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Mini Saga: Restoring my Childhood 800XL

800XL restoration restoring

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#1 TangentAudio OFFLINE  

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Posted Sun Mar 19, 2017 8:34 PM

Today I started the long process of trying to restore my childhood 800XL.  I received it as a Christmas gift in 1984, and it served me well for years as my platform for learning programming, and maybe more importantly, meeting lots of other people via the BBS scene in the late 1980s.  Eventually my interests in programming would merge with my interest in electronics, and this Atari was one of the most important pieces of the puzzle that eventually lead to my career in embedded software and hardware.  Years of playing with circuits via the Forrest Mims III books from Radio Shack combined with later discovering the book Your Atari Comes Alive by Richard Leinecker, led to the moment of epiphany when I understood the power of computers not only reacting to the world, but being able to control it.

 

I more or less ruined this Atari as I took my first fledgling steps attempting to learn the craft of hardware hacking.  I utterly destroyed the case.  First, drilling holes in it to add the hidden function keys.  Then, for some reason, I cut most of the cartridge area out.  At some point I had been fancying PC tower cases, so I made one out of wood and plucked the 800XL from its plastic case and put the computer into a fake tower case, complete with detached keyboard via a ribbon cable extension.

 

Eventually I gave up on this computer and had convinced my parents to get me a 65XE, which failed not due to my tinkering.  It was replaced by a 130XE, and then eventually my first PC around 1990.

 

Anyway, I've held onto this thing all these long years.  It's still a complete mess, but I assumed one day I'd get it working again.  I was hoping today would be that day, but the saga has only begun.

 

 

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#2 TangentAudio OFFLINE  

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Posted Sun Mar 19, 2017 8:37 PM

The only record of the "tower" case I made, along with the detached keyboard, is a terrible low-res picture that I took with a video camera connected to a ComputerEyes digitizer... It's hard to make anything out, but the black box with the white panel is the "tower," and the keyboard (as shown above) is also in this picture.

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Edited by TangentAudio, Sun Mar 19, 2017 8:38 PM.


#3 TangentAudio OFFLINE  

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Posted Sun Mar 19, 2017 8:39 PM

Some identifying marks on the patient...

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#4 TangentAudio OFFLINE  

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Posted Sun Mar 19, 2017 8:41 PM

I started by cleaning the board with isopropyl, and I've also started to undo some of the modifications.  I also unsocketed every single IC and liberally coated each socket with CAIG DeOxIt spray.  I've replaced a couple of capacitors, and tested continuity on a number of suspect looking traces.

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Edited by TangentAudio, Sun Mar 19, 2017 8:43 PM.


#5 TangentAudio OFFLINE  

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Posted Sun Mar 19, 2017 8:50 PM

Unfortunately, I'm still getting no visual indication of boot.  I've tried both my composite and S-Video monitor cables.  My monitor sees a sync, but the screen remains black.

 

I've done some minimal probing around on the 6502 and I can see the 1.79MHz clock.  I've also seen signs of life on several of the other important signals.  Based on the bus activity and current consumption change over time, it seems like it may be booting, but I'm just not getting any display.  Unfortunately this is all I had time for today...

 

I have a parts 800XL coming from ebay this week - I was originally hoping my board would just work, but it looks like it will be a bit more involved.  I'm hoping to use the case from the ebay unit (which is a bit yellowed unfortunately) and put together a working system.  It's very important to me to revive my own board for purely nostalgic reasons.  I think I can accept that it will be in different plastics.

 

I've also considered that this may remain my "hacker" Atari.  I have an U1MB and a SIDE2 on the way, and maybe this is the ideal recipient (assuming it's recoverable).  It fits right in with the history of the machine.

 

I also have a known-good original 800, and a 130XE that at least worked the last time I booted it up a decade ago... But you always remember your first.

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#6 Bill Lange OFFLINE  

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Posted Sun Mar 19, 2017 8:50 PM

Love this!

 

I destroyed my original 810 case by installing a "Write Protect Override Switch" and a "Write A Bad Sector Switch".  I removed the keyboard overlay from my original 400 to cut out the individual characters to put on a full struck keyboard that I wired up.  I also installed a "Speaker Shut Off Switch" for the internal speaker for those late night programming marathons.



#7 tjlazer OFFLINE  

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Posted Sun Mar 19, 2017 8:53 PM

I'm sure you can find a new case for it on eBay or something, maybe hit up B&C or Best elec.

