Two Issues with 1200XL

[800_Rocks]

I picked up a new to me 1200XL today. I knew from the seller that no keys work so I watched a couple videos on fixing the Mylar connection. The 1200XL otherwise looks great but I noticed two other issues when I was testing tonight. This is my first 1200XL so I’m not sure these next two issues are common or not and what I might troubleshoot for these:

 

1) no Power light

2) some odd joystick behavior but only in PacMan. It’s as if the joystick is stuck in the due South position.  However, the same joystick performs flawlessly in DonkeyKong. Any relation to the assumed bad Mylar?
 

Things that work:

- BASIC boots from cartridge, shows the ‘Ready’ prompt

- Star Raiders boots from cart (the initial star field start screen) however without the keyboard that is as far as I can get

- as mentioned above, Donkey Kong works great, joystick works, sound, great video quality, etc. 

- booted DOS from SD-Max

 

[Sugarland]

That is an epically beautiful machine! Congrats!

 

There is a secondary connector (grey cable) for the keyboard iirc. Five pin connector in the front left of the motherboard. Did you reconnect it correctly?  IIRC that cable is for the lights.  The joystick in Pac-Man may not work because of the 1200XL's known incompatibilities. Try an emulator with the 1200XL OS and Pac-Man to see if you can replicate the joystick compatibility issue. 

 

If you wan to to use the machine as your primary A8, then it is recommended to upgrade the OS to either OSB or an XL/XE OS. XL/XE is preferred but will need an MMU chip and is more install work. If you want to keep the machine as a collectable with occasional use it is recommended to not make any modifications and use the machine as it is.

Edited February 5, 2021 by Sugarland

[ACML]

Congratulations!  The no PWR LED is common.  The fix is simple.  The three red LEDS are on a little green printed circuit board (PCB) that snaps into the top shell housing.  What happens is the solder pads on the LED leads into the PCB used very little solder and they develop a crack and de-bond (no continuity, no light).  Take the top shell off, and turn the top shell over so the keyboard is facing down.  You can see the little LED PCB (back side).  Just retouch the 6 solder pads for the three LEDs with more solder to ensure continuity.  Done.

 

Bob Woolley's 1200XL keyboard fix on retrobits.net works great.  I recommend BARE conductive paint for the keyboard repair.  The 1200XL OS should run Pacman fine, especially if you are using a real cartridge.  Have you tried a different joystick?  Also, if you have two joysticks, try the one that you're using now in the second port and try two player Pacman. If player one still has an issue, then that's a head scratcher.  

 

The video quality is poor (composite and RF) and there is no Chroma signal on the monitor port so you'll just get B&W.  A lot of folks like the UAV video mod, but for the 1200XL, I have found the ClearPic2002 mod to provide an excellent signal and like the UAV, it returns Chroma to the monitor jack for sharp S-video.

 

There is a newer version of the OS called Rev 11 that is a lot more compatible than the stock Rev 10.  Best Electronics sells the Rev 11 ROMs.  

 

Enjoy!

 

[800_Rocks]

16 hours ago, ACML said:

The 1200XL OS should run Pacman fine, especially if you are using a real cartridge.  Have you tried a different joystick?  Also, if you have two joysticks, try the one that you're using now in the second port and try two player Pacman

Sugarland and ACML thanks for your great replies.  Until I fix the keyboard I can’t select two player PacMan to try the 2nd joystick port ?  However my joystick worked perfectly with DonkeyKong so I hope Sugarland’s answer is right... an incompatibility with that game??

Edited February 5, 2021 by 800_Rocks

[800_Rocks]

16 hours ago, ACML said:

The video quality is poor (composite and RF) and there is no Chroma signal on the monitor port so you'll just get B&W.  A lot of folks like the UAV video mod, but for the 1200XL, I have found the ClearPic2002 mod to provide an excellent signal and like the UAV, it returns Chroma to the monitor jack for sharp S-video.

