Atari 800 Troubleshooting - (check me please)

[Xebec]

I have 3 x Atari 800's.

 

#1 works perfectly (1 x ROM, 3 x 16KB RAM).

 

#2 doesn't power on*, but appears intact.

 

#3 doesn't power on*, and apparently had the SIO port was previously ripped off the motherboard.

 

Using #1, I've verified that the OS ROM and 16KB RAM boards from #3 work perfectly. I've swapped each of the 16KB boards into the first RAM slot to make sure. SpartaDOS/X boots and runs programs (SIDE 2).

 

However, *NONE* of the boards (ROM or RAM) from #2 work in #1.

 

Need advice:

 

I'm *tempted* to put a set of good ROM / RAM boards into #2 to see if it works, but I'm also thinking that if every single ROM/RAM board is bad in #2, then something on the motherboard may be frying the bus or boards?

 

 

 

* No power LED, and no output on monitor. Have removed/reslotted the boards a few times, and also jiggled on the power connector.

[+DrVenkman]

Until you're really confident with diagnosis/repair pocedures, set #3 aside for now.

 

As for #2, you're gonna have to take it apart and remove the RF shield to get a good look at what's going on inside. Uncased, plug it in and verify that 9VAC is making into the power supply daughterboard, and then verify that the correct voltages are coming out. Look for leaking or swollen caps, foreign objects, debris or signs of spilled liquids on the mainboard. Check for signs of prior work having been done on the boards that might have gone awry, etc. Post pictures of anything weird you see.

 

Anyway, just my two cents on how to get started.

[toddtmw]

Also, when it is apart an you are trying to power it up, don't forget to push the interlock switch down that the cartridge door pushes down when it is closed.

 

These things are tanks. If it is not getting a red light, I agree wiht DrV, start with the power supply. The Atari 800 is much more modular than the other computers. Swap out the different boards (once you have it apart) to see which board is causing the issue.

 

-Todd

[Xebec]

OK, I've taken her apart. It was missing one internal screw, so it was taken apart before. The PSU connector is a bit rusty or corroded, and I think the green cap right near the power switch is mis-shaped (the top is bulged a little bit). The cylinder shaped caps all look OK to my eyes.

 

Questions:

 

1. Can you safely plug in / power on the power supply board when it's separate/unconnected from the mainboard? (for testing / see if the LEDs come on)

 

2. Why is the cartridge door required to be closed? (interlock switch) My other 800 works perfectly with it open?

 

Bonus - What is the deal with the edge connector on the back / below the CPU - what was that intended for?

 

Pics of PSU area and overall boards: http://atariage.com/forums/gallery/album/1982-atari-800-repair-attempt/

Edited August 9, 2017 by Xebec

[toddtmw]

2. They didn't want you to remove or insert a cart with the power on. It should power off when the door is opened.

[Xebec]

2. They didn't want you to remove or insert a cart with the power on. It should power off when the door is opened.

 

If the door is already open is it not supposed to power on? That's where my confusion lies.. My existing 800 works with the door open.

[+DrVenkman]

 

If the door is already open is it not supposed to power on? That's where my confusion lies.. My existing 800 works with the door open.

No, it’s not. There’s a mechanical interlock switch. Some people disabled that back in the day. And sometimes the mechanical switch is either broken (shorted) or the plastic rod that actuates it gets stuck.

[toddtmw]

It should not work that way. If the door I open, the computer should be off.

[toddtmw]

We used to have to stick a pencil in there to keep it on so we could copy cartridges by running the copy program and then inserting the cart.

 

EDIT: Damn you autocorrect!

Edited August 9, 2017 by toddtmw

[Xebec]

OK - I found the clip inside that 'simulates' the cartridge lid being shut. The bad 800 at least now powers on, although it gives a buzzing noise on the monitor and only a faint green background (mostly black), with nothing else.

 

EDIT -

 

I got brave, and put in a known good OS ROM cart, and a good 16KB cart.. and it boots to memopad!

 

I put in 2 additional 16KB carts, and it was still good..

 

I then swapped each of the good cards with the original 4 cards, and *none* of them work..

