselves are magnetic and will sit very close to each pole piece of the Electron Guns, you adjust these First before other Convergence adjustments. the Nuts just keep them from moving after you adjust the Screws

Focus problem found: a previously good 8.2 meg 2 watt carbon
composition resistor which should have 2800 volts across it
(0.95 watt) measures 27 megohms.

Luckily I have a 10 Meg HV resistor I can use,
which likely will put the focus voltage in range. Also. its in
the HV cage which can be serviced without removing the
chassis from the cabinet.

The new resistor fixed the focus problem. I tried magentizing a
screw for a replacement purity magnet. It was not quite strong enough.
So I ground the top of the screw flat and superglued on
a small piece of a refrigerator magnet. This made it work OK.
Getting passable convergence was fairly easy.

I got around to playing with the B+adjustment resistors
I had installed. The B+ was at 355 and I got it up to 385,
which Sams says i Correct, so I left it there.

The only remaining problems are probably designed in ...
bright colors in large areas ruin the luma. Actually my Pilot TV-37
ha the exact same problem until I realigned it to not
overemphasize 3.58 MHz. The other problem
is serious blooming on white screens.

Pictures this evening when window reflections wont be
a problem. I'm not showing Dorothy ... my copy is pillerboxed.

Didn't take pictures last night. I decided that it still
was not right. Guess was that the drop in luma when full brightness
full saturation R appeared was caused by clipping in the detector
because the luma carrier was too far down on the 45 to 46.5
MHz slope, and the chroma was much much too high. I had looked
at the response crudely using a CH 10 rf sweep and it looked
like a sin curve from 46 to 41.25 MHz for the IF. I was unsure
of this since I didn't have a proper bias box.

Today I did an alignment. But there was a problem: the
cheapo Eico generator I got off Ebay leaked RF out the line cord.
That was fixed by removing the knot from the line cord,
shortening the leads to it, and installing new and better safety caps
as close as possible to the line in, the ground end soldered directly
to the chassis. The caps should be broadly series
resonant somewhere between 40 and 160 MHz. This worked.

Then I did the "Overall IF Alignment" on page 19 of the
RCA service manual. All the traps were already quite accurate so
I touched only 1T109, 1T110 and 1T111. This took a while with careful
notes of where I left everything since I wanted to be able to go back
if needed. 1T109 and 1T111 were within 160 degrees of
correct, but 1T110 had to go 1 1/3 turn clockwise. This resulted in
an almost perfect curve. The little bump
below 41.25 MHZ was a bit smaller than shown in Fig. 27.

I had earlier today generated true proper test patterns for an
IQ color set. I will make these available somewhere. They are
jpeg files generated in Photoshop by calculating Y, I, and Q levels
mathematically for various color patches.

The 2 main files have +I, -I, +Q, and -Q all at the same color level
and the luma calculated to make high saturation without going more than 5%
blacker than black or whiter than white. One file has full bandwidth
color (to 4MHz) in the jpeg, the other has I limited to 1.5 MHz and
Q to 0.5 MHz. (This was done by converting to Yab in Photoshop and
applying a "motion blur" to a and b only.) The -I to +Q transition was
filtered at 0.8 MHz.

I then copied the files to my Sony Blueray player and played them.

The result on the filtered IQ test are amazing. There are no off-color
fringes except a tiny one in -Q. The +-I transition is clearly three times
the resolution of the +-Q one. The unfiltered file shows
the expected 0.5 to 1.5 MHz crosstalk that so
mars cheapie color decoders (and encoders).

Its not as good as my 55 inch LCD TV on the same NTSC, but its close.

And the problem with saturated reds and yellows is gone.

Next is dinner.

Here are final result images. These are taken with a digital
camera and processed in Photoshop. I have not changed the color
but did brighten some. All were processed in Photoshop taking
care that no pixel was overloaded. The non-CRT dot images were
blurred correctly before resizing to avoid moire.

These are off-the air digital TV images.
The next post contains technical images.

The first one is the IF response. The marker is at the video carrier.

The rest are of the picture I made and played on my Blueray player
that contains images of R G B fully saturated but
different brightness on the top row, and +I -I +Q -Q on
the bottom row. The transitions on the top row were not
filtered in Photoshop (before playing the test file ... not the
camera images), while the bottom row was filtered to the
NTSC specs for the +_ I and Q transitions, and
filtered at about 0.8 MHZ for the -I to +Q one.

The final image is the histograms made from my
digital camera images of the flat (appropriately blurred)
parts of the patches. Its not perfect, and I also note that
I don't know what the gamma of the camera is ... this is
not photometric.

One more piece of data. I took the picture in the last post of the
+I > -I and +Q > -Q transitions, smoothed out the dots, and
converted from RGB to Lab. Lab is similar but not identical to YIQ.
I rotated the UV axes to actually be as close as possible to IQ.
I then made grayscale plots of "LIQ" for (top three) the I transition,
and three for the Q one. These are in fact highly contrast enhanced.

