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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 11th Jan 2020, 10:18 pm   #1
EF80TVVALVE
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Default Philips TVette

Hi all,

I'm just working on one of these and whilst doing so I wondered if it is possible to fit RCA inputs for line video and audio. This set will be used more as a monitor for video recorders so it will make it easier to use if this is possible.

I've attached some photos of the appropriate areas of the schematic, I'm just unsure where would be best to fit line inputs in order for them to work well. For vision is it best to fit the input to the input of the video driver or video amplifier? For audio I presume the 0.1uF that feeds the volume control on the A.F amplifier will be where I feed audio. I will also add a switch to turn off the tuners on sound and vision so they don't interrupt the line signal.

Cheers
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Old 12th Jan 2020, 11:41 am   #2
Restoration73
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Default Re: Philips TVette

You might get noise from the if stages if the tuners are off.

Best to use a dp switch or (or switched sockets) to allow you to inject video via C2077
and audio via C2029. It is easy to add attenuation if signal levels are too high.
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Old 12th Jan 2020, 12:08 pm   #3
simpsons
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Default Re: Philips TVette

I am not too sure why you would want to do this. The T-Vette is a dual standard monochrome receiver and so VCR colour faults, for example, would not show up.

In addition, all VCR's with composite video out are 1.0 v (p-p) at 75 ohms, some using BNC connectors others Scart, either way you will need to build a suitable interface to break in to TV's video which is designed to work from the receivers detectors.

I would suggest far better you use the VCR's RF out into a colour receiver which, by design will have a true black level unlike the T Vette and almost all other monochrome receivers, which use mean level agc.

Adding 'video in' to a domestic receiver will not turn it into a broadcast monitor which, by design, is something else. I know, I have one.
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Old 13th Jan 2020, 3:04 pm   #4
GreasedMonkey
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Default Re: Philips TVette

I recently did something similar, but using a freeview receiver PCB mounted inside the set, as I wanted a monochrome, single box solution to watching modern TV signals.

By far the hardest part of the project was getting the set working in the first place.

I Added a switch to switch between the freeview signal and the sets own tuner (as I wanted to keep the original functionality for use with VCRs).

First stage was to get the set working correctly and then I could scope up both Audio and video signals and compare them with that coming out of the freeview PCB. Audio was pretty much bang on so that could be squirted straight into the sets own audio amplifier stage. Unfortunately the video was not so easy. I don't remember the exact details now, but I had to raise the signal by adding some DC offset and amplify it (Gain of 3 springs to mind but could be wrong). I built a simple 2 transistor video amplifier and clamp circuit which gave me the correct signals that the video stages of the set were 'expecting' and also a true and stable black level. This signal could then simply be injected into the video stages of the set.

As has been stated, the result is not a broadcast quality monitor, but a perfectly watchable TV.

This was my first Ever TV related project and if I can do it, anyone can.

I do have issues with the set currently, but that's another story.

Details here:
https://www.vintage-radio.net/forum/...d.php?t=154305
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