 

What are everyone's thoughts on this behavior? Is there something that would one-time fry all four user-accessible boards (3x RAM, 1 x ROM) but not damage the CPU board or the rest of the PCB?

 

The only thing special I can see is the add-in boards look like they were touched.. they all have different types of RAM on them (2-3 types per board), and 1 is even missing a chip.. (one of the 4 on the bottom row). Is it worth pulling these ram chips off and testing them on good boards?

Edited August 10, 2017 by Xebec

[+DrVenkman]

If the RAM board is missing any of the RAM chips or 74 series logic, it won’t work all. Set that one aside. But none of the other two or the ROM board work in a good machine?

[Xebec]

If the RAM board is missing any of the RAM chips or 74 series logic, it won’t work all. Set that one aside. But none of the other two or the ROM board work in a good machine?

 

Correct --

 

The ROM board and 1 x RAM board are fully populated

2 of the RAM boards are missing the "bottom right" chip (if you are facing it) -- SN74L51ONDS (motorola) RQ8239 - socket Z501.

[+DrVenkman]

 

Correct --

 

The ROM board and 1 x RAM board are fully populated

2 of the RAM boards are missing the "bottom right" chip (if you are facing it) -- SN74L51ONDS (motorola) RQ8239 - socket Z501.

 

That's actually a 74LS10 chip; NDS at the end is irrelevant for our purposes. Good news is modern replacements are readily available online from electronics parts suppliers for under $0.70 each. Of course, with minimum order quantities, shipping charges and such it might be easier to order new RAM boards online from Best, B&C or eBay. Heck, maybe even the marketplace forum here. Given the uncertain condition of the RAM chips themselves, it might be worth sourcing at least one new board until you get the machine to boot.

 

The ROM board and still-complete RAM board issues are more difficult. Any sign that either board has been fooled with or modded in the past? Given the condition of the other two RAM boards, it almost sounds like someone did a RAM upgrade and maybe an OS mod to let the system access more memory. Any signs of old solder re-work or remains of solder on chip shoulders where a jumper might have been soldered? Any damaged traces? Are you certain all the chips are inserted in the correct orientations? If you remove the chips, examine everything very closely under bright light and magnification - Any chip sockets damaged (remove chips and examine socket wipes under light and magnification)?

 

For reference, I just took pics of all three RAM board and the ROM board from one of my 800's. This unit has never been modded and is bone-stock, mid-1983 production, right near the end. Here are good, high-res photos for comparison.

 

 

 

 

 

Let me ask as well - have you tried the populated boards in the other, working 800 to see if it will boot with them?

[Bryan]

Quick note on the interlock.

 

The FCC standards for a TV connected device were so strict in the '70s that I suspect the interlock was to make sure the lid's attached metal plate was firmly against the internal casting before the machine could be turned on. This meant cartridges didn't need internal shielding since they'd always be in a grounded metal box. What's amusing is that even though the brown carts have an aluminum back plate, it isn't attached to anything and thus is useless as a shield.

 

As soon as the lower standards for FCC class B were approved, we started getting smaller machines with stamped steel shielding like the 1200XL. I imagine this was one of the big reasons for the transition to the XL line.

[+DrVenkman]

 

As soon as the lower standards for FCC class B were approved, we started getting smaller machines with stamped steel shielding like the 1200XL. I imagine this was one of the big reasons for the transition to the XL line.

 

Sure, but even had the FCC struck a harder line in the Class B standards, something akin to the 1200XL would've happened anyway; the 400/800 were just too damned expensive. If nothing else, they'd have been redesigned to keep everything on a single board except the cartridges, even if they'd had to have kept a shield over the cartridge port.

[Bryan]

Slight derailment... Sorry.

Sure, but even had the FCC struck a harder line in the Class B standards, something akin to the 1200XL would've happened anyway; the 400/800 were just too damned expensive. If nothing else, they'd have been redesigned to keep everything on a single board except the cartridges, even if they'd had to have kept a shield over the cartridge port.

 

Well, it's a chicken and egg situation. The 400 and 800 would have had a longer shelf life if the market wasn't suddenly filling with Class B machines, so a cost reduced 800 became a rather urgent priority. Without Class B, designing a new model with full aluminum castings wouldn't have saved nearly as much. According to legend, it was TI's 99/4 testing failure that prompted Texas politicians to pursue a new set of rules.

