SCART problem with Ferguson TV set
 

Dear friends, this is my very first post! I'm Marcus from Brazil...

I have a Ferguson TV set, it works perfectly with my classic BBC computers (via a especially installed DIN socket which was professionally done at stores back in the day), but, whenever I try the SCART socket, no matter what source, I get a reddish "background", although the other colours seem OK. This happens only with SCART. It's not the SCART cable though, I tried several to the same result.

The attached files show the normal picture (Beeb) versus the reddish ones (ZX Spectrum). Any ideas?

Also, there's a VIDEO button on the front, other than RGB, but there's actually no video socket on the back...

Please, help!

Re: SCART problem with Ferguson TV set
 

I suspect broken or dry solder joints on the SCART connector. These were prone to breaking and that's why I'm not a big fan of SCART. If you wiggle the cable, does the picture restore to normal?

Re: SCART problem with Ferguson TV set
 

Thanks for your reply, I did that but it didn't work. :(

Re: SCART problem with Ferguson TV set
 

In that case it's probably going to be a matter of opening up the TV to check the state of the wiring to the socket.

Re: SCART problem with Ferguson TV set
 

Thank you very much, Dave. I'll have a friend do that for me, I'm not into Electronics. :thumbsup:

Re: SCART problem with Ferguson TV set
 

Hello Marcus,

I don't remember these sets, but would the DIN socket be expecting TTL level, 0-5V RGB signals? I think that's what these home computers sent out.

Are you saying this set has both DIN and SCART connectors?

A SCART socket is expecting much smaller 0-700mV RGB signals, so maybe the old computers are over-driving things. If only the Spectrum had this red tint, I'd suggest a small fault in the Red channel on the Spectrum was appearing as a big red signal to the more sensitive SCART input stages. However, you say the Red tint is on all SCART pictures, which would suggest a minor TV fault, sadly.

If you still get 'snow' on the screen if you select the video channel, then maybe that button is just designed to give a more stable picture from a VCR wired with an RF lead into the aerial socket.

If the screen goes black when you select the video channel, maybe the set is expecting composite video on SCART pin 20. This would be on the yellow socket if you've bought a SCART to phono/RCA/Cinch adapter.

Other people here may have worked on these sets back in the day and have a better idea than me.

Good luck.

Re: SCART problem with Ferguson TV set
 

Some TV manufacturers cheaped out on the SCART connectors, and relied only on the soldered connections to the motherboard to support the socket, instead of riveting it to the board and/or screwing it to the outer case of the set. It did not help that, by dint of the form of the set not making it easy to turn around, one was often having to work by feel just to insert or remove the SCART plug.

In the event of loss of sound in one speaker, or weird colour problems such as complete loss of blue, the advice was always the same: Re-solder all the pins of the SCART connector. Moving the plug in the socket will not always restore the broken connection. Once I overcame my phobia of TV sets, I fixed a few with this simple method.

The SCART connector is designed to be able to accept a full composite colour video signal with blanking and sync (CVBS), or it can accept an RGB signal and use the CVBS input only for timing. If the earth return for the red signal has become disconnected, that could cause your problem. The BBC Micro's RGB output is suitable for connecting to a SCART input with just a few resistors and two diodes; a TV repairer could fit a suitable DIN socket, but it and the SCART socket should not both be connected at the same time -- permanent damage is very unlikely, but weird visual effects are practically certain!

Re: SCART problem with Ferguson TV set
 

I'm not familiar with that TV, but have seen something similar on an early scart Sony portable.

This would work fine on scart RGB, but scart composite (same socket) would produce a very colorful picture from 'some' satellite receivers.

Adding a 75 ohm resistor from pin 20 to ground cured the problem for the Sony, but for other TV's, adding 75 ohms in series with pin 20 cured identical issues.

Take all the usual precautions if you open up the TV, optionally, add 75 ohms in the lead if there's space.

From memory, my old workshop had a scart connector with a toggle switch & resistors to 'select' series/parallel or off, for the 75 ohm resistor. Crickey, that was a while back!

I still have a Sony portable from the early 90's, cracking picture on Freesat HD! (RGB).

Mark

Re: SCART problem with Ferguson TV set
 

Since every colour has its own ground return, I'd start by checking these for loose connections. Red uses pin 13.

Re: SCART problem with Ferguson TV set
 

Nice looking TV and cabinet!

Re: SCART problem with Ferguson TV set
 

Its a TX85 isn't it? The scart was a seperate board fitted through a knock-out on the back panel?

The BBC gives out, in addition to UHF, RGB TTL I think, I'm sure that's what the corresponding Microvitec Cub would've been on a DIN socket. The standard Sinclair Spectrum only has UHF but had an unofficial mod for composite video which ought to be scart compatible. TTL normally requires divider resistors hidden inside the scart lead but the guy who fitted the din input to the Ferg would've scaled it appropriately.

Re: SCART problem with Ferguson TV set
 

The BBC Micro does indeed output at TTL levels. To cope with this I made up a lead with series resistors to attenuate the signals down to the 1V P-P required by the SCART on the TV/monitor I used with it. I don't remember off-hand what value I used, and would need to open up the plug to check if the information is needed.