RCA CTC4 Seville Restoration Near Completion (chassis)
 

Well after a year and half of recapping and educating myself I finally am wrapping up this project :huge:. It came with decent purity and I haven't touched the rim magnets around the screen yet., just needs degaussing and a few other touches. Will be taking a more formal video not using an antique mirror soon. This is my first color set. For the last few weeks I was unaware one can't just inject a video signal into this chassis, HUGE contrast and brightness changes once I got the tuner functioning properly yesterday. Most of the noise in the latest ones is my cheap shop DVD player or the camera.

http://hagstar.phanfare.com/7138833

John H.

Interesting. Can you give more details about your tuner (what was wrong, what you did to improve it)?

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Hey Ya, John! Hadn't heard from you in ages. :wave:

I remember Hagstar from rec.antiques.radio+phono many years ago. That's a newsgroup I've been reading for about 20 years. Ancient history.

Be sure to check out his pictures of the radios at the link he provided. He does very good work.

Well as received the tuner was vexing- it passed the color bars and dots etc. fine BUT was blind and deaf to actual video. For a week or so I failed to read your article and didn't know about the 16 volt video injection thing- results on-screen were muddy from injecting the standard 8 volts, assumed I needed a brightener. Meanwhile I was in the queue here to join. FINALLY I stopped procrastinating and demounted the tuner this past weekend. I took a thin test tube brush and denatured alcohol to the contacts, let them dry and squirted the contact disks sparingly with DeOxit. I also checked the resistors in there. Quite a bit of work getting the cover back into shape- it had been bent up by folks not wanting to take it off. Thanks to the article I did it the right way and suddenly had way too much signal- I still haven't throttled the Blonder Tongue modulator back enough yet.

Thanks everyone, Old Coot especially. He helped me get hooked on this with my first TV, a Crosley from the 2002 AWA Rochester meet which I still have.

John H.

You say there is too much signal. Have you tested the Blonder Tongue modulator on a different known working TV before? If it works right on another TV but over drives the CTC-4 then you need to adjust the AGC control on the CTC-4, NOT dial back the modulator.

The AGC control is unable to a handle the full signal well, adjustment was way too critical with 45 db of signal which has to be ten times design.

John H.

Ahh, so you are piping the blonder tongue RF directly into the tuner through coax and a balun....That would cause overload.

I prefer to use my Blonder Tongue modulators as transmitters. With a dipole tuned to the mid band of the channel the 40dBmV ones are capable of ~200' range on most vacant channels, and the 60dBmV ones can do a block radius.

As a fellow CTC-4 Seville owner I'd like to ask you for detailed measurements of the stand/legs portion of your set's cabinet....Mine is missing the stand/legs.

BTW/FYI: dB is a measure of relative signal strength, and without the reference point is meaningless to anything but gain/attenuation. DBmV is a unit of power and is not relative.

Yes I am aware of this. In saying 45 db I was referring to the specs and model number of my modulator only, not an accurate power level. I merely intended to give some rough perspective on level.

John H.

Well, it sounds like your tuner benefitted from cleaning. I love simple solutions.

If you are getting a strong clear picture with good colors, you may be near the declare-victory point. Some bits in old color roundies are better left alone unless you have a very specific reason.

I was one of those folks using rec.antiques.radio+phono 20 years ago, as well. Learned many things from that group, although I drifted away after web-based forums became more active.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

"First, do no harm." Yes, although I'd love to learn how to use my Triplet sweep generator better I fear the irreplaceable nature of many of these parts, like I have to tell you Phil :sigh:. Now with a CTC9 I'll be more game. I will likely however align the tuner to 2016 standards- to work best on Channel 3 :) At night I wrestle with questions like- if one aligns the tuning for stations which will never exist is it actually aligned? In fact did the alignment even occur?

John H.

Need to be more specific on the word "alignment". Sweep alignment of the IF strip is the very last thing to consider. Alignment of the tuner generally amounts to nothing more than setting the local oscillator so the fine tuning control covers the correct range on each channel.

But since the digital-changeover debacle, all the channels are moot except for the one(s) you want to use.

Well the manual has two pages on tuner alignment, warns you not to touch it without a sweep generator and 'scope. It wants you to match the response curve shown in Figure 46a by adjusting two transformers
and a variable cap. Then check each channel and determine an average expected gain.

I dunno. In some 30+ years in the trade, I never once had to sweep align a tuner. Nearest thing to alignment was setting the LO to the proper channel numbers.

Once in a while, a minor tweak of the mixer plate coil was needed to improve the color passband. The CTC-4's tuner doesn't have a mixer plate coil in the usual sense, though.

A by-the-book tuner sweep alignment would be 'waay overkill unless somebody has twerked with adjustments other than the LO.

You mentioned something to the effect of "being blind and deaf to actual video". Does this mean that with the color control fully off, the display shows no luma (BW video) signal? (With color fully off, normal BW video should still be there.)

Before the tuner began working perfectly after cleaning it was passing just the test generator's signals- all of the patterns. Now it pumps so much into the IF I had to throttle up the AGC a lot.

Oh I tend to agree about sweep alignment. I was just going to examine the curves, I have to bet it's performing fine to judge by the way it's receiving a faint analog image still transmitting on one channel of my cable feed that runs outside near it.

John H.