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 Post subject: Odd Tuning Issue - 1984 JVC Color TV
PostPosted: Aug Sat 28, 2021 8:08 am 
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Joined: Aug Sat 28, 2021 7:56 am
Posts: 2
Hello everyone,

First off thank you for allowing me to join your forum, I am joining from overseas in Europe, and I would like to ask for your advice on a strange issue with an old TV.

The TV in question is a JVC 7808EE (from what I understand this was their export model to Eastern Europe at the time) and the TV is from 1984. I have all the original manuals, schematics, etc, basically I got it almost free from the original owners, it is good enough to watch the morning news on :mrgreen:

The issue I am having is - when I turn on the TV, the first channel tunes normally, the picture is clear. If I change to any of the other channels, the screen is all snowy and the sound is bad. The strange part is that to fix this, I just need to unplug the antenna cable, and plug it back in, with the TV turned on. Then everything is fine. So something is obviously wrong, but I would like your opinions on what. The tuner is digital, and I am getting regular analog signal from our apartment building's TV cable.

My first thought was that something is wrong with the antenna cable in the building (not grounded or something?) but the TV acts the same way with a VCR, so the issue will be with the TV itself.

Any thoughts on where to look for the issue will be very helpful, I have basic electronic skills, nothing super advanced but I would like to try to fix this simply to see if I can :-) Thanks in advance.


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 Post subject: Re: Odd Tuning Issue - 1984 JVC Color TV
PostPosted: Aug Sat 28, 2021 10:22 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 10034
Location: Redlands CA
Possibly the fine tuning is slightly off, when you unplug it and plug it back in it might be close enough for the AFT to pop in.

I found a picture of this set here https://www.radiomuseum.org/r/jvc_7808_ee.html

This type of tuner appears to be the type that can be set to any channel on any button, you set the outer ring to UHF or VHF and the center small knob tunes it in, (I think, it's been 40 years since I had to set one up).

You might try turning off the Auto Fine Tuning if it has that, then turn the center knob that corresponds to the button and see if it'll tune in. Each channel has to be set up individually. If this is the problem then you should only have to turn it a tiny amount.


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 Post subject: Re: Odd Tuning Issue - 1984 JVC Color TV
PostPosted: Aug Sat 28, 2021 3:13 pm 
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Joined: Mar Tue 03, 2009 11:12 pm
Posts: 2022
Location: Great Bend KS
This reminds me of when Zenith had those little slide switches inside the control panel door to set the AFT off on and special. Many a time people always thought either they were special or their tv set was, and they had the thing set to special and the set wouldn't always lock on to the channel selected.


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 Post subject: Re: Odd Tuning Issue - 1984 JVC Color TV
PostPosted: Aug Sat 28, 2021 9:37 pm 
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Joined: Aug Sat 28, 2021 7:56 am
Posts: 2
Thank you both for the advice - and yes this is exactly that TV. Any of the 8 presets can be set to any station that is available.

I tried this before as well (the AFT switch is the same switch that pops open the door to the tuning knobs), so I've tried this with it off, and fine tuning the channels (almost endlessly) and no improvement. One more odd thing that may give someone a clue - sometimes when tuning one of the presets with the fine tuning knob (the inner one), I cannot get a good enough picture, but if I move the outer knob and then move it back, the picture becomes clear (for example tuning in UHF, I move the bigger knob the VHF and back to UHF. This is all with the AFT off).

Could it be as simple as taking out the tuner and cleaning the selectors with some contact spray? Somehow this seems too easy, but may be worth a try.


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 Post subject: Re: Odd Tuning Issue - 1984 JVC Color TV
PostPosted: Aug Mon 30, 2021 7:24 pm 
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Posts: 3082
Location: Hayward, California USA
Here is a test to try: Connect snd turn on the TV set, and it the picture is good on that channel, now open the tuning door (which should then tutn off AFC/AFT). Is the picture still good? If not, make sure you can tune it in with the control for that button. Also, now, tune the control (without hitting a different button) and confirm that you can also find other channels with good picture and sound. Put the control bsck to the original channel (still without trying any other buttons) and verify it is still good. Now, hit one or more other buttons, then hit the original button again. If the picture is bad, can you fix it with the tuning control? Also at this point, try finding other channels with the tuning control as you did before. If they are all gone or weak, then the tuner itself may have a problem associated with AGC. That may be tougher to find or fix.

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Quote: (Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did.


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