Edited by tjlazer, Sun Mar 19, 2017 8:54 PM.


#8 TangentAudio OFFLINE  

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Posted Mon Mar 20, 2017 6:33 PM

The donor 800XL arrived from an ebay purchase, bought "as-is."  No keys working when I booted it up - but it did boot at least!  The video also looks terrible; maybe this is just how bad 800XL monitor outputs looked and I'd forgotten.  I most recently booted a classic 800 on my monitor and the output was gorgeous by comparison.

 

This unit has a different country of origin - my original is a Hong Kong / Chelco unit, REV A2.  The donor was made in Taiwan, and is a REV C board, with a "KALEX" identifier in the back copper. 

 

I haven't extensively compared the case plastics, but my original does have CHELCO stamped into both halves and the donor just has part numbers stamped.  Unfortunately this case is fairly yellowed across the top.  Maybe it will be a good retr0bright experiment.

 

The last major difference I noticed between the two is that this one has the "low" style RF shielding, which is screwed together through the board.  My original has the "high" style with the extra bend in it, and it fits together with bent tabs.

 

I happened to stumble upon the seller's YouTube video with the exact unit I bought, and apparently he had snagged the keyboard out of it to revive a different 800XL.  That might explain why this one is completely dead, and it also might explain why it has an almost identical keyboard mechanism to mine, which it doesn't seem like it would given the different factory.  Good news for me though because my keyboard was in rough shape and I needed parts anyway.

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#9 TangentAudio OFFLINE  

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Posted Mon Mar 20, 2017 6:40 PM

Now, on to the good news!  After some methodical chip swapping, I discovered I had a bad RAM chip (U10).  That at least got my 800XL booting, but the colors were off, like it was having some kind of luma problem for bright text.  I swapped U20 (CD4050) and the colors came back to normal.

 

I also opted to swap out my BASIC ROM, as pin 12 had completely disappeared due to some kind of corrosion!

 

Now my board boots to BASIC fine and produces correct color video.  It, too, is fuzzy and nasty looking.  I guess I'm in for some video circuitry tweaking...

 

Next up is figuring out if I can build one good keyboard out of the donor plus my original (which is entirely missing the mechanical parts for Reset/Option/Select/Start/Help)...

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#10 DrVenkman OFFLINE  

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Posted Mon Mar 20, 2017 7:21 PM

Awesome story! If you want the best quick & dirty video upgrade on an 800XL, it's hard to beat this one by the esteemed Bryan, who later created the great little "UAV" video board mod. I did this to one of my 800XL's until I put a UAV into it. But for a hacked up machine like you've got, this will fit right in!

 

http://atariage.com/...or-800xl/page-1



#11 TangentAudio OFFLINE  

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Posted Mon Mar 20, 2017 8:04 PM

Based on what I learned via that YouTube video, the previous owner of the donor 800XL had attempted a keyboard repair for his main 800XL, and gave up in favor of a swap.  So I ended up with his original keyboard, which he had tinkered with and then left for dead.  Once I got it open, I gave the mylar a bath with 99.9% isopropyl and tested it by itself.  Lo and behold, the mylar works just fine!

 

Also during disassembly I discovered five missing springs on the function keys, so that explains why those were totally dead.

 

I've opted to use my original keycaps, springs and plastic retention assembly with the donor mylar, backing plate and function key assembly.  My original mylar was in pretty rough shape, and for some reason I had shortened the pigtail by about 1" when I did the detached keyboard hack all those years ago.

 

I noticed my original keyboard had copper colored springs (except for break and return for some reason), while the donor had all silver.  Not sure if they are different force springs or not.  I noticed a couple of my springs were deformed, and this brought back some vague memories of fighting with this keyboard assembly probably three decades ago.  So I ended up swapping the entire upper row of springs for the ones in the donor, and took five more from the donor for the function keys.

 

After reassembly, I have a 100% working keyboard!  The outside is still pretty dirty, so it's all going to have to come apart again for cleaning, but at least I know I have good components now.

 

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#12 TangentAudio OFFLINE  

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Posted Mon Mar 20, 2017 8:21 PM

Running the critical system diagnostics cartridge.  WHAT'S WRONG?

