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#1
10-11-2009, 10:25 PM
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VCR messing with TV
I have been watching my CBS- Columbia tv for a while now and everything seems good. I borrowed a tested -good scope and used it to calibrate my set. But if I watch any vhs tape the top 1/3 of the screen is pulling bad and horiz. hold won't touch it.dvd's are fine.Regular cable is fine. I have used said vcr on another tv(solid state portable) and the pic is fine.What causes this?
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#2
10-12-2009, 09:30 AM
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Your TV needs a modification to speed up the horizontal time constant. Was a wery common problem back when VCRs first came on the market in the '70s and were connected to older TVs. What you are seeing has to do with the combination of the horizontal timing in your TV which was designed before VCRs, and skew error from the VCR. VCRs will have some skew error from one field to the next as it makes a frame. On a machine playing its own recorded tape this usually is not a problem. But with tapes recorded on another machine or many pre-recorded tapes, depending on how precisely the two heads for field A and B are aligned on the drum exactly 180° from each other, there can be some timing error as head A hands off to head B. Also back tension and other mechanical alignment can effect it.
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#3
10-12-2009, 10:18 AM
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I have seen time base correctors at reasonable prices and they will stop this.
Using schottky (hope I spelled that correct) diodes in place of the dual diodes in the horizontal phase detector circuit can stop or greatly helps eliminate this problem.
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#5
10-12-2009, 06:52 PM
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And the JVC SR-V10U. That VHS will fix anything including chroma noise.
__________________
“Once you eliminate the impossible...whatever remains, no matter how improbable, must be the truth." Sherlock Holmes.
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#6
10-13-2009, 12:24 AM
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The other night I decided to fire up my 1956 Philco for the first time since analog signal ended. With the old analog signal the TV worked perfectly, and with no antenna.
First I hooked up a VCR which dispayed a viewable, but snowy picture on channel 3, and a little better on channel 4. Then I brought in the DTV converter which I thought would be clear as a bell. WWRROONNG!! The DTV was TERRIBLE. Not snowy but just all choppy (not pixilating) and weird looking. I really can't explain it. Even the audio was barely listenable. I have done no further investigation since. I did acquire an extra matching transformer as that could cause issues. I hope it's that simple. I should not be having these troubles, since the set was receiving fine before. I hate this because my Philco has always been there working when nothing else would. The best set I have ever owned. It has played nearly flawlessly for me for the past 26 years. I assume it must have done well between the 50's and the 80's.
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#7
10-13-2009, 08:43 AM
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Quote:
John
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#8
10-13-2009, 10:52 AM
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Quote:
http://www.antennaweb.org/aw/Address.aspx After the switchover, I experimented with various antennas and even built one, seen below. I have resigned myself to the situation and don't even try using antennas any more. There's nothing worth watching on local TV, anyway. As an alternative, I got a Blonder-Tongue AM60-550B agile modulator for $26 on eBay and use it to transmit from our satellite receiver to any TV with rabbit ears in the house. I can't comment on the quality of RF output from various converters. Our Zenith box seemed to work fine, on TVs new and old. Phil Nelson 
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#9
10-13-2009, 11:17 AM
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I've had trouble with a VCR on my '72 Zenith 20CC50 color set. On both VCRs I've tried I lose horizontal hold on the t.v., yet I have no problems with the DTV converter box.
__________________
Dumont-First with the finest in television.
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