Vintage TV with RF modulator - UK Vintage Radio Repair and Restoration Discussion Forum

zawoblondon · 4th Nov 2019, 7:26 pm

Hi,

I want to be able to see video from my DVD in an old TV (70's).

At this moment I'm connecting the composite video cables from the DVD into a RF modulator.

Then coaxial cable from the RF modulator to an UHF transformer.

And the UHF transformer is connected to the TV old TV antenna.

The RF modulator is set to work at the channel 50, so I set the TV to show that channel.

For that channel the video signal is just showing 2 shades of grey separated by a vertical line at the middle.

The setup is the same others are using to make it work, so I'm not sure if I'm doing anything wrong or it's just that the TV itself is not working anymore?

Any help is much appreciated.

I attach some photos of the hardware.

ben · 5th Nov 2019, 2:20 am

Inter - that's a long disappeared Spanish brand name. Where did you get it? It is likely Pal -B/G, not Pal-I, as found in UK analogue equipment.

It could be that the output level is too high from the modulator, have you tried turning it down a little?

Post a picture of the back of the set with the connections so we can see exactly what goes where.

The TV could of course have a problem or misadjustment in the sync or tuner I suppose. Try adjusting the vertical or horizontal hold controls, usually on the back of the TV set.

simpsons · 5th Nov 2019, 10:45 am

This modulator is quite clever and will provide sound for both UK and European model TV's. In addition, both video, audio and RF levels are adjustable. It has a test signal facility which is accessed via the unit menu. A YouTube video in Spanish explains how to set it up.

Given the problem is vision, l suggest this needs to be addressed first.

My first impression is that the TV is seeing an unmodulated video carrier. Your hook up seems right so first set the modulator to produce the internal test signal. See from the manual what is expected. If necessary use a second TV to confirm that the all is well. Make sure the test signal is then turned off.

Some DVD players, through the menu, expect the user to switch between RGB and composite should the Scart socket be use. Should it be set to RGB there will be no composite output. Check the setting.

The preset adjustments on the modulator should be adjust according to the instructions.

Chris

julie_m · 5th Nov 2019, 3:57 pm

Quote:

Originally Posted by simpsons

Some DVD players, through the menu, expect the user to switch between RGB and composite should the Scart socket be use. Should it be set to RGB there will be no composite output. Check the setting.

Do they? I have never known a DVD player like that.

The SCART wiring standard uses the composite video signal to provide the sync pulses in RGB mode, precisely to avoid this situation. If the set is unable to display an RGB picture, it falls back to displaying the picture from the composite video signal. And if there is any crosstalk, the "unwanted" information is being generated from the same RGB coming up the cable separately, and whatever is trying to break through will be the same as what the set should be displaying anyway.

Sometimes there is a menu item to select between RGB and S-VHS; the latter via SCART uses what would ordinarily be the "red" channel for the colour information and the "composite" video channel for a mono picture. A composite-only SCART input fed from an S-VHS source will still display a mono picture.

An RGB input would not be able to make any sense of such a signal; but the RGB switching line (on pin 16, if you ever have to disconnect it) would not be asserted with the output in S-VHS mode, so the set should fall back to displaying the picture encoded in the video signal.

At any rate, even connecting a DVD player in the "wrong" mode to a TV ought to give you enough of a picture to be able to see the on-screen menus and select the right mode.

peter_scott · 5th Nov 2019, 5:09 pm

The screen image looks like a possible test signal that the modulator generates to make tuning-in the television easier. I wonder if it generates this in the absence of a video input or whether there is a switch somewhere to select the source. Is the TV receiving sound signals from the modulator?

Peter

19Seventy7 · 5th Nov 2019, 5:44 pm

Going off what Peter said, it's simple but might help

My modulator has a similar effect on screen when there isn't a proper input signal. I can get sound with a blank grey screen, or I can get video with no sound.

Could there be a loose connection somewhere internally or externally from the source or modulator itself?

zawoblondon · 5th Nov 2019, 6:38 pm

Quote:

Originally Posted by ben

It could be that the output level is too high from the modulator, have you tried turning it down a little?

Post a picture of the back of the set with the connections so we can see exactly what goes where.

The TV could of course have a problem or misadjustment in the sync or tuner I suppose. Try adjusting the vertical or horizontal hold controls, usually on the back of the TV set.

I have tried turning the output and video levels up and down. It only affects to the noise of the image, but the two shades of grey still appear.

