erratic Trakball movement

[Grand_National]

Hi!

 

Since I have the 800XL working again, I thought I'd play one of the classics.  I found my old copy of Missile Command (cart - no drives working yet) and found a few Trakballs.

I understand Control-T before hitting Start should put the game into 'Trakball mode'.

When doing so, the screen flashed and I thought I was ready to go.

 

The Trakball movement was awful.  This Trakball was barely used and wasn't really stored in a damp area, but it barely would roll without getting bound up.

After reading some posts and a watching a video, I disassembled (this unit never disassembled before) and gave each mechanical (not electrical) moving part a (very small) drop of 3-in-1 oil.

The ball rolls freely once again, since there is very little wear on this unit.

 

The problem still is the cursor in the game moves completely erradically.

I literally have NO control.

 

I checked the switch on the back of the Trakball and it is in TB mode.

I tried JS mode and restarted the game, but I get the same behavior.

 

Its not like only some directions move and other don't.  Its completely erratic. 

Sometimes the cursor will "fly" across the screen and other times it "jumps" in bursts, but usually it gets stuck on one side or the other and never really moves up or down.

The fire buttons are fine.

 

I've found a few posts of BASIC programs which supposedly will test the output.

I'm not sure what else to look for b/c as I said, this unit is "almost" brand new (based on usage)...bad electronics in the Trakball, bad game port (I tried both), or something with the 800XL?

 

All comments, ideas, etc. are welcome.

Thanks

 

[Rybags]

The trakball in native mode just outputs grey codes for the X/Y axes like an ST mouse.

It's pretty unlikely the computer would have a problem - the bit pairs just come across the same as joystick input (though somewhat faster).  It's up to software on the host to interpret the bit changes and determine direction/velocity.

 

If the mechanism is experiencing jitter then you'll likely end up with what you're getting.  I've not pulled down an Atari trakball so don't know what to look for - not sure if they're electromechanical or optomechanical - the optical types of mechs tended to be more reliable.

 

You might try pulling it apart, take the ball out and operate the rollers direct by hand and see what results you get.

[gilsaluki]

Most likely needs a good cleaning of the rollers and ball.  Easy to do. 

[Grand_National]

Thanks.

The pickups are optical AFAICT.

I already have thoroughly cleaned everything and the ball rolls very nicely, but I still have the same result.

I guess the next step is to connect it with the Trakball open and move the "optical cut-out" wheels manually to see if the cursor moves and determine if the ball is slipping and not moving the rollers which the optical wheel is attached to.  As for the slippage possibility, I'm very doubtful though b/c I can hardly get any vertical movement (when it does move it just goes all the way to the top or bottom w/o any ball movement and also has similarly completely random horizontal movement.  I would think that if the ball was slipping intermittently, the cursor would "jump" according to the direction the ball was being rolled, but it doesn't.  Seemingly random.

 

[+DrVenkman]

You might have a bad logic chip. Download the CX-22 Field Service Manual - it has a schematic and troubleshooting steps.

 

 

[Grand_National]

I dug through my boxes of Atari stuff which I haven't touched in 32 years.  I forgot half of the stuff I had.  A regular joystick works with Missile Command.  I found a CX22 trakball.  A little 3-in-1 oil and its working fine in trakball mode.  I found another CX-80.  That works fine as well.  The first CX-80 though does not.  I have virtually no vertical movement and erratic (completely random) horizontal movement.  The two PCBs seem to be soldered together, so I can't swap boards to narrow it down.  I looked at the schematics (thanks Dr. Venkman), but I'm struggling to narrow it down.

[BIGHMW]

I am a proud owner of a NOS 65XE I picked up on eBay a few weeks ago and also a CX80 I also ordered NOS 15 years ago and my Ultimate Cart will be coming in later this afternoon and I will have many of my thousands of .xex files from various sources including Homesoft loaded on an SD card on her including Missile Command and Centipede (both the original 8-bit and 5200-to-8-bit conversion as done by Glenn The 5200 Man), and Millipede and am looking forward to playing them on it, is there anything I should be aware on the operation of it besides utilizing the TB/Joystick switch whenever necessary for each specific game???

