Barn find 800 has only one working key: Break

[ClausB]

Because R128 is connected to 5V, you can't tell much by measuring resistance between it and ground. Part of that is the whole resistance between 5V and ground of the whole board and all its unpowered chips (or slightly powered by the ohmmeter). You would even get different measurements if you swapped red and black leads, because of all the transistors and diodes in the circuit.

 

The fault must lie with the keyboard connection, since the good keyboard fails too. Dumb question: is it plugged in the right way round? Or maybe shifted by a pin or two?

[+kheller2]

Would this help? http://mixinc.net/atari/pinouts/keyxl.htm

[Kyle22]

Because R128 is connected to 5V, you can't tell much by measuring resistance between it and ground. Part of that is the whole resistance between 5V and ground of the whole board and all its unpowered chips (or slightly powered by the ohmmeter). You would even get different measurements if you swapped red and black leads, because of all the transistors and diodes in the circuit.

 

The fault must lie with the keyboard connection, since the good keyboard fails too. Dumb question: is it plugged in the right way round? Or maybe shifted by a pin or two?

If both PoKey and Z104 are removed, the measurement from PoKey pin 25 to +5 should equal the value of R128. Same with Z104 pin 3 to +5. You are not going through any unpowered chips.

[ClausB]

Yes, that's what I said in post #17. He was probing pin 3 of Z103, which is ground, and R128.

 

He proved the circuit works by shorting pairs of pins on the keyboard connector.

 

[Kyle22]

Yes, that's what I said in post #17. He was probing pin 3 of Z103, which is ground, and R128.

 

He proved the circuit works by shorting pairs of pins on the keyboard connector.

 

I was talking about Z104 pin 3, it goes to PoKey pin 25, and they are pulled up by R128.

Z103 pin 3 is grounded.

[ClausB]

Yes, so was I in post 17. But he was probing Z103 in his last post, right?

[Kyle22]

Yes, so was I in post 17. But he was probing Z103 in his last post, right?

No, he keeps mixing up Z103 and Z104. He measures resistance from both Z103 and Z104 pin 3 to R128. Z104 pin 3 and PoKey pin 25 are the only chips connected to R128.

Z103 pin 3 is grounded. I looked back and found the clear schematic, so sorry for any confusion when I mentioned the XL with the resistor.

[ClausB]

I don't read it that way. He gave readings for both Z104 and Z103 relative to R128. Those for Z104 look correct. And I explained above why those for Z103 are not meaningful.

[Kyle22]

Maybe I have been confused by him constantly referring to measuring Z103 pin 3 to R128. Z103 pin 3 goes to ground, and has nothing to do with R128.

 

R128 is a 47k pullup resistor connected from +5 to Z104 pin 3 and PoKey pin 25.

[Britishcar]

kheller2, thank you for the schematic.

 

Kyle22 and ClausB and everyone! Thank you both for the informative debate and all of your help on this journey. Kyle22, you're correct, in my ignorance, I was not aware that Z103 pin 3 has nothing to do with R128. I was probing for differences of any kind between a working motherboard and this one but the results wouldn't really have been very meaningful.

 

And...I now feel that I must disappoint everyone who has been so helpful on this thread since...the old girl started working on her own suddenly and without any warning whatsoever.

 

I can only attribute it to her original filthy condition. From right out of the box her disgusting (trust me, I've never seen anything like it) keyboard and PCB's refused to acknowledge keystrokes. Subsequently, every part of her was scrubbed and blasted clean with contact cleaner, etc. and still she refused to recognize her (or any) keyboard.

 

Then suddenly, this morning, on the workbench, she began to acknowledge keystrokes, likely for the first time in decades. The only explanation I can come up with is from ClausB's original thoughts that perhaps some non-visible piece of remaining dirt somewhere was the culprit. My best guess is that this is likely the case and that all of my pulling and reseating of POKEY and the 4051's, all my probing around, and the seating and reseating of the keyboard connector finally allowed the juice to flow somewhere where it wasn't before.