Quote:

Originally Posted by simpsons

My first impression is that the TV is seeing an unmodulated video carrier. Your hook up seems right so first set the modulator to produce the internal test signal. See from the manual what is expected. If necessary use a second TV to confirm that the all is well. Make sure the test signal is then turned off.

The test signal is working. I can see two vertical white lines over a black background.

Quote:

Originally Posted by peter_scott

The screen image looks like a possible test signal that the modulator generates to make tuning-in the television easier. I wonder if it generates this in the absence of a video input or whether there is a switch somewhere to select the source. Is the TV receiving sound signals from the modulator?

The TV makes some beep sound when the modulator is on test mode, but no sound on normal mode.

In normal mode (not test) the TV shows the same image whether the DVD is connected (and on) or not. The DVD works as I tested it in a different TV.

I attach an image of the test signal.

simpsons · 5th Nov 2019, 8:18 pm

I notice that horizontal bars superimpose the test signal.

What happens when you plug the modulator into the other TV?

What is the make and model of your DVD player?

Also, notwithstanding Julie M comment, are you using an adaptor to connect the modulator to the scart socket or is there a composite output from the DVD player which you are connecting the modulator to?

4th Nov 2019, 7:26 pm	#1
zawoblondon Retired Dormant Member Join Date: Nov 2019 Location: London, UK. Posts: 2	Vintage TV with RF modulator Hi, I want to be able to see video from my DVD in an old TV (70's). At this moment I'm connecting the composite video cables from the DVD into a RF modulator. Then coaxial cable from the RF modulator to an UHF transformer. And the UHF transformer is connected to the TV old TV antenna. The RF modulator is set to work at the channel 50, so I set the TV to show that channel. For that channel the video signal is just showing 2 shades of grey separated by a vertical line at the middle. The setup is the same others are using to make it work, so I'm not sure if I'm doing anything wrong or it's just that the TV itself is not working anymore? Any help is much appreciated. I attach some photos of the hardware. Attached Thumbnails

5th Nov 2019, 2:20 am	#2
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Vintage TV with RF modulator Inter - that's a long disappeared Spanish brand name. Where did you get it? It is likely Pal -B/G, not Pal-I, as found in UK analogue equipment. It could be that the output level is too high from the modulator, have you tried turning it down a little? Post a picture of the back of the set with the connections so we can see exactly what goes where. The TV could of course have a problem or misadjustment in the sync or tuner I suppose. Try adjusting the vertical or horizontal hold controls, usually on the back of the TV set. __________________ Regards, Ben.

5th Nov 2019, 10:45 am	#3
simpsons Octode Join Date: Feb 2007 Location: Harrow, London, UK. Posts: 1,493	Re: Vintage TV with RF modulator This modulator is quite clever and will provide sound for both UK and European model TV's. In addition, both video, audio and RF levels are adjustable. It has a test signal facility which is accessed via the unit menu. A YouTube video in Spanish explains how to set it up. Given the problem is vision, l suggest this needs to be addressed first. My first impression is that the TV is seeing an unmodulated video carrier. Your hook up seems right so first set the modulator to produce the internal test signal. See from the manual what is expected. If necessary use a second TV to confirm that the all is well. Make sure the test signal is then turned off. Some DVD players, through the menu, expect the user to switch between RGB and composite should the Scart socket be use. Should it be set to RGB there will be no composite output. Check the setting. The preset adjustments on the modulator should be adjust according to the instructions. Chris

5th Nov 2019, 5:09 pm	#5
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: Vintage TV with RF modulator The screen image looks like a possible test signal that the modulator generates to make tuning-in the television easier. I wonder if it generates this in the absence of a video input or whether there is a switch somewhere to select the source. Is the TV receiving sound signals from the modulator? Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

5th Nov 2019, 5:44 pm	#6
19Seventy7 Octode Join Date: Jun 2018 Location: Essex, UK. Posts: 1,307	Re: Vintage TV with RF modulator Going off what Peter said, it's simple but might help My modulator has a similar effect on screen when there isn't a proper input signal. I can get sound with a blank grey screen, or I can get video with no sound. Could there be a loose connection somewhere internally or externally from the source or modulator itself?

5th Nov 2019, 8:18 pm	#8
simpsons Octode Join Date: Feb 2007 Location: Harrow, London, UK. Posts: 1,493	Re: Vintage TV with RF modulator I notice that horizontal bars superimpose the test signal. What happens when you plug the modulator into the other TV? What is the make and model of your DVD player? Also, notwithstanding Julie M comment, are you using an adaptor to connect the modulator to the scart socket or is there a composite output from the DVD player which you are connecting the modulator to?