[b]8 Days Until the 2022 Early Television Convention. Register Now.[/b]

[Steve McVoy]

8 Days Until the 2022 Early Television Convention. Register Now.

If you are planning to attend, please register before Monday, May 2 for the convention. We need to let our caterer know how many attendees we will have.

May 6, 7 and 8, at the Museum in Hilliard, Ohio.

The Convention will include a swapmeet, auction, lunch, presentations, dinner, and demonstrations of the sets in the museum's collection, plus time to meet with other collectors.

There will also be a sweepstakes this year, with the drawing taking place at the Convention. The Grand Prize will be an extremely rare RCA TRK-120.

Here is the schedule. You can register for the convention here.

https://earlytelevision.org/2022_convention.html

[zenithfan1]

I registered, but now unable to attend.

[Electronic M]

Originally Posted by zenithfan1

I registered, but now unable to attend.

Ouch!

I had the opposite problem. I could attend but I couldn't register...I've got NoScript running on my browser and the form didn't load but it's page did so it looked like the site was incomplete, and it took this thread being posted for me to give it a second hard look figure that out/get registered.

[dtvmcdonald]

The meeting is now over and was a general success. The two talks were unusual but excellent.

The "repair" days on Thursday and Friday did not go as well as one could have hoped.
I worked on the CTC-5 Deluxe which started with a nice blank raster with bad
gray tracking.

Fiddling with the connection to the house RF distribution resulted in a terrible picture.
The fine tuning did not work. This was traced to a bad clutch, which a bit of "working with"
got going "well enough". I set up my own signal setup (Blu-ray player and B-T agile
modulator) which resulted signal which varied with channel. I settled on Ch. 5.
But I forgot the remote so had a limited of patterns (which did include crosshatch.)
(I use patterns of my own divising, .jpegs on a USB stick.) I tweeked the convergence
just a bit. The AGC did not work so I had to use an attenuator. Overnight I visited Walmart
and got a universal remote that allowed access of color patters, clumsily.

The gray tracking was fixed in two minutes into "excellent".

Thursday I attacked color. This set is unique, using R-Y and Q demods. The Q was dead. A lot
of time was spent doing resistance checks using tube extenders, and swapping tubes in the
color section. All the tubes were functioning somewhat but the
resistances were high. I brought in the scope and determined that there was both signal
and 3.58 drive to boith demods and that the matrix at least a bit functional Hours were
lost because I was using the wrong AGC control!
Once I found the right one the AGC started at least a little bit.

The color was all in the R-Y channel --- no Q thus no green or magenta.
Finally I broke down and with several actual "Experts" standing by got out the magic
diddle-stick and tweeked the color demod angle looking at the screen. This resulted in
all colors at least a little. We ran of of time. Picture is horrible but colorful. I
think that at least two full days of alignment is needed after a careful resistance
check and re-resistor session. Probably three days total on the bench.

This set will not get better without a complete total alignment. The B&W bicture is
rather ringy on all channels, especially 3.

It was found that the RF feed was bad ... including some sort of interference.
It was changed to a good one.

Other sets being worked on fared worse. The CT-100 never got color. The Royal Soverign
was never made watchable. There was (as far as I know) nothing wrong
with the Philco Predicta and the repaired feed gave a very nice picture. The two main CBS
color sets were generating their usual gorgeous pictures of Dorothy.

Only one prewar US set was working, a non-RCA TRK-12, giving a mildly dim but OK picture.
One prewar British set was working, a Murphy, but it was misadjusted so badly that only
a "random twister" could have done it. After quite a while trying to figure which knob
did what I got a watchable but dim picture.

Somebody earlier had adjusted the WWII military iconoscope camera and it was producing
a really excellent picture for the low light level it gets. It had a really squared up
raster and a perfectly round test circle.

[Penthode]

Curious. What did you do to get excellent B&W tracking? My CTC5 is reasonable except at higher brightness. I attributed CTC5 problem just to an old 21AXP22A.

[dtvmcdonald]

Originally Posted by Penthode

Curious. What did you do to get excellent B&W tracking? My CTC5 is reasonable except at higher brightness. I attributed CTC5 problem just to an old 21AXP22A.

I adjusted the red screen control. That's all it needed. The CRT is good enough that the red remains OK all the way to blooming. I set the contrast a bit below that. At one point on my own color bar pattern which has
not only blue bar matching but red and green bar matching I got all three
almost perfect, but at that point the color frequency response was extremely bad. The alignment must be horrible.

I've never found an old tube set with anything but terrible alignment
except my TRK12 which came to me untouched since worked on by
RCA research in Camden, around 1946. Its alignment was identical to a perfectly aligned CT-100. My Pilot 3 incher and one Hallicrafters
electrostatic set were actually oscillating!

Doug

[old_tv_nut]

Not sure what R, G, and B bar matching has to do with color frequency response (or vice versa).

I would expect simultaneous R, G, and B bar matching to depend mainly on demodulator angles. You can always adjust hue(tint) and color level to get one of the three to match.

[dtvmcdonald]

Originally Posted by old_tv_nut

Not sure what R, G, and B bar matching has to do with color frequency response (or vice versa).

I would expect simultaneous R, G, and B bar matching to depend mainly on demodulator angles. You can always adjust hue(tint) and color level to get one of the three to match.

Color matching: I didn't intend to say or imply color frequency response.
I meant IF response, which can cause overload problems unless AGC is defeated.

Your second comment: it depends on demodulator angles and at least one matrix intensity adjustment plus hue and saturation.

[old_tv_nut]

Originally Posted by dtvmcdonald

Color matching: I didn't intend to say or imply color frequency response.
I meant IF response, which can cause overload problems unless AGC is defeated.

Your second comment: it depends on demodulator angles and at least one matrix intensity adjustment plus hue and saturation.

Much clearer - thanks.

[dtvmcdonald]

Let me expand on my explanation: when the color was correct, the RF fine tuning was tuned, as best I can tell, so that the color carrier was tuned
in the IF strip where the audio carrier is supposed to be! The audio was well
down in frequency (in the IF of course, as the RF signal is lower in frequency
than the RF oscillator) to where the IF response was nil, so no audio bars.

This meant that the main video carrier (in the IF) was well down in frequency into what should be the flat part of the IF response: 6dB higher in amplitude than its "proper" spot half way up (in amplitude) on the IF response.

All this implies to me that something awful is wrong with the RF/IF response curves. The fact that the problem varies with channel when connected to my modulator with short cables (two, as there was a step attenuator there) implies its in the receiver. Ch. 3 was particularly bad. I checked that it was not the external balun by using a resistive brigded-T pad in place of it.

[old_tv_nut]

Yep, definitely sounds like a full RF/IF trouble-shoot and then alignment from ground zero.

Was your RF source double sideband? Possible that the alignment/fine tuning was off enough that the set was tuning the lower sideband?

[dtvmcdonald]

No, it was a proper NTSC signal. It was a Blonder-Tongue top end cable
agile modulator with SAW filter.

The feed video feed to it probably is wideband. The waveform of a baseband
Q signal with bars at 1 MHz (2.58 and 4.58 MHz) looks like DSB suppressed carrier.