Did RCA use WB IQ after the CTC2/Bs.

[Tomcomm]

So far only the CTC 121 and CTC136B were suspected to have used WB IQ chroma demodulators. Wayne states he evaluated the performance of a RCA CTC13X that had WB IQ demodulators but gave no details of its implementation; did it use a NEC IC? A whole bunch of guys say they have or had either CTC 136Bs or the CTC121s which also is claimed to have WB IQ processing:
CTC136B stromberg67 Kevin
CTC121 zenithfan1 Mark, waltchan, zenith2134, wa2ise, nrx37, blast
Surely at least one of these has a schematic or other documentation that definitely proves the CTC136B or CTC121 used WB IQ and how it was implemented. Since I have a CTC2B open on the bench I would appreciate any information why RCA tried WB IQ on only a couple of CTVs and quickly dropped it. Thanks, Tom

[zenithfan1]

I have the service manual for my CTC-121, I'll look into what it says. I know for a fact it's IQ but it's been a while since I read the details. It was just too complicated and they thought in the '80s that they had the technology to try it again but it just wasn't cost effective IIRC. Like I said, I'll look in the book and see later or tomorrow.

[zenith2134]

Hey, that's '2134 to you! sorry, I don't have the schematic

[stromberg67]

Hi Folks: I have the SAMS for my CTC-133B open in front of me, and the chip designated "U 700" , a 42-pin DIP, shows I and Q demodulators and amps, and the integration of luma and chroma signals on the chip. I haven't had the chassis out for service for a number of years, as it still performs amazingly well for a 24 year old, but I do believe the chip(s) are marked NEC. The color detail in the picture is very sharp, and many different shades of red are visible, and very distinct from red/orange hues. A very enjoyable TV to watch.
The RCA part number for the chip is 176225, and no sub numbers are listed, so maybe the chip was proprietary.
The only repairs to this set have been a resistor open on the CRT board, and a blown audio output IC. Looking for parts chassis' now.
Thanks to all for YOUR postings.
Kevin

[Tomcomm]

[QUOTE]Hi Folks: I have the SAMS for my CTC-133B open in front of me, and the chip designated "U 700" , a 42-pin DIP, shows I and Q demodulators and amps, and the integration of luma and chroma signals on the chip.[QUOTE

Kevin.........That CTC133B schematic is a great find! The RCA number 176225 crosses with Hitachi, maybe its the same chip? The fact that it combines luma and chroma at low levels instead of at the CRT is great. It's probably why you get such great color detail. I bet there's a lot of inductors and caps around the chip to do all the required filtering in analog. Is there any way you can scan or photo the small schematic portion around the chroma demod chip? Can you PM me for my email address. If the chip is available ($5.00), it would be fun to attempt to build up the circuitry and try it out. Thanks, Tom

[zenithfan1]

My interest is peaked now, I'll dig that stuff out tonight and have a look at the CTC-121 as well. We should take some pics so we can compare chassis too.

[stromberg67]

Hi Tomcomm I scanned a few pages from the SAMS, which is #2513, and hope they can offer some insight. It looks like the logos on the chips have been covered or removed, why I don't know, so U700 could be Hitachi.
Let me know if you want more scans.
Kevin

[andy]

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[andy]

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[stromberg67]

Good suggestion, thanks. I wasn't sure that they would look right. I'll try to make them bigger later, but maybe not tonight. Much to do with family today. I'll email them to myself until they seem OK for the forum.
Kevin

[Tomcomm]

Originally Posted by andy

Make your pictures bigger. They can be up to 900x900.

Sorry Kevin, I couldn't read any of the chip block diagram lettering, which is probably the most revealing info. I think 900 X 900 pix should read fine. Thanks, Tom

[amptramp]

Originally, the I signal was 1.5 MHz bandwidth and the Q signal was 0.5 MHz bandwidth. A television that made use of both bandwidths would have both a luminance delay line and an "I" signal delay line to ensure the signals arrived at the same time at the CRT. Otherwise, I and Q demod is just like R-Y, B-Y but with different matrix values.

CTC-2 forever!

[Tomcomm]

Modern CTV to me is when they went solid state. That's when I lost TV interest and knowledge. Perhaps WB IQ didn't work so well after the CTC2/B was due to the fact the later CTV had fewer IF stages than the original six. When they got down to three stages they couldn't get the flat responce and precise uniform phase delay required for WB IQ without artifacts, so they stuck with NB R-Y B-Y? Rediscovering WB IQ really fascinates me and others. Sort of cultish,eh?......Tom

[andy]

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[kx250rider]

There were several I & Q sets made in the 80s, including that CTC-121 (or 120?). Also isn't the Sony Indextron I & Q?

Charles