These do show some cross-interference between I and Q and
also show the fact that I has wider bandwidth, though the latter is better seen in the thumbnail of the color pictures.

Wow - great detailed work.

I have a question about your +/-I and especially +/-Q signals:

When you filtered the Q, did you delay the Y to match? and did you also delay the I (less) to match Q? The magenta/green Q transition appears to be later than the Y transition (the colorless area is on the right side of the brightness step). If you turn down the color to get monochrome, where does the Y transition appear compared to the Q transition?

Some amazing work there! I am quite impressed.

Wow - great detailed work.

I have a question about your +/-I and especially +/-Q signals:

When you filtered the Q, did you delay the Y to match? and did you also delay the I (less) to match Q? The magenta/green Q transition appears to be later than the Y transition (the colorless area is on the right side of the brightness step). If you turn down the color to get monochrome, where does the Y transition appear compared to the Q transition?

When I did the filtering, there was no delay. That is,
Photoshop left the center of the transition at the same "time"
for each channel. I don't
know if it is supposed to be done in the camera chain. What I
did would be correct IF the camera chain does the correction
AND the Blonder-Tongue modulator does not.

In any case, You can tell for yourself whats going on
by looking at the B&W images I
posted of the individual channels. Its visible in the original JPEG before being played. Attached. Note that the Y really IS unfiltered in
this file ... you can see that in Photoshop by converting to Lab.

Ah - I think I see the problem. You did the filtering for the source signal as some sort of Photoshop motion blur, correct? It is showing very sharp transitions into and out of the "blurred" area between the magenta and green. This is not normal filtering, and results in strange effects.

Here are some simulation results with proper filters in Photoshop. The simulation includes the modulation and demodulation, so cross-color (orange/cyan moire' in striped awning) and cross-luma (dots on vertical edges of the bars) are visible.

The smaller +/-I and +/-Q bars at upper left center have no Y variation, so you are seeing just the effects of I and Q there.

There is some anamorphic stretch due to adjustment to get the color subcarrier dots approximately correct coarseness.


Original:
https://farm4.staticflickr.com/3878/14840449302_a502a86c42_b.jpg (https://flic.kr/p/oBpbxy)veg market with IQ bars and cbars (https://flic.kr/p/oBpbxy) by old_tv_nut (https://www.flickr.com/people//), on Flickr

chroma on gray with transmitter I and Q filters:
https://farm4.staticflickr.com/3870/14840765275_20c599d3d8_b.jpg (https://flic.kr/p/oBqNtn)chroma in IQ filtered (https://flic.kr/p/oBqNtn) by old_tv_nut (https://www.flickr.com/people//), on Flickr

Demodulated chroma on gray with both transmitter and receiver I and Q filtering:
https://farm4.staticflickr.com/3889/14817794066_8029e51d1a_b.jpg (https://flic.kr/p/ozp4W3)chroma out IQ code + IQ decode (https://flic.kr/p/ozp4W3) by old_tv_nut (https://www.flickr.com/people//), on Flickr

Demodulated I:
https://farm4.staticflickr.com/3880/14654120389_1d13c4dab5_b.jpg (https://flic.kr/p/ojWcs6)I out as mono (https://flic.kr/p/ojWcs6) by old_tv_nut (https://www.flickr.com/people//), on Flickr

Demodulated Q:
https://farm6.staticflickr.com/5589/14840765735_0fcc9483c4_b.jpg (https://flic.kr/p/oBqNBi)Q out as mono (https://flic.kr/p/oBqNBi) by old_tv_nut (https://www.flickr.com/people//), on Flickr

Final output:
https://farm4.staticflickr.com/3853/14654120739_b8b56436b0_b.jpg (https://flic.kr/p/ojWcy8)final out IQ code + IQ decode (https://flic.kr/p/ojWcy8) by old_tv_nut (https://www.flickr.com/people//), on Flickr

Both the cross color and cross luma are more visible than normal because they are stationary.

Last night I tried to receive our actual OTA real NTSC Ch. 39 and
failed. I also failed to find a radiated local oscillator signal at UHF with a
spectrum analyzer, though I see it at VHF. I should add that the signal
is weak, but works OK on other sets because there is a 16 dB gain
0.5 dB NF preamp. Could this be a weak oscillator tube? It tests excellent.

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

Could bad blooming be due to use of a 1X2A rather than 1X2B? I forget
what I found in our old stock ... it tests good offscale.

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?

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.

No knobs, these are just knurled shafts.

jr

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

McVoy did, however, say "all knobs"

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>

The good picture is with a 16 dB
amplifier with a 0.5 dB nf and the noisy one is direct.
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.

.

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 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'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.

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


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!