Heavy Sixer | TRAK-BALL problem

[Klemen]

Hey everyone,

 

I just received a new (old) CX-22 TRAK-BALL in the mail. The unit has never been used before and works as expected in Joystick mode. But, when I set it to TB mode, the controller appears to be malfunctioning. The pointer in TB mode is only able to move down and to the right, and even that is very sporadic and unpredictable.

 

Has anyone had this issue before where Joystick mode works perfectly fine but the TB mode does not? The ROMs I've been trying TB mode on were downloaded from here (I have made sure to use the correct CX-22 NTSC ROM files, so software shouldn't be the problem). I have also tried the detection software linked in that thread and it detects the CX-22 as it should.

 

Could this issue be related to my paddle problem? I'm starting to suspect the issue is with my Heavy Sixer unit itself, not the controllers. If anyone has any steps for me to troubleshoot or have any other ideas on how to get this working I'd be very thankful.

 

[fiddlepaddle]

The obvious: try another console unit. Follow/trace the signals on the connector and check continuity on everything you can.

[Omegamatrix]

Try a few different games. Try Missile Command and Star Wars and see if they behave the same.

 

Also, for Star Wars make sure there is no AtariVox in the right controller port.

[Klemen]

10 hours ago, fiddlepaddle said:

The obvious: try another console unit.

Not an easy thing to do, unfortunately. I'm in Europe where Atari consoles aren't as easy to come by and I don't know anyone who owns one.

 

9 hours ago, Omegamatrix said:

Try a few different games. Try Missile Command and Star Wars and see if they behave the same.

The behaviour is consistent across all games found in the thread I've linked. I don't have anything else plugged in (and my console isn't modded in any way).

[alex_79]

21 hours ago, Klemen said:

Could this issue be related to my paddle problem?

I don't think that's related. Paddle pots and trak-ball directions uses different pins which are connected to different ICs.

 

It might be a faulty IC inside the trak-ball itself.

 

Could you try the test rom posted here?

There are 4 yellow squares on the bottom left of the image, which show the status of the 4 input pins used for the directions.

On a working trak-ball, if you slowly move the ball you should observe the following behavior:

 

the 1st square pulses on and off when moving in the VERTICAL axis

the 2nd square is constantly OFF if you're moving UP, and constantly ON if moving DOWN

the 3rd square pulses when moving in the HORIZONTAL axis

the 4th square is ON when moving RIGHT and OFF when moving LEFT.

 

 

 

[alex_79]

I had a look at the cx22 schematic, and I think the issue might just be contact oxidation in the joystick/trak-ball switch itself (which is likely if the switch has not been operated for decades).

 

 

The mode selection circuit uses a CD4019B (quad AND/OR select gate).
The control pins Ka and Kb are pulled high through 10k resistors, and the switch grounds one or the other to pass the joystick (R,L,D,U) or trak-ball (Y_ck,Y_dir,X_ck,Y_dir) signals to the 9 pin plug.

 

 

What I think might be happening here is that the switch doesn't make contact when in Trak-ball mode and thus fails to ground the "K_a" pin as it should.

According to the CD4019B datasheet, if both control pins are high, the output will be a logical OR of the inputs.

The result would be that the trackball would only move down and to the right.
In fact, in "up" and "left" directions, the R and D joystick signals are HIGH and the result of the OR operation with the two axis clocks X_ck and Y_ck would be always a HIGH logic level. Which means that the clocks aren't passed to the console and therefore there isn't movement of the cursor.
Additionally, this behavior would only be reliable above a certain speed, as if you spin the ball slowly, the joystick directions become a series of pulses instead of continuous signals (this would explain the "very sporadic and unpredictable" response described by the OP).

 

Proposed solution:

Try toggling the switch back and forth several times, in the hopes that this "scrubs" the oxidation out of the contacts and restore functionality.
Sprying contact cleaner inside the switch it might help too, if possible.

 

Edited August 30, 2020 by alex_79

[+DrVenkman]

If it's merely corrosion on the switch, spraying electrical contact cleaner, especially a really good one like Deoxit D5, would do a lot more than simply cycling the switch.

 

However, with a wonky system, if that DOESN'T fix the issue, it's hard to know what to do next. I mean, the system already doesn't read paddles - there are bypass capacitors on the signal lines that might be shorted to ground, which could cause that problem, but it might also be a bad TIA chip. If the TIA itself has a problem, however, there might be other problems that interfere with an accurate test. So the best thing would be to find a second, working system to help determine if the problem is with the Trak-Ball or the console.

 

My personal guess - based on a similar issue I encountered with the 5200 Trak-Ball - is that one of the 4000-series CMOS chips in the Trak-Ball is damaged. These chips are susceptible to damage created by static discharge, even just the usual build-up in a carpeted house in cold, dry weather. 

 

[Klemen]

On 8/30/2020 at 12:07 PM, alex_79 said:

Proposed solution:

Try toggling the switch back and forth several times, in the hopes that this "scrubs" the oxidation out of the contacts and restore functionality.
Sprying contact cleaner inside the switch it might help too, if possible.

I opened up the Trak-Ball today and gave the toggle switch a good spray with the contact cleaner. It turns out you were completely correct - that immediately fixed the issue and the Trak-Ball performs perfectly. The bad news is that I can't stop playing Missile Command TB now

 

Thank you so much @alex_79!