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Not Quite Sure What To Call This
I'm not sure what term to use when describing the problem in the picture below. Any time there is a white to black image, the white will "bleed over". Smearing? In any case the picture below was the best (worst) image I could find to produce this problem. Can any one tell me what this problem is called, and what the possible causes of this problem might be?
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#2
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Nobody have an idea? I have to say I can't guess why.
Also hard to see exactly what the symtpom is ...Hard to tell if the white bleed is actually starting AFTER the first line of white letters and continuing onto following lines, or is across the whole first line as well as every line. Can you do anything to the controls that changes it? If so, that might lead you to the section causing trouble. Other than that, no clue. Any change with fine tuning? If you have spare tubes, I'd try changing IF, video amp, AGC, sync separator. What set is this? |
#3
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There is no AGC in the set btw. This set is my 630ts. I don't know if it is apropos to this problem but the contrast control on this set seems more like an on/off switch. There is only three different settings- no video- weak contrast- good contrast. Other sets that I have are more of a gradual even ramping of the contrast level from no video to over driven. I've begun checking the resistors around that area and all are good so far. |
#4
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Hi All;
I would say check the Video section.. The video amp is not flat in its amplification of the video signal.. It remind me of a too narrow bandwidth.. But, it could be the IF section if it is not wide enough to carry the full bandwidth.. Thank You Marty |
#5
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Hi all;
In my other book with pictures,, it says possible causes for trouble.. Contrast control set too high, overloading the the amplifiers.. Video IF amplifier wongly aligned, with the video IF Carrier too low on the side of the response curve.. Faults in the Video Detector and / or Video Amplifier circuits.. Check coupling capacitors, decoupling capicators and bypass capicators for open circuits.. Check Plate Load resistors and grid resistors for incorrect values or shorting.. Amplifier grid biases may be insufficiently negative allowing grid current to flow.. Those with more experience, might be able to elaborate.. THANK YOU Marty Last edited by Geist; 02-16-2013 at 09:20 AM. |
Audiokarma |
#6
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would be interesting to see if you could see it on a scope. Need a fixed image of course and then look at each line of data (horz scan rate) compare the composite video to the output of the detector,then trace thru to the CRT grids (or cathode if that is how it goes).
Did you try a composite video injection at the video amp grid (sorry if you mentioned it already)? Maybe just a weak CRT that the cutoff is not that sharp. |
#7
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That's a correct assessment. The absence of any appreciable ringing or smearing-out of fine detail in the pic would rule out misalignment of the IFs.
The problem is almost certainly in the video chain. Have you checked the peaking coils for continuity? Looks to be eight of 'em sprinkled from the detector and the CRT. If they're all good, injecting with your B&K point by point thru the video chain (attenuating as necessary) oughta spot the problem. Quote:
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I have another 10BP4 that doesn't give me as good a picture as this one. It displays the symptom as well.
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Unfortunately I don't 100% trust my B&K at the moment. I think it needs some servicing of it's own for a few reasons. It's quite a shame as this is precisely what it is good for. That will be my next project on the bench. Quote:
I think I'm going to go resistor hunting in my video section and see what I can find. |
#9
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The Picture control on a 630TS is confusingly named. It is a manual gain control and its effect is not like a contrast control on newer TVs.
The Picture control varies the gain (i.e., amount of amplification) on the overall signal. You may find that it has a pretty narrow range where the picture & sound are acceptable. You may also need to readjust the Picture control when changing to a different source with a weaker or stronger signal. To some extent, what you're experiencing is normal for a 630TS. At one end of that control's range you'll get almost no signal, and at the other end you'll get wackadoodle picture & sound. Bear in mind that 1940s TVs were designed to be watched in dim lighting. I suspect we're all guilty from time to time of cranking the controls up too high and expecting these old sets to have an ultra-bright screen like modern TVs, that you can watch in a sunlit room. There was a recent thread in another forum by a guy who had similar horizontal lines (on a different television) that looked like overdriven video. I think they disappeared when he removed (or changed?) a modification he had installed to minimize retrace lines. On a general note, if you go treasure hunting to check resistors, check mica caps, too. Micas used to be thought immortal, but now more and more of them are found faulty. When I redid my 630TS 1,000 years ago, an oldtimer told me to replace the mica coupling caps in the video IF chain. Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html Last edited by Phil Nelson; 02-16-2013 at 02:21 PM. |
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Audiokarma |
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http://www.videokarma.org/showthread.php?t=257163 His symptom was different -- full-width horizontal lines with some vertical folding -- and you don't have a retrace mod to un-install, but the discussion may be mildly interesting. If you haven't already done so, may as well follow up on old_coot88's most recent suggestions. Phil Nelson |
#12
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http://www.youtube.com/watch?v=jmCvh9sm0Wg Would this point to a malfunctioning picture control pot? |
#13
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If this was a solid-state TV, I would say it has bad electrolytic capacitors in the video circuits. Double-check the values of the capacitors replaced in those circuits.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
#14
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I have also been restoring my 630TS and after the replacement of all the paper caps, all the electrolytics, and all resistors out of tolerance by more than 7% I recall seeing a similar (if not the same) image while using my little 5AXP4 test CRT. Unfortunately I did not take any pictures of that problem. Since then I have spent several days struggling with the video, audio, and tuner alignment. This is my first attempt at aligning a tuner, so I could be completely wrong. Most of my struggle was with the tuner alignment which ended up being solved by carefully selecting the 6J6 tube that worked best (alignment sweep response pattern wise) in each of the three tuner 6J6 positions. It went from only getting a weak picture and no sound of channel 3 on tuner channel 4 to getting a good picture and good sound of channel 3 on tuner channel 3 and channel 4 on tuner channel 4. I found that I had to perform the video and audio alignment again after the tuner alignment to get the video and sound right. The final video alignment was able to flatten the response curve, but not as good as the alignment figure in the procedure. Here is an picture after the final tuner and IF alignment. Its not well focused yet but I do not seen any smearing now. I still need to go over the horiz/vert linearity and size adjustments once the chassis is back in the cabinet.
Last edited by Zenith6S321; 02-16-2015 at 06:32 PM. |
#15
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Hi All;
I like what your screen says -- Your TV or its cables are NOT HD -- .. That says it all.. THANK YOU Marty |
Audiokarma |
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