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#31
10-02-2010, 02:54 PM
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Quote:
Phil Nelson 
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#32
10-02-2010, 06:40 PM
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I found that the bending a the top of the screen doesn't occur on the cable channels, so I'm thinking it's definitely the VCR. Also, that double horizontal image only happened with those cartoon tapes. Later I turned the set back on to show a friend, and I didn't get that problem then, either.
As for the brightness and contrast, I can get the screen to become fairly bright by cranking up the brightness... but increasing the contrast virtually does the same thing. It just becomes brighter until everything is barely recognizable. Turning up the screen register does the same, and I've tried various combinations with only a few rather poor compromises. The only way I could get decent contrast was to turn the screen register way down and then turn up the brightness, and the contrast would improve somewhat. However, turning the screen register down increases the buzz so badly that the image begins to jitter horizontally. So, the pictures I took appear fairly dark because I have the picture set to the best compromise between picture and sound. I have three NOS 6CB6 tubes on the way for the IF section ( GE brand for $1 a piece ) and I'm hoping that might help the buzz at least. I had just read somewhere that a washed-out, low-contrast image was sometimes the result of a bad video amp tube. So, unless there's no truth to this, I might consider picking up another 12BY7. Last edited by RitchieMars; 10-02-2010 at 07:11 PM.
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#33
10-04-2010, 05:33 PM
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Still buzzy...
The picture has improved significantly...
 The bad news is that the new IF amp tubes didn't help. Actually, it seems that when I change channels, the horizontal goes nuts and all the sound goes away, then after about 30 seconds or so, it eventually all suddenly comes back. All the audio is really distorted depending on the channel, and the buzz is still prevalent. I guess I'll get back to hunting through resistors and ceramic caps.
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#34
10-04-2010, 11:11 PM
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I believe poor alignment can lead to that symptom-where it takes a minute for the picture to sync when you change channels. Your set is really turning out like the first 21" I restored-an RCA tabletop. For the longest time, I just had this faint washed-out picture, but as I replaced more and more bits, it came together.
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#35
10-05-2010, 12:15 AM
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If you totally ignore the audio (turn it down) and adjust for best picture, is there a combination of picture controls that gives you a nice image? Good contrast, brightness, focus?
Phil Nelson
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#37
10-05-2010, 03:36 PM
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Well, one thing I noticed is that the control I was calling the "screen register" is actually the A.G.C. delay. The A.G.C. isn't labeled on the control panel and it's right next to the screen control, which is unused. It's just an empty hole?
So yeah, I can get better contrast by bringing the A.G.C. delay down ( darker but more contrast ) and turning then turning the brightness up. However, the lower the A.G.C. goes, the louder the buzz, and to a certain point, the horizontal starts to jitter really bad. Last night, I figured out how to auto-program the VCR and use it as a cable box. The television's tuner may be out of alignment, but at least I can get channel 3 cleanly enough to flip through the channels on the VCR without much trouble. Many channels still need a bit of a tweaking to get the buzz to a moderate level ( fine tuning, buzz control, etc ) to where it's not perfect, but certainly watchable. Where would these peaking coils be located, if I do indeed have one that's potentially open?
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#38
10-05-2010, 03:52 PM
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I would also double check the capacitors in the video output circuit for correct value and wiring...it looks to me as if you get a decent black at the edges of a transition to a black area but it does not last, as if there is a cap somewhere in the circuit is too small a value. Does this set have DC restore circuit?
jr
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#39
10-05-2010, 08:21 PM
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Here's something I was wondering about ever since I recapped my set...
 To mount these two filter capacitors I used the lugs of two of the vertical output tube's unused pin sockets. It was convenient this way because I could still arrange that 470 ohm resistor between them and send them both to a common ground, which is also being shared with a 47uf from the audio output tube. The big 80uF filters from the low voltage rectifier, and the 30uF filters pin 8 of the audio-out. I just thought I'd mention this in case there's a chance that there might be a problem with this arrangement. It concerned me that there might be something about the close proximity of these unrelated tubes/circuits that could cause any of the problems I've had. None of the capacitors I replaced are of the wrong values. A couple of the 40uF have been replaced with 47uF, which should be fine. If I'm reading this right, however, this .002 should be a .001?  Oh, unless this was the .001 I was looking for...?  There's three red "domino" caps in this set. Never dealt with them before. Anyways, I was able to watch some tv on my set last night and today with some buzz here and there. If I played old movies from the DVD player, it worked fine. But if I put in something more modern, there were sudden scenes of bright to dark and everything got buzzy. I just pulled the chassis back out again and I found a 100k resistor between the contrast control and the video amp tube that was reading about 40% out of spec, so I replaced that. I'll let you guys know if I find anything else. Oh, and I'm not sure about the DC restore circuit. I can scan some of the schematics if it would be of any help. Last edited by RitchieMars; 10-06-2010 at 05:19 AM.
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#40
10-06-2010, 06:27 PM
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YouTube video of my set playing...
Here's a clip I recorded earlier today after making some adjustments to the yoke and centering rings. I still don't have the contrast I want, and the buzz is still there on some DVD's and the cable channels, but I can certainly tune it out well enough to play these black and white movies!
http://www.youtube.com/watch?v=ofUCT57sfRM
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#41
10-08-2010, 01:26 AM
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Intercarrier Buzz
Here's what my Ryder's manual for this set has to say about sound alignment:
"1. Tune in a tone modulated TV signal and adjust the step attenuator until the signal is reduced to a level where "hiss" is heard with the sound. 2. Adjust the sound take-off coil L19 ( top and bottom slugs ), intercarrier coil L22, quadrature coil L2 and buzz control R39 for the cleanest sound and minimum buzz. It must be remembered that any of these adjustments may cause the "hiss" to disappear and fruther reduction of the signal will be necessary so that the "hiss" does not disappear during alignment. If intercarrier buzz is in evidence, after all normal sound adjustments have been made, the cause may be attributed to one or more of the following: 1. Improper adjustment of the AGC delay control. 2. Defective 6AU6 sound limiter 3. Extremely high signal levels which require attenuation of the antenna circuit. 4. Transmitter over modulation." I think I should locate these adjustments and have a look at it. The most believable fault here to me would be the 6AU6. I just cant imagine that these adjustments were ever in need of changing from the factory, so I get the impression there is a component failure that's pushed this out of alignment. The contrast issues are another story...
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#42
10-08-2010, 07:19 PM
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[QUOTE=RitchieMars;2984260]The picture has improved significantly...
AYEEE! Michael Cogdill on WYFF!!! That set is going to look GREAT!!! The 6AU6 is not expensive, either.
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#43
10-08-2010, 08:18 PM
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Lookin' good
 I think you're in the homestretch.
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#44
10-09-2010, 05:08 PM
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Quote:
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#45
10-09-2010, 07:05 PM
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Its a small world. My sis and brother in law have a place in Simpsonville.
I think you're coming down the home stretch now!
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