Need Electronic Wiz to design adapter for Asteroids

[fredster]

I know there are lots of electonic wizards here that could solve this problem I have in a heartbeat.

I have an asteroids deluxe and an asteroids.  I want to put the asteroids in the deluxe.

However, the deluxe is mirrored.  The game is reversed on the X.

They make a rom hack and you can reverse the wires on the Monitor to play.

But what I wanted was a voltage inverter that changes the +5/-5 voltage to inverse.  That would reverse the X image on the screen.

I can build the circuit, but I'm not much into designing the circuit.

I'd just put the circuit on the adapter.  That way I don't have to hack anything, the adapter does all the work.

Any takers?

[CheffoJeffo]

I was just about to suggest that you go to RGVAC since I read a request similar to yours only yesterday ... then I checked the post ...

I would be interested to see what people come up with.

Cheers.

[fredster]

Yeah, me too.

They make a jamma centipede adapter. I bought one, I think from two bit score?

Something like that.

I have that TL081 chip, but I can't design the circuit.

[JCL]

Gain of 1 inverting buffer. Simple op amp circuit.

Here's a page with a simple picture and the simple math:

http://ourworld.compuserve.com/homepages/Bill_Bowden/opamp.htm

Pick RA and RB to approximate the impedence of the original driver. If you don't know, start with 10K resistors and see if it works. If not go lower, but I wouldn't go below a k ohm. If you need to go lower than that, you really need to be sure that you aren't going to burn out the driver of this voltage.

 At video frequencies, probably nearly any opamp will do, including the TL081 you have. Power it with + and - 12 volts.

Do neat point to point soldering, keep leads short, etc on a piece of perf board. Get it working and if it is noisy or unstable tweak it.

[fredster]

Thanks JCL,

I have only 5V DC and 36VAC to work with.

I'm not into the design.

[ChadTower]

Can't help, but I am reading the topic intently.

[2600]

How good is your soldering and how do you feel about a small modification to your Asteroids board?

Instead of building a circuit that may introduce noise, DC offset, Incorrect Gain, etc you could adjust the X on the Asteroids board.

Not sure if all asteroids PCBs have the same video output circuit, but the manual where you got that pic from it looks like if you lifted pins 12(NINV) and 13(INV) of D12 and swapped where they went to with some jumper wire you would solve your problem.

Let me know if you need more info.

Link to manual I was looking at:
http://www.arcadedocs.com/vidmanuals/A/Asteroids-sp.pdf


Edit: Forgot to say pins to which part, D12

[fredster]

I can solder chips into boards with a cheap soldering gun and feel absolutely unbeatable.

However, I want NO hacking on the board. None. It want to be able to take the asteroids board from any asteroids machine, fit it with the adapter, put it into the AD and play like it's a standup.

The Monitor will reverse if the voltages are reversed. All I need to do is reverse the X output voltage. 

I've read the manual over and over. I know the pinouts. I'm a remove and replace guy.

What I want to do is use the poor man's asteroids adapter here -
http://www.brasington.org/arcade/tech/astdlx/ and add a hole at Pin 17.
 I figure I'd drill a hole through Pin 17.

Then I need to tap the power at pin 1 and 2 for +5v to power some type
of circuit. The circuit could be simple using some transistors or even
a TL081 (ECG 857M).  I'd mount a little perf board circuit on top of
the adapter with these inputs.  Then I'd take the Output of this
circuit and put it back on Pin 17 and U.  It would all fit right on the
blue piece of the adapter and take up like no room.


It would reverse the X voltages and therefore reverse the monitor
picture in X. That's the concept anyway. This way I don't have to hack
into any board or monitor.

Here's the pinout of the asteroids board.


