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Trooper

Atari 800 strange problems

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So I've been trying all day to get one of my 800s to work but I'm encountering problems I've never seen before.

 

I connected the computer to the TV and to the powersupply, scanned for a channel and got one. However it only displays a black screen, very strange since the LED is lighting up and everything seems right, however, no memo pad just a black screen.

I put in a BASIC cartridge, no change still black screen. I change to a "Basketball" cartridge and now it lights up! Everything looks right and I can start a game by pressing "Start", however I don't have a joystick handy so that's as far as my testing goes. But it looks great. So I turn off the Atari and puts in Qix, black screen..... Centipede, black screen, I try about ten more games and they all give me a black screen apart from Basketball which seems to work great.
I have, of course, cleaned all the games thoroughly but that hasn't helped. Eventually I take off the top of the Atari to take a look at the memory modules. As expected there are tre 16K Ataribranded RAM cards but where I usually find an Ataribranded ROM card there's one marked "Atari 800S1" and "Elektroniktjänst Åkersberga" bland annat.

I suspect that's a swedish ROM and that it's failed for one reason or another since I get no memo pad?
The big question in my mind is why doesn't any games apart from Basketball work (or to a lesser degree, why the heck does Basketball work? :) )?

 

Is it possible to run the 800 on a single RAM cart (or does all the slots need to be populated)? My thought was that you could run the computer on a single module to see if one of the RAM modules are malfunctioning.

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You can run on a single ram cart. Just 16K or even 8K.

 

Once that's been eliminated it's time to clean all the contacts on all slots and carts. Then disassemble and clean/reseat all the chips & sockets. All standard faire for classic computer maintenance. And check the power supply too, be sure it is ripple-free, and putting out enough current at the right voltage.

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You can run with a single Ram module.

From the description my guess if you might have a bad chip in the OS board.

Some game carts are diag mode so sometimes work fine even if there is bad Ram or the OS is only partially working.

You could try opening up the OS module and slightly lift and reseat each large chip, with special attention the "E" one.

The "F" one should be OK otherwise the computer wouldn't run anything.

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@Rybags I was just going to write that Basketball *is* a diagnostic cartridge. So this points strongly to a bad OS ROM.

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@drac030 What are some other diagnostic carts? Also, do cold solder joints ever plague these machines? I know they can be a problem with radios from the same era.

 

Trooper, I would definitely open up the ROM case and try to apply some pressure on the chips and chip sockets. It only takes one bad connection to make things go haywire.

I don't know if bad solder joints are a problem with the 8-bits, but it is a possibility. Plenty of documentation on the web on what to look for and how to fix. Search for "cold solder joint"

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I also had the question, is there a list of Atari diagnostic cartridges? I now know of Star Raiders and Basketball. I have no idea whether many Atari carts were diagnostic carts, or whether only a very few were.

 

I was curious whether diagnostic carts run on an 800 with the OS ROM module removed, so I just tried it. Answer: Nope, neither Star Raiders nor Basketball start up in that scenario. So that foils one way to identify diagnostic cartridges.

 

I suppose even with a diagnostic cart you still need the OS for the one task of handing control over to the cart?

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Such carts are only diagnostic mode, as in they run immediately without the OS doing any system initialization.

The OS module still needs to be present. Asteroids is another diag mode cart. There are probably more, it was common practice for the very early Atari games.

Later on not so much. A much better method is to flag as a standard cart then let the OS do part initialization, then get control via the cart init vector but don't return.

Edited by Rybags

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@drac030 What are some other diagnostic carts? Also, do cold solder joints ever plague these machines? I know they can be a problem with radios from the same era.

 

Trooper, I would definitely open up the ROM case and try to apply some pressure on the chips and chip sockets. It only takes one bad connection to make things go haywire.

I don't know if bad solder joints are a problem with the 8-bits, but it is a possibility. Plenty of documentation on the web on what to look for and how to fix. Search for "cold solder joint"

Not so much cold solder joints but cracked ones surely on the keyboard and power PCBs. But that would not cause this problem.

 

Rather than push down on socketed chips you should pry them halfway up and then push them back in to scrape off corrosion. Definitely worth trying and it's pretty easy.

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It is also possible that one of your RAM boards has a bad chip in it that is preventing some of the larger games from playing. I had this problem once and could load smaller games but not larger ones. Try switching the RAM cards around too. Super Salt Diagnostics is what you need to really test the PC.

 

David

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@drac030 What are some other diagnostic carts? Also, do cold solder joints ever plague these machines? I know they can be a problem with radios from the same era.

 

Trooper, I would definitely open up the ROM case and try to apply some pressure on the chips and chip sockets. It only takes one bad connection to make things go haywire.

I don't know if bad solder joints are a problem with the 8-bits, but it is a possibility. Plenty of documentation on the web on what to look for and how to fix. Search for "cold solder joint"

 

I did take out to ROM card and took the chips about half way out and pressed them back but it didn't seem to make any difference, still the same problem. I decided I didn't have the time or space to keep troubleshooting and let it go to another collector.

 

Thanks for all the help and suggestions!

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