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David_Web
Joined: 02 May 2007
Posts: 418
Location: Sweden
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| Posted: Sun Jan 03, 2010 7:55 pm Post subject: Composite into old TV? |
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Sort of OT but I hope you don't mind 
I have an old DUX TV that is BW. Unfortunately it only has a tuner.
So I would like a way to input composite into it.
However I don't really know how. I have followed the output of the tuner and tried to inject the signal directly but that did not work. (well I had to experiment didn't I  )
I might have done it wrong or the signal is different.
I know an RF-modulator would do the trick but I don't want to buy one.
Although I do have a few old VCRs that I potentially could scrap, but I'd like it to be a small box in that case and not the full VCR. Maybe even fit it inside the TV. So that is an option.
I'd like to keep the 12V input for portability in that case, but I guess that's not a problem.
Any ideas?
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Jan 03, 2010 8:16 pm Post subject: |
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Normally the video is injected into the jungle ic, but I dont know what you have as in age of device and such. Got a model number?
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David_Web
Joined: 02 May 2007
Posts: 418
Location: Sweden
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| Posted: Sun Jan 03, 2010 9:27 pm Post subject: |
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As I said, I don't want to buy one. I'd rather go through all the hassle of modding or not at all 
Type: DX 31 T 007/19
220V 50Hz 35W
NR: PM 231840
I could post a picture tomorrow.
I guess it's from 1970-75 or so but no way to be sure.
Draws a whooping 9W and goes up to 11W with a bright picture.
Time to break apart some VCRs I guess. They need to be thrown out anyway.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Jan 03, 2010 9:58 pm Post subject: |
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I got na da.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Jan 03, 2010 10:04 pm Post subject: |
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If I had a print I could help ya but I have no idea of what you have in there.
Some of the old tv's had a schematic label on the inside of the cover. Some even had a loose folded paper inside with schematics. Anything there?
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RVonse
Joined: 09 Mar 2006
Posts: 3152
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| Posted: Sun Jan 03, 2010 10:17 pm Post subject: |
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Composite is what goes into the video amplifiers after the IF amplifiers. The reason hooking composite did not work from the tuner output is that that tuner signal still is rf modulated ibecause it is still in front of the IF amp. You had the right idea but you just picked the wrong spot. You needed to get it patched after the IF and into the 1st video stage.
If it is a 70's set it will be no prolbem at all for you. Everything should be big, spread out, and easy to patch. Should not cost you dime to rewire.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Jan 03, 2010 10:40 pm Post subject: |
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Let me also point out that the composite is also carrying the sync and it would also depend on where these signals are separated is this design.
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David_Web
Joined: 02 May 2007
Posts: 418
Location: Sweden
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| Posted: Mon Jan 04, 2010 12:41 pm Post subject: |
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Sorry about the bad images.
http://yfrog.com/5dimg1655ejx
So I have to find the stage where the signal is unmodulated but yet not stripped of sync.
The knob at the back is to set scanrate so it has a very narrow span of which it locks on to.
You can see the hole I made for the BNC at the back above the antenna input.
I think that the silver(shield) with gray middle part cable at the bottom left next to the antenna inputs the the output from the tuner. That's where I tried to inject the signal at least.
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