View Full Version : RCA New Vista


csingle
05-14-2008, 07:41 AM
Good Morning, All.

I have in my living room an RCA New Vista Model CF315M. It is a great daily watcher, except in the last six months, the Vertical Linearity has gotten off a bit to the point where people have cone heads. Any adjustment to the pot in the back has resulted in a worse condition than it was before I adjusted it. I really noticed it last night watching "Woman in the Window" with Edward G Robinson.

Anyway, I digress. I am in search of a schematic or any thoughts on which part of the circuit might be at fault. If you know of anyone who m ight help, I would appreciate it.

Thank You,

-C.S. Ingle

Old1625
05-14-2008, 08:10 AM
Bear in mind that the vertical size control can also affect linearity. Both controls need to be tweaked alternately, until you can be sure the top and bottom edges of the raster are just off the screen phosphor, and that the lines are evenly spaced from top to bottom. This takes a bit of practice.

If no combination of adjustments of the 2 controls corrects the problem then the vertical oscillator/output tube(s) would bear examination and replacement as needed.

If none of the above correct the problem then you need to go deeper into the circuitry and check for capacitors becoming leaky or changing value out of tolerance. Resistors need to be checked as well.

truetone36
05-14-2008, 04:21 PM
What is the chassis number on your set?

bgadow
05-14-2008, 10:32 PM
746-4 should be the Sams number. I would almost bet that you have a bad capacitor in the vertical circuit. I would just replace all of them in that section.

csingle
05-15-2008, 07:44 AM
I tinkered with the set last night and replaced two tubes, which then caused an awful picture. Changed one of them back and adjusted the deflection magnets on the yoke. This resulted in an incredibly clear sharp picture. However, based on the fact that the tube I didn't replace caused problems when installed, I would say that there is still a problem in the circuit. I think it was a 6CF7.

The picture is REALLY good right now, but every time there is white lettering on the screen I get an annoying buzz through the audio section that will not go away with adjustment of Sync Sep or the AGC.

Anyone have any thoughts?

-Chris

mattdavala
05-15-2008, 09:41 AM
Ratio detector adjustment will help get rid of that buzz whit those high contrast scenes. Check your schematic to find out which can on the top of the chassis is the ratio detector.

Best regards,
Matt Davala

csingle
05-15-2008, 10:28 AM
I would check the schematic, but I have no means of acquiring it as the Library threw the SAMS out years ago. Might anyone have a copy that I might obtain by E or Snail Mail?

Thank you,

-C.S. Ingle

csingle
05-18-2008, 11:17 AM
Finally got around to posting some pics of my Living room set here. Hope you like. Quality is actually better than the pics show, as I used a cell phone camera to take the pics.

-Chris

Old1625
05-19-2008, 04:23 PM
Nice picture! :thmbsp: It would appear that the pix IFs are all very well tuned, as the picture looks very sharp.

Keep in mind that some of those old sets had a "buzz" or "noise" adjustment for the audio, and that a quick tweak of that particular poteniometer was the magic to keep the white lettering out of the sound path. I might've mentioned possibly a fine tune adjustment would be the first step, but it would appear by your image that the video is optimum at that setting....

wa2ise
05-19-2008, 06:24 PM
When Microsoft fixes the bugs in its Vista operating system, will they call it "New Vista"?

:D Running, ducking for cover :D

ChrisW6ATV
05-20-2008, 01:05 PM
Is it coincidental, or related, that RCA used the "New Vista" name around when "nuvistor" small tubes were available? I don't think my New Vista TV has a nuvistor in it, but I did have a UHF converter with one in the 70's.

bgadow
05-20-2008, 10:30 PM
No coincidence-they were named that way on purpose. Most New Vista sets have a nuvistor but some of the later ones don't.

csingle
05-21-2008, 01:15 PM
I don't believe mine has a nuvistor that I can see, but since they are "small" (HAHA) it could be hiding anywhere. I've still got the sound turned all the way down and running it through the external stereo, but the buzz is still there on the set if I were to turn it up.

Don Lindsly
05-21-2008, 01:58 PM
That TV uses a quad detector like a 6HZ6, or something. The quadrature coil needs to adjusted for minimum buzz and distortion. It will only need a half turn in either direction. You will notice a big difference.

It is a small coil next to the sound detector tube and takes a plastic hex tool. Do not use an Allen wrench or anything metal. The slug will break. It is not usually in a can, but may be in an uncapped square shield.

The can on the other side of the 6HZ6 may need touching up, but the quad coil usually fixes it. Don't touch anything else. That set will have clean sound from off-air channels, when tuned properly.

It does use a 6CW4 nuvistor for RF amp in the tuner. It is a very small metal tube that is located between the larger tube and the antenna connection.

peverett
05-21-2008, 09:33 PM
Also be sure that the detector tube has high emission. I had a set with buzz. The detector tube was testing in the "questionable" range, just below good. When I replaced the tube with a NOS one the buzz was gone.