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#13 TangentAudio OFFLINE  

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Posted Mon Mar 20, 2017 9:14 PM

Thanks for the pointer!  I gave this a try.. Vastly improved but still room for improvement.  Still getting small vertical noisy bars.. But it's much more legible now, and the colors do seem a bit better.

 

Awesome story! If you want the best quick & dirty video upgrade on an 800XL, it's hard to beat this one by the esteemed Bryan, who later created the great little "UAV" video board mod. I did this to one of my 800XL's until I put a UAV into it. But for a hacked up machine like you've got, this will fit right in!

 

http://atariage.com/...or-800xl/page-1

 

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#14 tjlazer OFFLINE  

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Posted Mon Mar 20, 2017 9:23 PM

I discovered something weird last week!  I have an Atari 800 and a 800XL and I used the same video cable.  The 800 looked like crap but the 800XL (which has been hooked up for a while with this cable and TV) looked great.  I was playing with the RCA cables at the end of the cable and discovered that the 800 needed the black RCA to be hooked up instead of the Red Chroma RCA!  It cleaned up the picture and looked great.  When I tried it on the 800XL, it was dark and crappy.  So maybe that is what is going on with your 800XL!


Edited by tjlazer, Mon Mar 20, 2017 9:23 PM.


#15 TangentAudio OFFLINE  

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Posted Tue Mar 21, 2017 6:45 AM

I discovered something weird last week!  I have an Atari 800 and a 800XL and I used the same video cable.  The 800 looked like crap but the 800XL (which has been hooked up for a while with this cable and TV) looked great.  I was playing with the RCA cables at the end of the cable and discovered that the 800 needed the black RCA to be hooked up instead of the Red Chroma RCA!  It cleaned up the picture and looked great.  When I tried it on the 800XL, it was dark and crappy.  So maybe that is what is going on with your 800XL!

 

Does your 800XL have a video mod?  Out of the box, most stock 800XL's can't do Y/C output (also known as S-Video) because the chroma pin was not connected on those models.  Both can do composite video (single RCA plug, usually yellow on monitors), which is vastly inferior but kind of the "lowest common denominator" standard.

 

In the photos I posted above, the blurry looking text was from a standard composite output (before applying the other modifications).  I didn't get a photo of the Y/C output before the mods, but it would have been in black & white because of the missing chroma signal on the monitor jack.  The photo on the right is with Y/C output going into the S-Video input on my monitor, and with the simple video improvement mods done.



#16 TangentAudio OFFLINE  

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Posted Tue Mar 21, 2017 11:37 AM

This hobby has a way of edging close to the insanity of restoring classic automobiles... Now I'm wondering if I should try to track down another Chelco 800XL as a donor for the plastics (and maybe RF shields) for maximum authenticity.  The Taiwan plastics of my donor are yellowed, and also don't seem to exactly fit my Chelco 800XL board, especially near the front edge of the case.  I'm sure I can make it work, but if anyone has a non-working Chelco, or even just the case plastics I'm interested.


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#17 JoSch OFFLINE  

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Posted Wed Mar 22, 2017 2:13 AM

When I hear that, I'm so happy (sorry Tangent), that I could pull my 800XL from my parents' attic and it worked right away.  :grin:



#18 TangentAudio OFFLINE  

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Posted Wed Mar 22, 2017 6:55 AM

When I hear that, I'm so happy (sorry Tangent), that I could pull my 800XL from my parents' attic and it worked right away.  :grin:

 

I think there's a fair chance this would have worked right away if I hadn't done such terrible things to it in my youth! :)



#19 JoSch OFFLINE  

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Posted Wed Mar 22, 2017 7:53 AM

 

I think there's a fair chance this would have worked right away if I hadn't done such terrible things to it in my youth! :)

I didn't, but I was a little surprised, that after at least 20 years in the attic' summer heat, the 800XL was just booting, as if I had stored it only yesterday.

No bad RAM, watchable display, the SALT tests running. I was stunned.



#20 TangentAudio OFFLINE  

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Posted Thu Mar 23, 2017 9:43 AM

I unearthed some ancient footage of the very Atari that I am restoring in this thread.  It is controlling a robotic arm that I built for a series of science projects when I was in high school.  This was filmed in early 1990.  I would go on to do many more iterations of this arm project, evolving it to run off of a PC via an ISA card that I built.  I even incorporated some very primitive image recognition into a later version.  I had bought a ComputerEyes for the Atari with some of the money I won from this science fair, thinking I could do some image recognition with that, but ultimately I went in a different direction.