[Grand_National]

I've checked the continuity of the cable, all of the PCB solder points on the PCB to ground, the TB/JS switch, and made sure no other cable edge connections are grounded.

I did notice something strange tho.

It would seem as though there was some rubbing or scraping on 2 areas of the PCB over top of traces.  One area is where a plastic support sits.  These traces seem to have been repaired (with solder). (Some of the scraping is from me trying to determine if the traces were cut, so ignore that.).

Sorry, its very hard to get good pics, but the solder "lump" is very obvious using a magnifying glass.

To the best of my knowledge, this trakball has never been opened (prior to me the other day).

I checked continuity across all of the traces and they all seem good so that's not the erratic behavior of the unit.

The solder traces though raise an eyebrow.  Anyone ever see this?

Also, no one has ever found a CS80 Field Service Manual right, because the PCB is very different from a CS22

Thanks

 

[+Nezgar]

I've heard some CX80's operate in a mode compatible with an ST mouse, which is slightly different than the CX22... So may not work with Missile command... i thought that was a mod though done by people hoping to use them on ST's, not out of the factory...

[Grand_National]

Yes, I've seen those posts about mod'ing them.  All of the traces look factory and there are no extra wires or evidence of wires having been soldered on at any point.  The one area with "7 traces" looks like a scrape/scratch.  I'm fairly certain that the other "parallel scrape of 4 traces" area is a rub from one of the plastic case supports. The PINPOINT soldering looks like a repair but by a soldering tool smaller than any tool I've ever seen. 

 

The CX22 FSM is only somewhat helpful. I'm looking for a "symptom / possible cause" section for the CX80 like the CX22 FSM has for it.  

 

Dr Venkman suggested a bad logic chip. Are the logic chips a available?

[+DrVenkman]

15 minutes ago, Grand_National said:

Dr Venkman suggested a bad logic chip. Are the logic chips a available?

I’ve never taken apart a CX-80 but the chips in a CX-22 and the ones inside a 5200 Trak-Ball certainly are. They’re just standard TTL logic chips.

[Grand_National]

Forgive for asking this but the FSM lists a 4019B and I found a HEF4019BP - aren't the first few letters the manufacturer and any trailing letters the packaging type and temperature range?  So these would work?

[+DrVenkman]

So long as the package style is correct DIP, correct number of pins, they should be interchangeable. You can look at the datasheet from the manufacturer to confirm, but 4000-series and 74-series logic has been in regular continuous use for decades. Modern-made versions in the same form-factor are generally fully-compatible with vintage devices. 

[Grand_National]

I've gone over all of the traces again and everything seems fine as well as testing the cable again.  In TB mode, with the case apart, by spinning the axles manually, I've determined I can only go down and left.  Occasionally, it may jitter to the right or up ever so slightly, but ultimately, the cursor always ends up in the lower left every time.  In JS mode, just as the game intro starts, I can briefly go right, but then when the game actually starts, only left and there is no vertical movement at all. 

 

Looks like I'll be ordering those chips.  The main PCB is held in place by the optical sensor wiring and the TB/JS switch.  Once I figure out how to unclip those plastic tabs w/o breaking them, I'll be in business.  Thx

[Grand_National]

I'd like to ask one more question because I've seen this on several threads.  People use the term, "CX-80 acting like a CX-22".  My CX-22 has a JS/TB switch just like my CX-80s, so I'd think the functionality of both models would be the same in both modes.  What does "acting like a CX-22" really mean?  What are the functional differences? or are they referring to the model which doesn't have the switch and I assume only works like a JS?

 

[+DrVenkman]

28 minutes ago, Grand_National said:

What does "acting like a CX-22" really mean?  What are the functional differences? or are they referring to the model which doesn't have the switch and I assume only works like a JS?

Read this thread. Questions like yours are crucial to the talented home-brew authors who’ve been creating amazing Trak-Ball games for the 2600.  

[slaanesh]

@Grand_National Just wondering if changing the ICs fixed the issue?