 

So...perhaps three lessons here.

 

One, you cannot visually trust a pressed (non-soldered) connection to truly connect even though you have cleaned the hell out of it without really confirming true continuity.

 

Second, Atari really built the hell out of these things back in the early 80's. This machine looked like it had been retrieved from a pirate ship at the bottom of the ocean complete with all the filth both inside and outside that you can imagine. And, unbelievably, it fired right up even though I couldn't really even move the power rocker switch all the way because of the filth and crap that had accumulated around it on the inside. But once all the dirt was removed, Atari's robust design sprang right back to life and the machine looks factory fresh inside and out.

 

Third, this forum and community of enthusiasts are the best. The amount of arcane knowledge that you guys possess is impressive and really allows this hobby to feel like a shared passion.

 

So thanks to everyone. She passes all RAM tests and SALT tests. If she continues to work reliably, I may pop a Newell FastChip in her next.

[ClausB]

Congrats for rescuing a fine machine! Your hard work has paid off so you can now enjoy her. Her name is Colleen by the way.

[ACML]

Just another testament to how well Atari made the 800. How many other complex devices, especially an electronic device, still work 100% after 30+ years? Congratulations, your persistence paid off. Many would have given up, but you accepted the challenge. I'm glad there was a reward in the end. I too found a hidden jewel last month, but my challenge wasn't as difficult as yours.

http://atariage.com/forums/topic/236744-turning-a-sows-ear-into-a-silk-purse/?hl=+sow&do=findComment&comment=3208548

Edited April 12, 2015 by ACML

[Britishcar]

 

[+kheller2]

That is very fitting. I'm very glad another Atari lives on.

 

Do you have a picture from before you started cleaning? Most of the time I'm too excited to remember to take pictures before ripping something open to clean and fix it.

Edited April 12, 2015 by kheller2

[Kyle22]

Very nice. I'm happy you got it working.

[+DrVenkman]

 

 

 

I'm jealous of the Amdex monitor.

 

(And congrats on getting her running again! I'm betting it was just a poor connection at the keyboard connector to the motherboard - probably dirt or a bit of corrosion that worked its way out during all your troubleshooting; I suggested something similar way back when, you'll recall. Having fixed, cleaned and/or refurbished 7 of my own A8 machines just last summer, I'm familiar with the simple things that can be missed or overlooked in the desire to test everything exhaustively).

[ACML]

WOW! That baby looks like you just pulled it out of a factory sealed box! My find last month was similar. I already had an 800, but my recent acquisition looks so good, I'll be keeping it as well. That is one handsome 800 you have there.

[Keatah]

Look'n smart!

[Britishcar]

DrVenkman, you were indeed right! I was so positive that every connection was sparkling that I got lost in the weeds and began to ignore that simple answer as a possible source of the problem. And yes, I pulled that Amdek right out of her retail box in the early 80's and she's still color-saturated and tack sharp today (with chroma/luma separation)!

 

kheller2, no, no good "before" photos. I really should have done that. The way she looks now involved tooth brush, tooth paste, rubbing sponges, contact cleaner, dish soap and lots and lots of very hot water. There were some purplish-black deep stains sort of "frozen" in the fine grain of the outer casing that nothing would pick up. I finally had to resort to a wooden toothpick dipped in alcohol which I poked and twisted into virtually each super tiny grain of the affected area until the end of the toothpick would grow dark and the case slowly, slowly would give up the stain in that area. The actual dirt, hair, and unidentifiable long dead insect parts washed away fairly quickly but some of that deep dirt...whew! But...the results were great. And it was oddly entertaining.

 

If I end up doing some similar, I'll photo document it similar to a good car restoration series of photos.