 

The camera occasionally pans over to show the 800XL in all of its hacked up glory.  You can see the big gaping hole where the cartridge slot should be (covered with wood and electrical tape, if I recall), and the function buttons drilled into the top of the case.  I'm using an Amdek color monitor borrowed from a friend who had moved on from his Apple II.

 

 

And yes, I do have ATR files of many versions of the software that I wrote to control it.

 



#21 ClausB OFFLINE  

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Posted Thu Mar 23, 2017 9:51 AM

What was the interface to the motors?



#22 TangentAudio OFFLINE  

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Posted Thu Mar 23, 2017 10:00 AM

What was the interface to the motors?

 

Joystick ports 1 & 2, in output mode, as I had learned about in Richard Leinecker's Your Atari Comes Alive book.  The control electronics went through a few different iterations as I learned more about interfacing electronics to a computer.  My notes indicate that I was directly driving reed relays (which have a very small operating current) from the TTL outputs of the joystick ports.  These reed relays in turn actuated larger relays that I used to switch the motor currents.  The final iteration of the Atari version used transistors to actuate the relays, so it was a bit more "proper" in its implementation.

 

I was also taking advantage of the paddle inputs on the joystick ports to do primitive closed-loop position control.  Each of the joints of the robot had a potentiometer mounted so it could sense the position of the joint.  In this way I was able to make simple repeatable tasks that the robot could run.  The video is a demo of one of those tasks running.

 

ph1_arm1.jpg

 

ph1_arm2.jpg

 



#23 slx OFFLINE  

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Posted Thu Mar 23, 2017 10:04 AM

Wow and thanks for sharing!


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#24 mytekcontrols OFFLINE  

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Posted Thu Mar 23, 2017 10:08 AM

I unearthed some ancient footage of the very Atari that I am restoring in this thread.  It is controlling a robotic arm that I built for a series of science projects when I was in high school.  This was filmed in early 1990.  I would go on to do many more iterations of this arm project, evolving it to run off of a PC via an ISA card that I built.  I even incorporated some very primitive image recognition into a later version.  I had bought a ComputerEyes for the Atari with some of the money I won from this science fair, thinking I could do some image recognition with that, but ultimately I went in a different direction.

 

The camera occasionally pans over to show the 800XL in all of its hacked up glory.  You can see the big gaping hole where the cartridge slot should be (covered with wood and electrical tape, if I recall), and the function buttons drilled into the top of the case.  I'm using an Amdek color monitor borrowed from a friend who had moved on from his Apple II.

 

 

And yes, I do have ATR files of many versions of the software that I wrote to control it.

 

 

That must have been so cool to see that in action at the time! I would think that would have blown the pants off of the competition in that Science Fair.

 

- Michael



#25 TangentAudio OFFLINE  

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Posted Thu Mar 23, 2017 10:25 AM

 

That must have been so cool to see that in action at the time! I would think that would have blown the pants off of the competition in that Science Fair.

 

- Michael

 

Thanks!  I did very well competing in a total of 12 science fairs with ongoing iterations of the project (3 smaller iterations per year of high school, with a major re-implementation or large new feature each year).  First and second place awards, and a fair amount of cash prizes and scholarship money which helped pay for some of college.  I believe I won a $500 prize at the science fair in this video, and it directly went into Atari stuff - a 130XE, XF551, SpartaDOS X, and ComputerEyes.  A couple months later I won a bit more money and was able to afford a very bare bones 286 PC, and that was the beginning of the end for the Atari as being my workhorse computer.   I remember distinctly it was a debate between a hard disk interface for the Atari or that PC... Bittersweet memories, for sure, but in terms of the potential the PC unlocked for programming languages and growth as a future engineer, it was the right choice.

 

By the final iteration, I had rebuilt the arm out of aluminum, built much better electronics (including an ISA card), made a primitive image recognition system which could automatically pick up objects placed on the table, programmed a GUI from raw graphics primitives in Turbo C, etc.  Super fun stuff, and it laid all of the groundwork for what would turn into a pretty enjoyable engineering career.  And it all started with Atari!

 

arm_overall2.jpg interface.jpg

 

ph3_isa.jpg guiall.jpg


Edited by TangentAudio, Thu Mar 23, 2017 10:28 AM.






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