CV Roller Controller: Part 2.

[CV Gus]

A while back, I started a thread about the problems I was having with my CV Roller Controller:

 

http://www.atariage.com/forums/index.php?showtopic=129538

 

 

In short, whenever it was in the "Joystick" position, it always acted as if you were holding the regular controller to the left or right (spinning the trak-ball would determine which way). Also, whatever you did with one controller would affect BOTH players- as if you had it in the "Roller" position.

 

But when in the Roller position, the trak-ball worked fine, and so did the regular controllers. In short, you couldn't play joystick games with the trak-ball (yes, you actually could- it was in the commercials and the instructions).

 

 

Well, I located a "regular" schematic about the controller. All I had to use was a beat-up old multitester. I set it on "DC Voltage" mode.

 

http://xi6.com/hacks/rollctl.gif

 

 

Much to my amazement...I actually found the problem.

 

It involves chip U-4. There's a "gate" that is supposed to have a "low" output when the trak-ball is NOT being spun to the left or the right, because you have a Low and High inputs. Only with a High and High (it's an "AND" gate) are you supposed to have a High output. In other words:

 

L+L=L

 

L+H=L

 

H+H=H

 

These refer to voltages. If you look at the "Joy/Roller" switch, you'll notice that when it's in the Joystick position, that lead running to U-4 would be High. Thus, when the roller is spun and a High signal is generated, you get H+H=H.

 

But that point, pin 11 on U-4, was ALWAYS High. This was it: it connects to the horizontal outputs. It fooled the CV into thinking the ball was always being rolled.

 

Since Radio Shack is no longer what it was, getting a replacement chip around here is out of the question. I'd have to order it, except- see that "SPARE" part of the U-4 chip?

 

That's right- I disconnected the 3 pins on 11, 12, and 13, and wired in 4, 5, and 6.

 

Same kind of gate.

 

Now, that part works fine!

 

Of course, there's still that odd fact that it has to be in "Roller" mode to properly play a 2-player joystick game, but that's probably something on the switch. If so, I'll get to it later; if not, I won't bother, because it functions just fine.

 

To make it a bit easier, I built (out of junk) a simple logic probe. It's the 2-lead kind. But I tried (after unplugging the CV) to touch just ONE battery lead to a "NAND" gate, and sure enough saw it light up! Therefore, if I can get a $1.50 chip, I can build a ONE-lead logic probe. It has to have a NAND gate on it somewhere.

 

This was my first repair of this nature.

 

[sidcrazy]

That's amazing Gus. I wish I could do repairs.

[CV Gus]

I can also now properly play Defender.

 

Someone mentioned being unable to do so- try playing it on Joystick mode, then Roller. See if that helps.