[ACML]

DrVenkman, you were indeed right! I was so positive that every connection was sparkling that I got lost in the weeds and began to ignore that simple answer as a possible source of the problem. And yes, I pulled that Amdek right out of her retail box in the early 80's and she's still color-saturated and tack sharp today (with chroma/luma separation)!

 

kheller2, no, no good "before" photos. I really should have done that. The way she looks now involved tooth brush, tooth paste, rubbing sponges, contact cleaner, dish soap and lots and lots of very hot water. There were some purplish-black deep stains sort of "frozen" in the fine grain of the outer casing that nothing would pick up. I finally had to resort to a wooden toothpick dipped in alcohol which I poked and twisted into virtually each super tiny grain of the affected area until the end of the toothpick would grow dark and the case slowly, slowly would give up the stain in that area. The actual dirt, hair, and unidentifiable long dead insect parts washed away fairly quickly but some of that deep dirt...whew! But...the results were great. And it was oddly entertaining.

 

If I end up doing some similar, I'll photo document it similar to a good car restoration series of photos.

What is your restoration secrets? I use Scrubbing Bubbles Bathroom foam and a toothbrush on the case parts and Windex on the keyboard. On the tougher marks, I use the Mr. Clean Magic Sponge on the case. How did you get the keys to look so nice? I'm always concerned not to use anything that can be abrasive so I'm curious how you use the toothpaste and on what parts.

Edited April 13, 2015 by ACML

[spookt]

Looks like you did a great job cleaning her up. Do I notice I fellow SIO2USB user too? Nice choice

 

[Britishcar]

ACML, great question about cleaning materials. Remember, I had to really attack this poor thing as the filth was old and deep.

 

Motherboard, PCB's in general: hot running water (under the sink) with spashes of Dawn dishwashing soap. A soft toothbrush to get around some components where the dirt had really settled. Rinse, rinse, rinse to get the soap off.

 

Aluminum chassis: hot running water (under the sink) with spashes of Dawn dishwashing soap and a toothbrush with toothpaste on tougher areas. Had to resort to a small flathead screwdriver on some of the crusty hard water deposits.

 

Keyboard keys: removed each one and soaked over night in (initially) hot water with dishwashing soap. Next day, wiped each individually with a cloth towel until I got a good shine.

 

Keyboard substructure: Hot running water, dishwashing soap, then when dry, contact cleaner on the connections.

 

Case and plastics: hot running water, dishwashing soap, toothbrush with lots of toothpaste. But the most effective thing was a Mr. Clean "magic sponge." Rinse, repeat. Resorted to wooden toothpicks with alcohol to get ground in stains out of the plastic grain.

 

spookt: Yes! That is a SIO2USB from Germany. I love that device! Portable and flexible and every known piece of software on one USB key. Picky about its ATR format, though.

[Tickled_Pink]

That is one hell of a job. And not an ounce of retrobrite.

 

Surprised you could use water on a motherboard. I have an old 16K Issue One Spectrum motherboard that could do with a clean. I'll have to give it a shot.

[flashjazzcat]

Some people appear reluctant to even wet the case, never mind the motherboard, which I find surprising. You can't beat soapy water and a toothbrush. I don't think caps necessarily like to be submerged for long periods of time, but as long as everything's bone dry when it gets power, I don't see a problem. As for the case: anything even mildly abrasive must be used with extreme care, since it's easy to completely wreck the texture of the plastic case. But the above is clearly an excellent restoration job, and it was 90 per cent hot water.

[Britishcar]

Thanks! As far as retrobrite goes, the case had absolutely no "burn." I think I should name it Gollum since it seemed to spend so much time in a filthy dark place out of the sun.

 

I also agree about being too abrasive on the case but toothpaste and the magic sponge both worked very well.

 

As far as water on motherboards--no problem. Don't soak them overnight or anything but lots of running hot water (use rubber gloves for your hands) and dishwashing soap. Then give it a day or two to dry before applying power and your components will look brand new.