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Old 09-08-2017, 04:15 PM
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wa2ise wa2ise is offline
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Join Date: Dec 2002
Location: USA
Posts: 3,147
Modified a RCA XL100 CTC108 TV w CH CM7000 inside

Had an older RCA XL100 TV set that used a mechanical click twist tuber (not a varactor or synthesized tuner). And had an extra Channel Master CM7000 CECB with S-video output. I decided to make this TV into a digital ATSC receiver by removing its old tuner and installing the CECB inside it. What this would do for me is to create a color TV set with no cross luma cross chroma defects (no false color crawlies on fine luma detail, and no crawling or hanging B&W dots on color transitions in the video image). What I worked hard at RCA labs to reduce with the then broadcast analog NTSC TV signals. As the Channel master CM7000 provides S-video outputs (the luma and chroma never been merged together, thus no cross signal defects later). Downloaded the SAM's ($22 but was worth it to find my way around the TV circuits) and found the points to inject the S-video and the notch filter on the luma I'd want to remove. Paid attention to be sure the demodulated chroma would match the luma on the display screen CRT. Also had to figure out how to get the audio into the sound IF demod and audio amp chip.

And took a picture of the resulting display:

No cross luma or cross chroma problems, as these were never mixed together in the first place. Digital TV ATSC transmissions keep these signals separate.

The CTC108 chassis is a "hot chassis" design, so I used a special antenna RF coax connector that stops DC and low frequency AC, but lets pass 50MHz and above from the antenna to the box (which is now "hot" inside this modified set).
Attached Images
File Type: jpg ctc108-cm7000front.jpg (98.7 KB, 128 views)
File Type: jpg no-cross-luma-chroma.jpg (100.0 KB, 263 views)
File Type: jpg modifiedCTC108.jpg (77.6 KB, 233 views)
File Type: jpg modifiedCTC108inside.jpg (39.3 KB, 93 views)
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