#346
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Another idea: Spend $800, buy the Hallicrafters CTC4 clone McVoy just listed on ebay, spend untold hours working on it, then compare waveforms!
Then you'd have a CTC-4 and a real rarity. |
#347
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Quote:
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__________________
Yes you can call me "Squirrel boy" |
#348
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I hate to cry Uncle, but I don't think I can take this set any farther without getting it aligned. I contacted the local collector club and asked if they know anyone in the Pacific Northwest who would try that if I delivered the chassis (or the entire TV), but got no response.
When I move the fine tuner, there is a very broad area in the middle of its travel where you bring in a fine B/W picture. You can only get color (true color, if it's a good day, or rolling bars, if it's not) at the opposing extremes of the tuner's range. This occurs on different channels, not only one. On other sets, I have bypassed the tuner/IF and injected video and audio directly, but injection is not such a simple matter in a CTC-4, if I understood Pete's earlier remarks correctly. I guess I'll wheel this guy out of the shop and work on something else for a while. Regards, Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html Last edited by Phil Nelson; 07-13-2015 at 05:43 PM. |
#349
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__________________
Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#350
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Quote:
http://antiqueradio.org/art/BROADCAST_NEWS_0656_4.jpg Pete Last edited by Pete Deksnis; 07-13-2015 at 10:09 PM. |
Audiokarma |
#351
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Quote:
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#352
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Well, that seems worth a try. At least it would be easier to evaluate the chroma circuits if I knew I was working with a clean input.
Thanks for the tip! Phil Nelson |
#353
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Phil, I think the solution is to learn to do alignments. Its not exactly easy,
but you can do it. Just one hint: before you do anything else, get a respectable set of calipers, good to a few thousandths of an inch. Measure and write down the position of each adjustment. For thinngs that are inside, like hollow cores, stick a plastic rod into the can and measure how far it sticks out. That way you can always restore to where it is now. Get a generator and scope and do it. A CTC-4 is easy ... except traps, which are set and forget, it has only 5 adjustments for the IF, one per can. |
#354
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In the second 21CT-660 preamp schematic from the Broadcast News article, no values are given for the coils L1, L2, L4 and their associated capacitors.
A note says: L1C1, L2C2, L4C3 -- RCA stock no. 75251 Any guesses as to these values? I don't have references for those part numbers. Presumably each of these was a coil with a cap wired in parallel. Regarding L3, the note identifies it as "North Hills coil no. 120 I set at 400 mu-h," so I suppose I can use an adjustable coil around that range. Regards, Phil Nelson Last edited by Phil Nelson; 07-14-2015 at 12:43 PM. |
#355
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My Merit cross reference shows that the RCA 75251 can be replaced by a Merit TV-151, 4.5MHZ sound trap. It gives no specs though for the part. There are probably Thordarson and Miller replacements as well. Hope this helps.
__________________
Tim |
Audiokarma |
#356
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Quote:
(2) In defense of the adapter, before building my first adapter for a CT-100, I reasoned that it was not distorting history because it was RCA who, at the infancy of color television, designed built, and used them. (3) Phil, I do not have the skill set needed to mathematically determine the missing LC values from CTC4 alignment procedures and the circuit, but I'm hopeful it can be done. (4) Thanks for the info Tim. Pete |
#357
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I found a source who has two of the three 4.5-MHz sound traps that I would need to build this preamp. In the schematic (below) they are L1C1, L2C2, L4C3.
I am wondering about substituting a modern component for coil L3, which is described as: "North Hills coil no. 120 I set at 400 mu-h" I see variable inductors at sources like mouser.com, but I'm not sure what (if anything) might work. Regards, Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html |
#358
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The problem is that you don't know if modern or even NOS specified
replacenemt parts are in fact exactly equivalent. In my CTC-100 restoration I found that for the notorious white coils they were not. Do you have a scope and sweep generator? If so, you should play with various parts to get a good result. This will result in you learning how to sweep and play with parts in a non-stressful situation. You are unlikely to find an adjustable 400uH coil in a modern catalog. Try Playthings of the Past and look in old Miller or Meissner catalogs to see if they have what you need. A Miller 6195 will work. |
#359
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Miller 6195 -- thanks for the tip. PTOP is the outfit that has 4.5-MHz traps in stock. They also have the Miller 6195 coil and they suggested another that might work, so I ordered them both.
Phil Nelson |
#360
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Phil, could you please measure the L and C of the traps when you get them?
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
Audiokarma |
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