Westinghouse K840CK15 Restoration

[etype2]

Happy Holidays to all.

Here, a few holiday screenshots taken this month from the Westinghouse H840CK15.



A work I did for the holiday.

[etype2]

Happy New Year to all.

2025 Rose Parade on a 1954 Westinghouse color tv.

[old_tv_nut]

Beautiful!
Happy New Year!

[ChrisW6ATV]

Very impressive indeed!

[etype2]

Posted March 3, 2025

A few screenshots from last night’s live Academy Award show on a Westinghouse H840CK15.

[oldtvman]

Are there any visual comparisons between the CT 100 and the Westinghouse?

[etype2]

Originally Posted by oldtvman

Are there any visual comparisons between the CT 100 and the Westinghouse?

Difficult to answer. Do you mean a characteristic common to one and not the other?

The CT100 is said to have a superior color demond circuit, beyond that, I’m not aware of design philosophy in the Westinghouse or RCA that make a difference, however this video states the Westy has no crystal oscillator and a few other differences. https://videos.files.wordpress.com/H...-rca-ct100.mov (Mt set does not drift) All things being equal, I think it largely depends on the original build quality at the factory and quality control. Some 15GP22’s suffer vacuum leaks, while others do not.

I think ultimate picture/color quality depends on the quality of the restoration/calibration.

[old_tv_nut]

Originally Posted by oldtvman

Are there any visual comparisons between the CT 100 and the Westinghouse?

There should be stronger color detail for orange and cyan colors in the CT-100, but I think it's nearly impossible to see with ordinary pictures on the small screen of the 15GP22. Both sets demodulate to the nominal NTSC colors for coarser details.

I have seen CT-100s that appeared to have weak color matrix tubes or out of spec components that clipped the signals driving the CRT, for example with the yellow in a test pattern getting desaturated towards white. I also note that when ETF had three CT-100s in a row, they all had somewhat different color. I think it could be explained mainly by set-up accuracy (white color was different) plus to some extent old components being out of tolerance.

The specs on the 15GP22 show a rather wide variation in cutoff voltage and drive requirements from tube to tube. Cutoff can be adjusted rather easily by eye, but white point is very difficult to get correct without a photoelectric color meter, so if that needed to be adjusted after the set left the factory it would probably have a wide variation. This was made worse by the huge difference in drive level between R, G, and B required by the 15GP22. Red gain had to run full blast while green and especially blue had to be cranked way down. Pictures would often end up too blue when adjusted by eye, which was evident in the side-by-side sets at ETF.

[Yamamaya42]

Red at full blast? : It's any wonder that any of the 15GP22s are still alive today!

[dtvmcdonald]

On a properly adjusted CT-100, with all the responses (RF, IF, color amp, and the I and Q filters) set up properly, with the infamous bad white peaking coils properly replaced (not easy! ... the specified replacements are wayyyy off) the difference in I and Q colors is not just obvious, its blatant. The screen resolution is much better than the I bandwidth. See the pictures of test patterns I posted years ago, some using exactly correct generator bandwidths.

At times the CT100 at ETF has been good enough.

As I have said before, for just one channel the CT-100 has 81 different adjustments. They all need to be right. This takes either love or paranoia, or both.
My set has the RF for channels 3, 4, 7, 10, 12, and 39 set with love. Other
VHFs are just OK.

[Penthode]

Originally Posted by dtvmcdonald

On a properly adjusted CT-100, with all the responses (RF, IF, color amp, and the I and Q filters) set up properly, with the infamous bad white peaking coils properly replaced (not easy! ... the specified replacements are wayyyy off) the difference in I and Q colors is not just obvious, its blatant. The screen resolution is much better than the I bandwidth. See the pictures of test patterns I posted years ago, some using exactly correct generator bandwidths.

At times the CT100 at ETF has been good enough.

As I have said before, for just one channel the CT-100 has 81 different adjustments. They all need to be right. This takes either love or paranoia, or both.
My set has the RF for channels 3, 4, 7, 10, 12, and 39 set with love. Other
VHFs are just OK.

I too battled through the process of ensuring the I, Q and Y responses were okay. Recall I made my own peaking coils or modified others to secure proper Y, I and Q responses. In addition I went through the demodulator operations and I checked the matrix resistors and settings and the RF IF response. I checked each VHF channel to confirm response. Comparing the chroma resolution and colour gamut with my other sets, the CT100 does have a sharper picture with better color. I see saturated deep yellows on the set which my friends say is quite remarkable.

Fotrunately the 15GP22 is very much alive but despite that tends to be dim. I have the chassis of the CT100 out on the bench right now as I prepare to construct and install my vertical convergence transformer replacement.

FYI: Yesterday I identified the AGC problem which had plagued me eg the tendency to overload on strong signals. I traced it to the resistive divider feeding the video amplifier screen. The lower end of the divider opened, raising the screen voltage. This in turn forced the video amplifier to conduct more heavily and lowered its plate voltage. The plate of the video amplifier is DC coupled the the 1/2 6AN8 horizontal sync separator which is dc cathode coupled the the grid of the other 1/2 6AN8 AGC keyer. the reduced coupled dc level to the AGC keyer grid inhibits proper agc keying. Replacing the video amp screen resistor restores the the dc level to the agc keyer and the CT100 no longer has the overload problem!

I apologize for the digression. When I have finished with the convergence fix, I plan to spend more time analysing the color perfomance.

[old_tv_nut]

Originally Posted by Penthode

FYI: Yesterday I identified the AGC problem

Nice sleuthing!

[etype2]

In this video of the CHRS Antique Event in 2024, https://videos.files.wordpress.com/H...-rca-ct100.mov the presenter mentions H.A. Poehler as a contributor. That is me! I don’t where the presenter got that name, but he used 23 articles from my website, including an authored article. https://visions4netjournal.com/westinghouse/

The video gives a presentation on the differences between the Westinghouse H840CK15 and the RCA CT-100 which address Larry’s question.

https://visions4netjournal.com/wp-co.../IMG_2593.jpeg

https://visions4netjournal.com/wp-co.../IMG_2592.jpeg

[etype2]

UPDATE:

First: I’m glad to see VideoKarma back up and running.

Posted September 22, 2025

Six Years.

Another year has passed since the completion of restoration of our Westinghouse H840CK15, six years ago on September 29, 2019. I want to take this opportunity once again and thank Mike Doyle who restored the chassis with recap, alignment, parts repair and replacement while I restored the cabinet. Mike also replaced the flaking aguadag coating over the 15GP22 CRT. The Westinghouse is holding steady with strong, stable performance. I don’t have much new to report since last year, so at this time will post the below screenshots photographed the last few days for judgement on the performance.

[old_tv_nut]

Nice! Thanks