Oddly using the monitor out on the 1200XL with the cable I use on the pictured Commadore 1702, rear connection with separate Chroma and Luma inputs looks darn good to me as is. 

[+DrVenkman]

3 hours ago, 800_Rocks said:

Sugarland and ACML thanks for your great replies.  Until I fix the keyboard I can’t select two player PacMan to try the 2nd joystick port ?  However my joystick worked perfectly with DonkeyKong so I hope Sugarland’s answer is right... an incompatibility with that game??

There's no incompatibility with PAC-MAN. It works fine on any A8 in my experience.

3 hours ago, 800_Rocks said:

Oddly using the monitor out on the 1200XL with the cable I use on the pictured Commadore 1702, rear connection with separate Chroma and Luma inputs looks darn good to me as is. 

As mentioned above, the stock 1200XL doesn't support Chroma on the video jack. The signal is physically not connected. However, there's a quick & dirty mod to add the Chroma signal by soldering a single wire  to add it back.  Further, it's also possible to connect things by running Luma to the Luma jack of a monitor, and running Composite to the Chroma jack. Some monitors do a decent job with internal comb filters so that this will give a relatively clean image. If you take the same cable you have connected to the Chroma input on the back of your 1702 and plug it into the (composite) Video input on the front of the monitor, what do you see when you move the switch on the back to select the front panel inputs?

 

EDIT: I just pulled out my second 1200XL that is stock aside from a UAV video mod and swapping in the rev 11 OS ROMs (burned to EPROMS by me, which I did last summer). No problem whatsoever with PAC-MAN either from a physical vintage cartridge or loaded from my SIDE3 cartridsge.

[_The Doctor__]

Your problem is not incompatibility, it's the keyboard, once you fix it up you'll be able to play two player pacman.

 

You can use the test set disk that's been floating around atari age, it will provide keyboard and port testing in on of it's many choices...

 

In the mean time... without any peripherals plugged in at power on the Atari symbol rainbow should be on screen, tap the the help key and you should have the self test screen, there you can test keyboard, memory, sound, etc.

[800_Rocks]

15 minutes ago, _The Doctor__ said:

Your problem is not incompatibility, it's the keyboard, once you fix it up you'll be able to play two player pacman.

 

You can use the test set disk that's been floating around atari age, it will provide keyboard and port testing in on of it's many choices...

 

In the mean time... without any peripherals plugged in at power on the Atari symbol rainbow should be on screen, tap the the help key and you should have the self test screen, there you can test keyboard, memory, sound, etc.

Keep in mind this oddity... the same joystick in the same port works perfect for Donkey Kong but does not work for PacMan.

I will look for the test desk (.ATR) thanks!

 

No keys work, none, nada so I can't press Help until I perform mylar surgery this weekend.  I do get the nice rainbow Atari logo when no cart or SIO boot is plugged-in and Donkey Kong plays, sounds and looks great.

[_The Doctor__]

some games require you to press select to select number of players other games just require you press the second players trigger or select it with the first stick, this is normal. You more than likely will be fine once you fix up the 1200XL keyboard using some conductive pen/paint (BARE or CAIG, etc) lots of write ups and video on how to do it.

[Gunstar]

wrong thread

 

Edited February 6, 2021 by Gunstar

[tjlazer]

Before you tear into the keyboard try pressing the keys really hard many times to see if they come to life.  I was able to get all of mine working by doing that.

[800_Rocks]

My 1200XL keyboard issue was definitely the classic Mylar connection issue described by so many others in this forum.  My removed Mylar is shown at the top. You can see how the 9 leads (arrow 3) have been completely torn away from the mylar over time.  The torn/separated leads are stuck to the tape (arrow 2) that was originally binding the leads to the  board connector (arrow 1). In this picture I have already cleaned the board connector. Before cleaning it was covered by the residue from the tape. It was easy to see why no signals were making it from mylar to board. 

 

[gozar]

On 2/5/2021 at 10:41 PM, 800_Rocks said:

Keep in mind this oddity... the same joystick in the same port works perfect for Donkey Kong but does not work for PacMan.
 

