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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.
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Here is what the game screen looks like currently. BORING black and white.. lets bling it up! |
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I have several aims for this pcb:
A) make this 2 player (PONG STYLE) or 4 player (PONG DOUBLES) styleÂ
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'Â
E) Convert the coin and start buttons from N.C/N.O to regular active low inputs.
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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.
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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.
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From this diagram above, it makes it easier to see what needs to be connected where.
RED:
NET/BOUNDARIES
BALL
PADDLE 1
PADDLE 3
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GREEN
SCORES
NET/BOUNDARYÂ
BALLÂ
PADDLE 2
BLUE
NET/BOUNDARY
PADDLE 2
PADDLE 4Â
PADDLE 3 |
In combination of course, NET/BOUNDARY goes to all 3 colours and makes white. The BALLgoes to just red and green, this makes yellow, PADDLE 2 goes to green and blue making cyan... and so on and so on...Â
You can see quite neatly this means we have 4 elements for each channel of colour to combine. This will be quite crucial a bit later on... |
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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.
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| Area B4 on the schems shows the 7430 combining all elements of the score, look at pin 1, it is tied high on PONG, but on TV tennis, this signal is a square wave at the beginning and end of the video raster that gives the bars top and bottom and gets mixed in here. So, in order to isolate this, we snip pin 1 of D3, we have now stopped the boundary from being combined with the SCORE signal. |
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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...
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We only have 4 inputs per colour available so it makes economic sense to combine two signals that will be coloured the same, rather than passing them through separately. The boundary signal is currently negative in relation to the NET signal (the 7430 would have inverted its output when it created the SCORE signal). NET is generated at F1 pin 8 on this pcb. We could use a 7404 to invert the signal and a 7402 to combine the signals, however thats getting a bit ugly. |
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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).
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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.
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So, I piggybacked a 7400 over another chip on the pcb (at D1), connecting the Vcc and Gnd to the IC below it. All pins are lifted clear and cut short. Pins 1 and 2 are joined together and connected to the BOUNDARY signal that we detached from D3 pin 1.
Pin 3 on our piggybacked 7400 is now our inverted boundary signal that we now want to pass into one half of an OR gate, so we solder pin 3 to pin 4 and 5, Pin 6 is wired to pin 9 for now. Now we grab the NET signal from the snipped leg of F1 pin 8 and put that onto pins 12+13, we then solder pin 11 to 10. The resulting output from pin 9 of the 7400 is now a combined NET+Boundary signal! |
