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  #46  
Old 11-17-2021, 07:16 PM
W.B. W.B. is offline
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Originally Posted by W.B. View Post
As I'd noted in earlier posts, the color circular test pattern design (first unveiled in 1965) originally had two variations, coded by region as per the order of a diagonal black/white wedge at the bottom of the outer lower right quadrant. TP's with this layout:



were for stations east of the Mississippi with 'W' calls; five stations were confirmed to use it - KYW Channel 3 and WIBF (later WTAF and now WTXF) Channel 29 in Philadelphia, PA; WCMC (now WMGM) Channel 40 in Wildwood, NJ; WFLD Channel 32 in Chicago, IL; and WNDT (now WNET) Channel 13 in Newark, NJ / New York City (the last actually confirmed to be color). And as laid out here:



was for west of the Mississippi with 'K' calls. Only one station, to date, has been confirmed to use it, and then with a B&W print: KAET (Channel 8) in Phoenix, AZ.

My question is, how many "old-timers" on this forum remember either layout, and who else would've used either prior to the wedges at bottom right being eliminated? Certainly those stations weren't the only ones . . . ?
Turns out that the second one in order on this post was the earliest known variant. One other TV station is confirmed to have used it: KYW-TV itself, during its last full year (1964) in Cleveland while Westinghouse Broadcasting (Group W) owned the station.


And the other zigzag wedge dated at the earliest to 1965:
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  #47  
Old 09-29-2022, 08:46 PM
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TK-1 update: I have had the TK-1 and 2F21 CRT now for some time. Sorry for the very slow updating, but there are definite prerequisites before proceeding to the next step of troubleshooting and a repair.

Just recently, was kindly provided the manual for the WP-33 low voltage (main) power supply. That's important because the power supply will have to be duplicated from a performance standpoint to get the precise voltage regulation required at the TK-1, which is on the order of that from a laboratory power supply.
The WP-33 supplies all of the circuits for H and V deflection, oscillators, in/out, and video signal processing, as well as a 3 Volt DC source for centering the raster via yokel connection.

Also got a replacement HV transformer for the 2F21 circuit itself, as that and other things are missing from the TK-1 chassis, and there was some butchery of the high voltage section in the TK-1, perhaps a last ditch attempt to keep it running or resurrect it?

The HV power transformer for the CRT was/is known anecdotally as a 'weak point' on that chassis. A TV museum a few hours away has a TK-1 in working order and has had to make up their own HV supply using an oscilloscope transformer. That is a good solution and I assume their HV is regulated.
Despite finding a good transformer, I have to find the root cause and go from there to prevent the original problem if at all possible.
This transformer and its rectifier and filter produces a DC voltage of around 1800V which requires very close regulation so that its output is not modulated by line-voltage fluctuations and other minor disturbances like CRT current, lest the scan dimensions on the target plate change.
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Last edited by Opcom; 09-29-2022 at 09:03 PM.
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  #48  
Old 09-30-2022, 11:33 AM
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Did you intend the TK1 post for a different thread?
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  #49  
Old 10-02-2022, 02:01 PM
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Quote:
Originally Posted by W.B. View Post
Turns out that the second one in order on this post was the earliest known variant. One other TV station is confirmed to have used it: KYW-TV itself, during its last full year (1964) in Cleveland while Westinghouse Broadcasting (Group W) owned the station.


And the other zigzag wedge dated at the earliest to 1965:
Cleveland's NBC affiliate, WKYC-TV on channel 3, used a test pattern similar to this one when the station was an NBC O&O in the '60s-early '70s, showing the NBC "snake" logo in the lower right corner; the station may have kept the same test pattern, with few if any modifications, until it went to 24-hour operations. The call sign and channel number were in the top left corner of the test pattern; however, to the best of my knowledge, the black and white wedge was never used, even after the station was sold from NBC to a local company in the mid-'70s.
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  #50  
Old 05-01-2023, 09:25 PM
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The first of those early TP's (with the zig-zag black/white wedge at bottom right) was also used (albeit represented in B&W) by WBOC-TV in Salisbury, MD.

By the mid-1970's, WKYC switched to electronic color bars, and NBC didn't unload it until the mid-'80's.
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  #51  
Old 05-01-2023, 10:06 PM
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Joe Roizen on test charts:

https://www.youtube.com/watch?v=CCzWsa7l6qo&t=8s
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