B&W Output From Modulator
 

When using a Mercury RF modulator connected to an early 70s Sony Colour set, some sources display in black and white. You can often see SOME faint colour present, but very little. For all intents it is black and white.

DVD player, VCR, all fine through the same modulator. But for example, modern Atari joystick with built in games and composite output - B&W.

Just curious the technical reason why this is and whether it can be rectified somehow?

Re: B&W Output From Modulator
 

Sounds like non-standard output from some devices (NTSC perhaps?) as modulator is performing correctly when fed with valid source
It might help to list the ‘non performing’ sources in order to diagnose further

Re: B&W Output From Modulator
 

Thanks. I did wonder if it was NTSC, but one such device was used on the composite input of a 90s CRT and that showed the colour fine. Which if it was NTSC I believe it would not?

All of the devices so far have been gaming related. Atari 2600 joystick with built in games, like this https://www.amazon.co.uk/Atari-Retro.../dp/B076BS5WVN

and lots of similar and cheaper devices. "Retro FC Handheld" for example, which is a "NES on a chip" device with a load of games on flash memory. All cheapy tat, which might explain why it doesn't work so well. Just curious as to the technical reason and if they could be made to work better

Re: B&W Output From Modulator
 

What Sony TV is it? I’ve got 2 KV-1330’s which have trouble with some sources, I use a Toshiba VCR DVD combo as a signal source, when playing a DVD it works fine, and VHS tapes too, but some freeview boxes and my Sumvision SD card video player show incorrect colours on the Sony’s. I put it down to the simple PAL decoder used in them not decoding substandard colour signals correctly.

Regards
Lloyd

Re: B&W Output From Modulator
 

Many recent TVs, both later CRT & LCD etc had multi-system, auto switching decoders which decoded and displayed correctly virtually anything thrown at them - causing not a little head scratching for the poor unfortunate trying to diagnose a fault

Re: B&W Output From Modulator
 

Its a Sony KV-1320.

I guess the colour coding is present on the composite signal and that colour system is passed through the modulator to the TV. So I guess it cant be fixed, interesting to know however.

Knowing very little about televisions Id have expected a composite signal was a composite signal, clearly theres more to it and TV manufacturers have instead decided to accommodate all sorts of variations over time. Interesting

Re: B&W Output From Modulator
 

It is quite likely the source, the Atari joystick. Either the colour sub carrier is slightly off frequency or the chroma is low. Sony sets are particularly fussy about this.

When I worked in the cable TV industry no colour faults from customers when it appeared OK leaving the headend always seemed to be those with Sony TVs. The fault at the headend was something like a poor connector causing the chroma to be very low.

Re: B&W Output From Modulator
 

Modern TVs seem very fussy about conformity to standard. I suspect that, in the analogue days, tolerance of design was essential due to component production spread. In this digital age some jobsworth digital circuit can just say 'sorry, that is 0.01% out of spec. I'm not accepting it'.

My daughter couldn't use her old game console on her new TV. I concluded that the TV didn't like the game console's non-interlaced output.

There has been a passion in recent years for taking the schematics of classic consoles and using libraries to put them verbatim onto FPGAs or such like. The result is non-standard outputs from 'modern' hardware.

Oh, for good old fashioned, tolerant, easy-to-use, gracefully degrading analogue TVs!