[Xebec]

DrVenkman - great pics!

 

I did try earlier -- The populated board didn't work, and I placed a 'missing chip' on the two other boards, and the same thing.

 

There was some evidence the system was opened and worked on before -- one of the internal screws was missing. That's always possible a factory thing, but.. I'll assume it wasn't..

 

The RAM chips I'm having trouble identifying, each board seems to have a mixture of

AM9016DPC 8243DEP chips (AMD)

and

B8244AG MM5290N-4

 

The second part lists as a 16kbit chip (2 kilobytes) which makes perfect sense.. I'm assuming the AMD chip is the same, do I do not believe any upgrades were done.

 

The ROM board is the same revision as yours and looks good. I do nto see any burn marks, cuts or other stuff on these boards.. They simply do not work in this 800 or another 800 that I have that is good.

 

The rest of the system seems OK - the cpu board, main board, and power supply all work. That's why this is a bit odd.

 

I'll take a good look at this. I'm probably going to partially part out this 800 -- I have a case where someone screwed through the top stupidly.. I have a power supply board with the SIO port was broken off, and then I have these ROM/RAM boards that do not work.

 

I do have 2 fully working 800s with all 48KB and nice cases, so .. I'll just keep the main board and CPU board as spares if needed. The RAM hopefully gets replaced with an incognito 2 in the future on at least one of them anyway...

[+DrVenkman]

Slight derailment... Sorry.

 

Well, it's a chicken and egg situation. The 400 and 800 would have had a longer shelf life if the market wasn't suddenly filling with Class B machines, so a cost reduced 800 became a rather urgent priority. Without Class B, designing a new model with full aluminum castings wouldn't have saved nearly as much. According to legend, it was TI's FCC testing failure that prompted Texas politicians to pursue a new set of rules.

 

Yeah, fair points. So many variables - with tighter requirements, the VIC-20 and C64 couldn't have entered the market and begun undercutting Atari sales as well, at least not at the price points they did.

 

Anyway, Bryan, you're one of the sharper tools in the AA shed, after all. Do you have any suggestions for Xebec and his troublesome 800?

[Bryan]

I just fixed an 800 with a bad power supply board which is not that uncommon nowadays. Since these machines are socketed, the best thing is to swap until you find the culprit (once you know you've got good power).

[Xebec]

Yeah I'd say consider this closed for now.. Basically the 4 add-in boards from the SIO-damaged Atari 800 made another work..

 

So now I have:

2 Working Atari 800s, all original, 48KB, one with plastic covered cards and the other with 'bare boards'. Clean cases and keyboards.

 

1 non-working 800: damaged case (holes), damaged power supply board (broken SIO), bad ROM board, 3 x bad RAM boards, but good CPU add in card, and good main board. Dirty keyboard missing some keys .

[+DrVenkman]

Yeah I'd say consider this closed for now.. Basically the 4 add-in boards from the SIO-damaged Atari 800 made another work..

 

So now I have:

2 Working Atari 800s, all original, 48KB, one with plastic covered cards and the other with 'bare boards'. Clean cases and keyboards.

 

1 non-working 800: damaged case (holes), damaged power supply board (broken SIO), bad ROM board, 3 x bad RAM boards, but good CPU add in card, and good main board. Dirty keyboard missing some keys .

 

Not a bad situation to have; very similar to mine, actually:

 

1 x 48K machine that was originally 16K that has an after-market 32K board in it; slight crack on the upper/back area under the area covered by the removable top, but not noticeable from the front doesn't affect functionality.

1 x 48K machine cosmetically excellent but missing 3 keys

1 x 48K machine also cosmetically excellent but the plungers on several keys are cracked and don't return properly. I need to find a replacement keyboard for it at some point; in the meantime, it's a designated as a "key donor" for the others.

 

One of these will get an Incognito2 if/when Candle or Lotharek begins producing them. That machine will also go to a special spot in the man-cave; I've salvaged my old computer desk from my teenage years, complete with the cutout my step-dad built into the monitor riser when we constructed it, just big enough to pass an SIO cable through. I will pair it with a 1050 drive and 1030 modem, just like I had BITD. It'll be like being a teenager again, but with a huge, fast hard drive and way more RAM.

