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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 12th Jul 2008, 10:16 pm   #1
Gonzini
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Question JVC Videosphere Composite Video in Mod

Hi all
Not posted in a while, good to see its still lively as ever!
Ive been given 2 JVC 3241 Videosphere tellys to try and modify.
Basically i need to get composite video straight in somewhere without using an Rf modulator if possible ( though that might be the easiest option )
Has anyone here tryed to do this on one of these or other, i could do with some ideas.
I dont usually do much with tellys either which doesent help, though i do have the schematics.
Cheers
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Old 13th Jul 2008, 7:59 am   #2
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Lightbulb Re: JVC Videosphere Composite Video in Mod

Hiya,

I've been looking at a similar idea with my two Ferguson 38030 and 38050 sets. I decided to leave them be, but when going into "Game" with my son, saw and RF modulator with sound for a Wii console priced down to 98p!!

I converted an old Sega master system one before. Generally when you cut the cable, you find a 0v cable, a +5v (or +12), an audio feed and a composite video. Plug it in and hey presto, composite feeds for your old telly for 98p!

Trev
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Old 13th Jul 2008, 12:00 pm   #3
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Default Re: JVC Videosphere Composite Video in Mod

Hi,
the rf modulator idea is better, and easier! saves having to make holes in the telly too. I bought a couple of the things Trickytrev mentioned, and they give very good results, the plug that's supposed to go into the games console gets removed, then I fitted a scart socket on the end of the cable, with the DC input also mounted inside the scart socket. the whole thing runs off a 5v supply, and I can run anything through it! and since their only 98p (mine were 4.99 from argos a while back..) their well worth a go!

regards,
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Old 13th Jul 2008, 1:38 pm   #4
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Default Re: JVC Videosphere Composite Video in Mod

Hi Trev & Lloyd
Cheers for the replies!
The modulator idea does sound too cheap a solution to not look at.
Im sure i have a maplin kit modulator in a box somewhere that i could try first.
I dont need to pick up any sound which is one less thing to think about.
Is this what you guys brought?

Nintendo Wii RF Modulator:-

http://tinyurl.co.uk/0fha

Their £5 online but i guess their selling them off in the shops for some reason.
I might have a look in the branch in Portsmouth if its still there.
Not bothered about fitting a BNC on the rear of the TV, i need to make it simple for the end user
This is partly the reason for the composite in as the TV could get detuned and i think their both going to end up hanging from the ceiling out the way.

Looking at the schematics there is a point after the video amp where the H & V syncing gets tapped off along with audio and video.
Could the composite video be injected around this area with a bit of signal conditioning?
Cheers
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Old 13th Jul 2008, 2:06 pm   #5
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Default Re: JVC Videosphere Composite Video in Mod

Picture : Try around TP4. Via a capacitor though - safety's sake!

Cheers,

Steve P.
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Old 13th Jul 2008, 4:41 pm   #6
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Default Re: JVC Videosphere Composite Video in Mod

Hi Steve
I was wondering if i would get away with injecting the composite video at that point.
I guess an electrolytic for decoupling with a value between 10uf to 100uf, whatever highest voltage i have in the draw will do?
These TV's are so compacted inside, hopefully l'll be able to get at that area of board easily.
I converted another one some time back, but that was fitting a TFT screen, that turned out pretty good.
See whats happens then!
Cheers
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Old 14th Jul 2008, 5:06 pm   #7
ALANS ANITAS
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Default Re: JVC Videosphere Composite Video in Mod

I don't know the set, but is the chassis isolated?

ALAN
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Old 14th Jul 2008, 5:24 pm   #8
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Default Re: JVC Videosphere Composite Video in Mod

Quote:
Originally Posted by Steve_P View Post
Picture : Try around TP4. Via a capacitor though - safety's sake!
Please make sure the chassis is isolated before even thinking about doing anything like this. If it isn't, then you can't safely do a video input without using an external isolating transformer. With all due respect to Steve_P (who does know his stuff) any capacitor that will couple video cannot provide safe mains isolation. You do want to use a capacitor but that's to prevent disturbance to the DC conditions in the video amplifier.
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Old 14th Jul 2008, 10:56 pm   #9
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Default Re: JVC Videosphere Composite Video in Mod

I think they are isolated, I'm pretty sure that when i opened mine up for cleaning there was a mains transformer, and it can run from a 12v battery.. so maybe run it off a battery while doing said experiment?! just a thought..

regards,
Lloyd.
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Old 15th Jul 2008, 10:32 pm   #10
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Default Re: JVC Videosphere Composite Video in Mod

Hi Gonzini, yes that's the exact one.. Seems to work well but I've only seen it in black and white up to now. I've built a combined breakout box and PSU for mine. The cables in mine are as follows: Screen=0v, black=+5v supply, Green=composite video, white=audio and red doesn't appear to do anything. I have terminated my video input with about 66ohms as this stabilized the display a bit more and took the audio through a 100nF cap.
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Old 16th Jul 2008, 12:23 am   #11
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Thumbs up Re: JVC Videosphere Composite Video in Mod

Hi guys
Thanks for all your safety concerns, its good to see your on the case!
Dont panic the chassis isin't live, its all tied to ground on the secondary of the mains transformer.
I wouldnt of attempted this if the chassis was wasn't isolated from the mains.

Anyway its works! Ive attached a pic as proof!
I think i need to attenuate / match the input a bit as it seems to satuarate when the contrast is set high, but other than that its a good stable picture.
Its a bit of a pain to get at that part of the PCB, things are very packed in.

Trev thanks for the info on the modulator, its useful info for any future projects like this, though i dont do much with TV's to be honest.

Cheers guys
Gonz
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Old 16th Jul 2008, 6:53 am   #12
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Default Re: JVC Videosphere Composite Video in Mod

Excellent! well done.

Picture does look rather good as well.
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Old 16th Jul 2008, 6:23 pm   #13
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Default Re: JVC Videosphere Composite Video in Mod

That's brilliant! pleased it worked out ok, you'll have to show us what exactly you did to it, I might have a go at it if it doesn't cause too much disruption!

regards,
Lloyd.
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Old 16th Jul 2008, 8:13 pm   #14
Gonzini
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Default Re: JVC Videosphere Composite Video in Mod

Hi Lloyd
Ok l'll take some pics, ive got 2 of these to do.
I need to tweak things a little bit to get rid of some nasty side effects of doing it this way, hopefully l'll have another look tonight if i get time.
The area of the main PCB you need to get to is near the bottom so you have to partly remove the board and metal screening can around the 3rd IF amp and video amp.
Other than that its looks like you dont have to touch anything else.
I might change the secondary supply fusing arrangement as the've fused the negative just before it grounds on the chassis
Also a new bit of 3 core mains cable is in order...
Cheers
Gonz
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