Donkey Kong may read the joystick differently than Pacman. Start up basic and run this code:

10 ? STICK(0)
20 GOTO 10

Now, move the joystick to the different directions. These are the values you should get for the different directions:

     10  14  6
       \  | /
        \ |/
     11--15--7
        / |\
       /  | \
      9  13  5

 

[ACML]

On 2/7/2021 at 7:36 AM, 800_Rocks said:

My 1200XL keyboard issue was definitely the classic Mylar connection issue described by so many others in this forum.  My removed Mylar is shown at the top. You can see how the 9 leads (arrow 3) have been completely torn away from the mylar over time.  The torn/separated leads are stuck to the tape (arrow 2) that was originally binding the leads to the  board connector (arrow 1). In this picture I have already cleaned the board connector. Before cleaning it was covered by the residue from the tape. It was easy to see why no signals were making it from mylar to board. 

 

Assuming you haven't put it all back together, please throw away the tape (#2 in your photo) as it is the culprit of the infamous problem.  You don't need it anymore.  I assume it was there to ensure contact (extra thickness) between the PCB and mylar.  It oxidized over time and viola, no continuity.  When you repaint the 9 fingers #3 in photo,  make sure all conductive material is same thickness (height).  Common first time mistake (been there, done that) is to have one or two fingers thinner than the others so when you reassemble, those fingers don't make good contact.  Just make sure the build up of paint on all nine is of uniform height.  Tip:  I like to use a toothpick to apply BARE conductive paint as it gives great control.  If one or two keys still don't work and are common to the same finger terminal point, you may likely find out that you damaged a trace while removing the mylar from the PCB.  You can use a multimeter to test for breaks in continuity along a trace to identify where the break is. If the break is under the white silicon spacer material, gently pry it away, lay down the conductive paint to repair break, allow time to dry and lay white spacer back in original spot (again, been there, done that).  This conductive paint has some resistance, so even though you may no longer get a "beep" on your multimeter for continuity, it will still work. 

  

Edited February 8, 2021 by ACML

[800_Rocks]

On 2/8/2021 at 3:27 PM, gozar said:

Start up basic and run this code:

10 ? STICK(0)
20 GOTO 10

Now, move the joystick to the different directions. These are the values you should get for the different directions:

     10  14  6
       \  | /
        \ |/
     11--15--7
        / |\
       /  | \
      9  13  5

I got my keyboard working!  So on to joystick 0. When I run this program it is stuck on 13 instead of 15 and does this on two different (known good) joysticks. So any ideas on how to trouble shoot a faulty joy0?  BTW joy1 works fine/as expected. 

Edited February 18, 2021 by 800_Rocks

[StickJock]

That looks like your joystick thinks that it is always pointing down.  Does it do this with no joystick plugged in?

 

The down pin on the joystick port is pin 2, which is connected to pin 3 on the PIA chip.  The PIA is seeing this pin as grounded.  If you pull out the PIA chip, and test pin 3 of the socket without the PIA plugged in, is it connected to ground?  If so, there is some short to ground somewhere on your board.  If pin 3 of the PIA socket is not grounded, then the issue is with the PIA chip itself, as it thinks it is grounded.  One test you could do is to bend up pin 3 of the PIA before you put the chip back into the socket.  That way, it is completely disconnected to anything.  Then, if you run your joystick test, does it still show 13?  If so, then it is definitely a bad PIA.  If it shows 15, then you could use a wire to ground the pin that is sticking out and then it should show 13.  If so, then your PIA chip works properly (at least for this pin).

 

[800_Rocks]

Update on Joystick 0 issue - Even with no joystick attached it still reports the ‘Down’ pin on Joy0 is active. After checking all the pins, caps, resistors and traces for birth joystick ports I concluded there were no issues with those so I removed the PIA chip and replaced with another and that resolved the problem. So my 1200XL is now working great!!