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1973 - TV Tennis (PONG) pcb plays in colour!

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P-Man View Drop Down
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    Posted: 16 Feb 2011 at 8:14pm
hi all.

I have made a dedicated page on my website with much more circuit/diagram detail available :
http://www.andysarcade.net/personal/bronzeage/tvtennis/

original post:

 So i've had this pcb for a long time, only partially tested. I decided that nobody is ever going to want it, so i decided to try out something i've been meaning to do for ages... convert a dull black and white game to COLOUR!! So, bring on the bling.

 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.

UPDATE 17/02/11 - I've worked out that this is actually a PCB copy of Midways game 'Winner IV'  so if you can find the schematics for that (I can't) then the pcb matches it.

Here is what it looks like right now :



I have several aims for this pcb:

A) make this 2 player (PONG STYLE) or 4 player (PONG DOUBLES) style
B) Make the sound work like pong, driving a speaker directly
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.

here we go:

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 A sortof answered at least.

B) found a cap an a resistor on the TTL chip output, i simply removed this and wired direct, and i got sound...

C) this ones a bit long...

Here are my ideas of what I want the game screen to look like :

http://www.andysarcade.net/pix/mockup7.jpg

 I think this will make the game a bit more lively looking. Now, in order to achieve this, this means grabbing each element of the game as it is made up in TTL and combinging it with the relevant RGB signals in the right combination to achieve the colours we want.

 You can follow the progress below by looking at the Atari PONG schematics found here:
http://arcarc.xmission.com/PDF_Arcade_Manuals_and_Schematics/Pong%20Schematics.pdf
This pcb is basically the same, and you should get the idea from following the details below and referring to the schematics.

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



Then i wrote down what went into making up each colour...

RED:
^^^^
NET/BOUNDARIES
BALL
PADDLE 1
PADDLE 3

GREEN:
^^^^^^
SCORES
NET/BOUNDARY
BALL
PADDLE 2

BLUE:
^^^^^
PADDLE 2
NET/BOUNDARY
PADDLE 4
PADDLE 3

In combination of course, NET/BOUNDARY goes to all 3 colours and makes white. The BALL goes to just red and green, this makes yellow, PADDLE 2 goes to green and blue, making cyan... and so on and so on...

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...

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 seperate 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 grean and the boundaries to be white we need to seperate these two. 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.

 Now, we want the boundary and the net to be the same colour, white. In order to do this, we need to combine both signals before sending out to all three colours. We only have 4 inputs per colour available so it makes economic sense to combine two signals that will be colours the same now, rather than passing tem through seperately. 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,hwoever thats getting a bit ugly.

 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...

SEE THIS LINK: http://en.wikipedia.org/wiki/NAND_logic

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.

 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 detatched 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!

 So, in order to make our wonderful game RGB, i need to combine various signals in their respective combinations to ech RGB channel. The proper way to do this is to use some more logic. Now, seeing as we are no longer using the composite video signal, i can use the 7425 @ F2 and its inverter at E4 to drive our RED signal. This was previously used to combine NET, BALL and both PADDLES together into the black and white signal. Pin 12 of E4 is our final output, run this through a 33ohm resistor to the edge conector and run that to the RED input to your monitor.

 Now we have our NET/BOUNDARY signal, we should snip input pin 10 of F2 and lift it, wire the boundary signal here.  We now need the BALL, as luck would have it, this is already wired to pin 13 of F2! (this is why i chose to re-use this gate :) We now need to hunt out PADDLE 1, this is available from D10 pin 11. We snip the leg input to F2 pin 12 and wire this to PADDLE 1. We then find PADDLE 3, this comes from E9 pin 6. We isolate pin 9 from F2 and wire this to E9 pin 6. Et Voila, we now have the RED colour channel wired up and ready to go!

 Now we need to build the GREEN and BLUE colour output. We are going to have to use another 7425 (Dual 4-input positive-NOR gates with strobe). So i've bent out all the legs and piggybacked this IC onto a ceramic TTL chip @ C3. We can ignore the 'strobe' input on this chip, well not exactly ignore, but we wont be using its functionality, so we have to tie it high, we do this by joining pin 11 to 14 and 3, this ties both strobes high. 

 So, looking at our table, we want to add the scores, net/boundary, ball and paddle 2 to it. We can get Net/boundary from pin 8 of the piggybacked chip @ D1, so we hook that to pin 13. We can grab the SCORES from pin 8 of D3, we'll put that on pin 12. Now we need to find BALL, this is from G1 pin 4. Paddle 2 is from D10 pin 12, we wire that to pin 9, and thats the GREEN signal all wired up!

 Now for the remaining colour, BLUE, we need to add Net/boundary, paddle 2, 3 and 4. Because we've wired a few of these to the same chip already this should be fairly straightforward. For net/boundary we wire pin 13 to pin 1, for paddle 2 we'll wire pin 9 to pin 5. For paddles 3 and 4 we can cheat a bit and grab the combined paddle signal from F3 pin 1, this one signal contains both PADDLE 3/4 signals... so, we need to tie the remaining input LOW to disable it on the 7425, so we wire pin 4 to 7... and thats Blue done!


 Now we have built the 7425 arrangement, its output is the inverse of what we need. Fortunately there are some unused gates on this pcb, by looking at all the 7404's on the pcb i can see that C1 pins 8/9/10/11 are not connected to anything, and so is E4 pins 8+9. To keep it tidy, we can use the chip at C1 for our final output inversions. We connect a 33ohm resistor to pin 8 and run the other end of the resistor to the edge connector, which is in turn connected to our GREEN video signal. We wire pin 10 of C1 through another 33ohm resistor to the edge connctor, this gives us our BLUE video signal.


 And thats it!!

when we fire it up, we get :

which i think you'll admit, doesn't look a million miles away from what i intended!!!

My monitor quite often misses thetop few scanlines of a video signal, so the top line is not shown, but trust me, its actually there :)

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


here is a large photo of the pcb as it is modded now :
http://www.andysarcade.net/pix/DSC_0201.JPG

now to do Step D and E... but i'll leave those for another post, i'm tired out and done for the day...

B/W games can be fun, if you mercilessly hack them kicking and screaming in to the 80's by making them output in Colour :)



Edited by P-Man - 19 Feb 2011 at 10:37am
Andrew Welburn www.andys-arcade.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darthbob1425 Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2011 at 8:36pm
Frickin' geniusClap I want one
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DanP Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2011 at 9:28pm
Great writeup Pman, fantastic to see something that old given a new lease of life.   Look forward to playing it one day!

Dan
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Post Options Post Options   Thanks (0) Thanks(0)   Quote g00n3r Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2011 at 10:19am
Clever chap, I reckon if you work hard at this then one day you'll have your own business doing pcb repairs etc. Thumbs Up
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote P-Man Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2011 at 5:13pm
I decided to put up a page dedicated to this mod, and spice it up a bit.

http://www.andysarcade.net/personal/bronzeage/tvtennis/
Andrew Welburn www.andys-arcade.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paulcan69 Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2011 at 11:49pm
Amazing!
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