          _______
               GND | 1| A| GND
               +5V | 2| B| +5V
                   | 3| C|
    Counter Center | 4| D| Counter Left
           Audio 1 | 5| E| Audio 2
       Start 2 LED | 6| F| Counter Right
          Player 2 | 7| H|
       Start 1 LED | 8| J| Player 1
              Slam | 9| K| Diagnostic Step
        Hyperspace |10| L| Self Test
             Z GND |11| M| Z Out
       Coin Center |12| N| Start 1
         Coin Left |13| P| Start 2
            Thrust |14| R| Coin Right
      Rotate Right |15| S| Rotate Left
                   |16| T| Fire
             X Out |17| U| X GND
             Y Out |18| V| Y GND
          Invert X |19| W| Reset
            36 VAC |20| X| 36 VAC
           + Sense |21| Y| +5V
           - Sense |22| Z| GND
                   -------       
       

[JCL]

That's a cute circuit. I'm assuming it provides voltages to the video output drivers at either +/- 8.2 volts depending on the inversion. Of course, to turn something upside down requires and X AND Y inversion. You just want X.

There's two ways of dealing with it then. You could (if you were brave, foolish, or more experienced) modify your asteroid board to use the existing voltages from the inverter circuit to just invert X and not Y. You would need to cut a trace and then solder a wire from another place to the trace you cut.

I think your method of using an add on board to just invert X is probably a little easier and certainly safer.

However, inversion of a DC biased circuit does require a + and - voltage. I think you may actually have reasonable voltages available if you are able to tap the voltages off your board. But this may be more than you want to do. The other option is to add a power supply that has + and - 12 volts. A regulated wall wart with these voltages would do. A computer power supply also provides these voltages. If you use a PC power supply, you need to provide a dummy load on one of the lines. A quick google search will show how to do this.

However, as a really quick and dirty experiment, you could even use 2 9 volt batteries to create + and - nine volts to see if this circuit does what you need.

I'm going to draw a schematic with what I would try if I were you. Wire and solder it up on a perfboard as described in these links:

http://www.dartmouth.edu/~sullivan/prototyping.pdf
http://www.geofex.com/Article_Folders/protostyles/proto_styles.htm
 
Power it with +/- 12 volts if you can, but anything more than around + and - 8 volts should work.

Check voltages with a DVM, checking waveforms with an O-scope would ideal, but as long as you only drive the circuit with fairly low voltages (+/- 12v for example), you shouldn't be able to damage anything even if you messed up.

[fredster]

That's the inversion circuit on the board for cocktail.  I'm not quite sure how it works at the output, or where it goes from Pin 19.

People have done this two ways.  One way was to actually reverse the wires on the monitor yoke to reverse the direction.  The other way is to just put a patched rom in the board.

I guess I could do the patched rom, that's the easiest.

But my vision is to just play my Asteroids Deluxe cab, then put in this board that's just a stock unmodified Asteroids board.  Fit it with the adapter between the harness and the board and play asteroids like it's in an asteroids cabinet.  The adapter would mirror the X for me somehow by actually reversing the AC off the board output.

No Machine or Board Hacks at all. Nothing.

Like they do with centipede.  There's a jamma adapter available that has a sound amp built in - http://www.arcadeshop.com/pics/centipede-jamma-adapter.jpg

But I only have the harness to power the circuit. It only has +5vdc  and 36v AC

(see the above pinout)

[RayB]

Could the patched rom be piggy-backed on the original rom and have a switch to alternate?

[fredster]

No, stock board, adapter.

It's easy to just put a rom in.  But I might want to sell the board or get another board or whatever.

I don't think anybody has done this before.  They just did the cheesy adapter or the rom hack.

I think swapping the monitor wires is pretty lame.

I want the only thing working differently than it should is the adapter.
It does all the work.

[JCL]

If swapping the monitor wires works, why not do it?

I assumed that swapping the wires wouldn't work because one of them was tied to ground. But if it works, why avoid it?

[2600]

I don't think swapping the monitor wires will work, single-ended signal, and may damage the board.

My suggestion basically made it so that the X thinks it is in cocktail mode and is a pretty minor board modification.

You can go with the inverting amplifier and use a DC-DC converter to get the 12 and -12 volts.  Put some caps and an inductor on there to clean the power.

[fredster]

The RGVAC guys are telling me I'm screwed.

I'll go for the rom hadk.  I contacted a guy at www.hobbyroms.com.  Apparently he can make the chip that reverses the signal onboard. 

I'll settle for that I guess.  I just thought we could find some way to figure it out.