Binatone TV Master MK 4 Composite Video Mod

Binatone TV Master Console

Modern televisions have a digital tuner, and therefore the analogue UHF output from this console will not be compatible. Of course, the solution is to use the SCART video input of the television, however, this console does not have a composite video output socket.

I was analysing the PCB as shown in my earlier Binatone TV Master MK IV article, and discovered that there is a video signal (of sorts) available from the console.

Composite Video and Sync Pinout

As you can see in this chip pinout, pin 6, pin 9, pin 10, and pin 24 provide video output information signals for, ball, right player, left player, and score (plus field background) respectively, whilst pin 16 provides a sync pulse.

Composite Video

Composite video Circuit

On this Binatone console, these pins connect to a common point through their respective diodes D to combine the individual video signals. In addition, the synchronisation signal (pin 16) -- which builds the raster -- is also added to the same common point through a 1.8 kΩ resistor, thus forming a composite signal of sorts. Hence, the point where the signals merge is the most likely candidate to provide a composite video signal. Although this video signal will not be exactly to the SCART specification, it should be compatible up to a certain point. All one has to do is to tap off the signal from here and feed it into the SCART video input of the modern television. A one-microfarad decoupling capacitor in series helps.

Composite Video - Tapping Point

Component side of the PCB.

On the PCB, you can see the cluster of components, the four diodes, and a resistor, merging to a common point. Leaving the diodes and resistors in their position is probably a good idea, as the diodes help to protect the video output pins, and, simply tapping the signal from the common point will allow the RF circuitry to remain operational as well.

PCB Tracks and the point to tap the signal from.

Here is the common point from the PCB trace side. Due to a vast number of domestic televisions and their differing circuit designs, it would be difficult to determine how well this video signal displays on all the modern televisions. For example, how well a high definition TV would handle this signal is difficult to tell. An impedance matching problem may occur. Many televisions require the video signal to be precisely within specifications; otherwise, they ignore it, whilst others are more forgiving.

Video Signal Amplifier

Circuit diagram for the mod.

Although the video signal is not perfect and the picture quality may be poor due to the missing back porch, electrically it is almost compatible. A small one-transistor circuit could be used to bring the signals within the 5 V electrical specification, however this may not be necessary if the signal is already providing a clear picture for your model of television.

In this circuit, a commonly available voltage regulator (7805) is used to create a 5 V rail from the 9 V that the console uses. A commonly available transistor such as the BC547 is used to bring the video signal within the 5 V specification. A 75 Ω biasing resistor is also used, and the 4.7 µF capacitor provides decoupling.

Since modern televisions fix to a wall, a long SCART cable may be necessary, and therefore this circuit keeps the video signal strong, however it is optional. It is of course possible to connect the audio to the SCART plug as well as the video. The pinout connections for the SCART plug, in the Sinclair + article might help.

Power Supply

Power supply points on the PCB.

It is possible to take the power supply for the video circuit from the console power supply. The points shown on the PCB is where the power supply is applied. Of course, how well this circuit works depends upon the television. It will provide a clear picture on the older televisions that are 50 Hz at 625 lines. However, it would be difficult to guess how clear the picture would be on the latest receivers.

SCART Pinout

SCART Pinout showing audio and video pins.

This SCART pinout shows the pins for the video input, and audio input. This end plugs into the television and then you need to select the correct SCART port using your remote control.

This article is for experienced electronic engineers who are able to follow and understand. If you are not a qualified and experienced electronic engineer, then do not make this mod as you may damage your game and television.

Other Mods

This Binatone TV Master Mark 4 has had a few modifications and upgrades since I last wrote about it. Hence, I should call it Mark 4.1.0. I use it with a small black / white portable, which has a UHF tuner. It is usually out at Christmas time, and is great fun to play. I just love the old cathode ray tube telly and tuning in to the UHF signal as it is all part of the old retro experience that reminds me of the past. The flickering cathode ray tube... The smell of the valves and dust heating up... The high frequency whine of the field coils... Chestnuts roasting on an open fire... :-) These experiences and memories were unique and irrecoverable, but at least I have my telly!

The first modification I did for this console was to connect an adapter to it. Those huge batteries were turning out to be expensive, and since this console is not a portable, I figured connecting an adapter would save me money. With the latest advances in power supplies, adapters are getting ever smaller, and I managed to find a very small adapter originally used as a mobile phone charger. It provides 6 V at 300 mA, which is just enough to power the console.

I was getting tired of people tripping over the cable and the jack plug had become loose, so I decided to install the adapter circuit within the console, and have a nice thick mains cable running to the wall socket. This is of course so much nicer than having a large adapter dangling at the end of a thin wire. I also installed a UHF socket, and now use a fly lead to connect it to the telly. I did not like the idea of all the wires dangling off the console, and it is so much more civilised now. Perhaps one day into the far future someone will come along and say that it would be so much nicer to have a fusion power pack installed. :-) Of course, Larry Page is working on this as I write this. :-)