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Old 09-27-2016, 08:07 PM
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Streaks shooting across screen

My 1973 Chromacolor and 1977 Trinitron show short, multi-colored streaks shooting across the screen when playing a DVD. They usually show up one at a time and cross higher and higher before starting again from the bottom. I thought it was an issue with the Zenith until I fed my Trinitron with the same setup. This does not happen with my 1987 Electrohome, so it must have something to do with the design of the older sets. What gives and is there anything I can do about it?
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Old 09-27-2016, 10:06 PM
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A picture is worth a thousand words...There are lots of things that could cause it, but without a picture it is hard to know which are relevant to the particular streaking you have.
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Old 09-27-2016, 11:19 PM
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Capturing a photo would be very difficult so I shot a video while paused on a blank frame. It happens whenever the player is on, I don't need to be playing a disc.

https://youtu.be/hj7fZG3Rho0
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Old 09-28-2016, 01:02 AM
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It looks like electrical interference from an outside source, the fact that two sets do the same thing seems to confirm that, possibly the DVD player itself or something in your home.

The Electrohome may just be able to reject it better.

You used to see this type of interference back in the days of rooftop antennas when a car with a leaky plug wire would drive by.

Try another DVD Player, if that doesn't work start unplugging devices like Wall Warts and Computers.
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Old 09-28-2016, 05:23 AM
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Old 09-28-2016, 07:07 AM
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Quote:
Originally Posted by Eric H View Post
... start unplugging devices like Wall Warts and Computers.
+1. You would be amazed what can cause interference. We had a service call at work for an audio system in a spa. It would buzz and crackle randomly. I scheduled a time when they were closed and started replacing gear. After I replaced everything and the problem still persisted I stared unplugging their equipment. Finally I unplugged the machine that was supposed to shoot ozone (or something like that) onto your face. The machine wasn't even on, but as soon as I pulled the plug all the interference went away.
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Old 09-28-2016, 07:54 AM
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Definitely looks like 60 Hz AC related. I notice a band of the interference takes about 17 seconds to go up the screen and start over at the bottom.
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Old 09-28-2016, 08:11 AM
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Reminds me of noise I've seen from some electric motors.
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Old 09-28-2016, 08:17 AM
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I remember the exact same thing 30 years ago on my grandparents' TV, which was connected to a rooftop antenna.
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Old 09-28-2016, 02:24 PM
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Looks like motor interference, as noted. Do the sets with the problem have 300 ohm (twinlead) input and the set that is OK have coax? Second the idea of unplugging things, but the first things to check would be motors. Do you have forced air heat? Does it go away when the circulating fan stops?
Do you live in an apartment or duplex? It could be your neighbor's heating system fan motor.
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Old 09-28-2016, 02:57 PM
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The Sony has a coax input. The interference is always there.

I've killed power to just about everything else in here and switched the signal source with no difference. I'm in an apartment and the only heating systems I know of are electric and hot water baseboard heaters.

Last edited by Jon A.; 09-28-2016 at 03:00 PM.
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Old 09-28-2016, 03:12 PM
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It could be line interference. I don't know where to suggest you get a line choke. Some of the more expensive computer power strips have interference chokes between the string of AC outlets. If you can get your hands on one of these, you could try plugging your receiver into it.
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Old 10-19-2016, 12:36 AM
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Even the 1987 Electrohome started showing interference, and the 1976 Electrohome console did shortly before I swapped it in as our daily watcher. However, I noticed as I moved the coax cable going from the RF modulator to the TV the problem got worse. I thought "Ahhh, so it's the coax picking up the interference!" I got the shortest cable I had on hand, a jumper for an old cable converter box, about 3" long, and just let the modulator hang off the set. Presto, interference gone.

Last edited by Jon A.; 10-19-2016 at 12:40 AM.
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Old 10-19-2016, 11:24 AM
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Quote:
Originally Posted by Ed in Tx View Post
Definitely looks like 60 Hz AC related. I notice a band of the interference takes about 17 seconds to go up the screen and start over at the bottom.
Yes.

The noise burst creeps upward because the field rate was changed to accommodate NTSC compatible color television.

NTSC sends about 59.94 frames/second, but our utilities still use 60.00, the motion is a result of the difference

(1) over (60.00 - 59.94) = 16.666.... seconds.
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Old 10-19-2016, 01:21 PM
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Quote:
Originally Posted by Robert Grant View Post
Yes.

The noise burst creeps upward because the field rate was changed to accommodate NTSC compatible color television.
Yes and no. It was part of the color standard, but for a dumb reason. IIRC the color signal did not play nice with the sound sections of some older RCA models (RCA had kept their sound circuits primitive too long because of their cheapskate patent use policy) and so to 'fix it' they shifted the color carrier frequency slightly which HAD to be mathematically locked to the scan rate...So the scan rates got dragged along for the ride.

It was within tolerance of sync on receivers of the day so no one cared, but once VTRs became big and time code for tape was in the works engineers cursed at the scan rate change endlessly.
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