[Xebec]

 

Not a bad situation to have; very similar to mine, actually:

 

1 x 48K machine that was originally 16K that has an after-market 32K board in it; slight crack on the upper/back area under the area covered by the removable top, but not noticeable from the front doesn't affect functionality.

1 x 48K machine cosmetically excellent but missing 3 keys

1 x 48K machine also cosmetically excellent but the plungers on several keys are cracked and don't return properly. I need to find a replacement keyboard for it at some point; in the meantime, it's a designated as a "key donor" for the others.

 

One of these will get an Incognito2 if/when Candle or Lotharek begins producing them. That machine will also go to a special spot in the man-cave; I've salvaged my old computer desk from my teenage years, complete with the cutout my step-dad built into the monitor riser when we constructed it, just big enough to pass an SIO cable through. I will pair it with a 1050 drive and 1030 modem, just like I had BITD. It'll be like being a teenager again, but with a huge, fast hard drive and way more RAM.

 

That's great! The desk salvage is actually really awesome, that adds a lot to the nostalgia feel as far as I'm concerned.. The most I can do there is build some stacking wood constructions like my Dad had for holding modems, disk boxes, drives, etc.. . I still need to find an Atari 810 drive with the 1/3rd size flip lid -- that's what I remember having as a kid (1 of that style, and one of the 'full door' style, but the 1/3rd had the happy upgrade.. I have 5 x 1050s, 3 of which are USDoublers now..

 

Lotharek said the incognito 2 is coming soon!.. Does that basically have all of the functionality of SIDE + U1MB together? and no soldering required?

 

I thought I liked the 800XL form factor best, but after pulling these 800's out of the box.. that's not the case anymore. pun intended.

[toddtmw]

 

Not a bad situation to have; very similar to mine, actually:

 

1 x 48K machine that was originally 16K that has an after-market 32K board in it; slight crack on the upper/back area under the area covered by the removable top, but not noticeable from the front doesn't affect functionality.

1 x 48K machine cosmetically excellent but missing 3 keys

1 x 48K machine also cosmetically excellent but the plungers on several keys are cracked and don't return properly. I need to find a replacement keyboard for it at some point; in the meantime, it's a designated as a "key donor" for the others.

 

One of these will get an Incognito2 if/when Candle or Lotharek begins producing them. That machine will also go to a special spot in the man-cave; I've salvaged my old computer desk from my teenage years, complete with the cutout my step-dad built into the monitor riser when we constructed it, just big enough to pass an SIO cable through. I will pair it with a 1050 drive and 1030 modem, just like I had BITD. It'll be like being a teenager again, but with a huge, fast hard drive and way more RAM.

 

Pics?

[+DrVenkman]

 

Lotharek said the incognito 2 is coming soon!.. Does that basically have all of the functionality of SIDE + U1MB together? and no soldering required?

 

I thought I liked the 800XL form factor best, but after pulling these 800's out of the box.. that's not the case anymore. pun intended.

 

I don't know; surely some soldering will be required, won't it? Hmmm ... maybe the 800 ROM slot has enough bus signals on it to make that possible. Anyone have an original Incognito who can comment?

 

 

Pics?

 

Of ... ? The desk? It's currently covered by a bunch of my daughter's crap; now that she's moved out, we're moving her stuff out, getting rid of things and throwing stuff away. Right now the desk has a giant inkjet printer/scanner on it, along with a whole bunch of her high school stuff we're still sorting through. And the 1030 that will live on top of my drive is in a friend's hands. We haven't exchanged payment/shipping details but we'll get that figured out next week sometime.

[Xebec]

 

I don't know; surely some soldering will be required, won't it? Hmmm ... maybe the 800 ROM slot has enough bus signals on it to make that possible. Anyone have an original Incognito who can comment?

 

 

Looks like some soldering/wire work :

 

http://atariage.com/forums/topic/212773-incognito-install-a-collectors-perspective/

 

Maybe Incognito 2 needs less?

 

Also, does anyone know what the bus/edge connector on the back of the 800 main board is for ? the inaccessible one?