I do like vintage arcade games, i love their simplicity, how a picture can be built up purely by using mundane logic gates in the right combinations. Back in the day when these things were new, it was enough of a wow factor just to have something that you could play and control - moving about on a TV screen, of which the vast majority were black and white. It was natural therefore that videogames were not born into a colour world, for many reasons including reducing complexity but more importantly for the cost factor of the monitors. In 1972, colour TV sets and monitors were prohibitively expensive, and the coin-operated industry was driven by the bottom line, there wasn't room for being fancy at this early stage, that was to happen in waves of prosperity later on through videogame history.

So, you can't get more simple than the game of PONG, but i always thought about how it might have looked, or may have been developed should colour TV's and monitors have been much more commonplace.

Nearly 40 years after its inception i decided to see how easy and effective adding colour to the game of PONG might be.

So - first i need to find a suitable game PCB to have my wicked way with...

PONG clone pcbs are fairly common, and don't get any love amongst collectors. I have a whole bunch of them that i have acquired along the way. I looked through what I had and settled on the one shown opposite, its a Chicago Coin 'TV Tennis'.

I've had this pcb for a long time, only partially tested. I decided that nobody is ever going to want it as it is.

Firstly, this pcb is a lot like PONG but is for 2 or 4 players. The pcb is not however based on Pong Doubles from Atari, its just an extension of a regular Pong pcb with a few more chips for the extra paddles and changing some 3-input gates to 4 inputs to cope with the extra logic needed.

This could be a unique redesign by Chicago Coin, but I have subsequently found out that it directly matches Midway's 1973 game 'Winner IV'. (I have a Winner IV pcb and its identical). The chips on this pcb date from mid 1973, and Winner IV is marked as coming out in October '73 so maybe Midway cloned this design. I don't know for sure.

Sadly, I can't currently find any schematics for Winner IV, so for following the technical part below, you will have to refer to the 'Pong' schematics (found here) and just get the gist of it, they're very similar but not identical of course, most things match up.

I have several aims for this pcb:
A) make this 2 player (PONG STYLE) or 4 player (PONG DOUBLES) style 
Solution to A) I have found that holding the 'serve' button in and then coining the game will actually start a 2 player only game, so for now thats this sortof answered at least.

B) Make the sound work like pong, driving a speaker directly
I found a cap and a resistor near A2, hooked to the TTL chip sound output, I simply removed this and wired it direct to the speaker, and I got sound...

C) Make the game in output in nice RGB colour so it can be played on a JAMMA setup.

D) Add the game features described by Atari as 'Super Pong' 

E) Convert the coin and start buttons from N.C/N.O to regular active low inputs.

C) this ones the biggie...

The screenshot mockup opposite is my idea of what I want the game screen to look like, I asked friends online about which direction to go in, and this was about the 8th iteration of trying different colours in different places. I think it definitely spruces it up, while in both 2 player and 4 player mode, provides enough contrast where it matters to make the game still playable.

Now, in order to achieve this, this means grabbing each element of the game as it is made up in TTL and combining it with the relevant RGB signals in the right combination to achieve the colours we want.

So, in order to achieve this, we need to define how we build up this picture above... I came up with a rough diagram , writing the elements on one side, colours on the other and drawing it like a circuit, finding out what needed to be connected to what.

PADDLE numbers are taken from left to right in the screenshot.

From this diagram above, it makes it easier to see what needs to be connected where.

RED:
NET/BOUNDARIES
BALL
PADDLE 1
PADDLE 3

So lets start with the NET and the BOUNDARY (the net is the dashed line in the middle, and the boundary is the line that masks the top and bottom of the screen) We want these to both be white.

Currently when we look at the schematics there are 3 elements combined to create the composite video output, found at area D3/2 on the Pong schematics. VIDEO, SYNC and SCORE are combined through resistors. This already tells us that the SCORE is separate from the VIDEO. However, when you look at this with the video probe, you can see that the SCORE also includes the boundaries. Since we want the score to be green and the boundaries to be white we need to separate these two.

Since we want the NET and the Boundaries to be white we now need to combine them into one signal that we can squirt out to each colour...

The 7400 (quad NAND gate) is numbered zero zero for a reason, its a building block that can be used to create all other known logic gates. As such we can do both operations needed for combining the two signals properly without using two flavours of IC's (the 7404 and 7402).

Firstly, the inverter, this is essentially a NOT gate... We can make this out of one stage of the 7400...

We need to invert (NOT) the BOUNDARY signal

And then we need to OR the resulting signal with NET : This way we'll end up with a useable signal that is positive going like all the rest.

Now its time to power it back up... and we get.....

 

Success!!

Which I think you'll admit, looks pretty close to what I had intended!!! My monitor quite often misses the top few scanlines of a video signal, so the top line is not shown in the photo, but trust me, its actually there :)

And of course, in the classic 2-player regular PONG mode opposite :