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TapperP

Atari 800 - what causes it to freeze sometimes?

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So I bought an Atari 800 from a forum member a couple of weeks ago. It's in beautiful looking condition, but I've been having trouble with it freezing sometimes.

 

What I mean is that with some games after a period of time it will freeze up and become non-responsive, and has to be power cycled.

 

My first thought was a bad RAM board, and after testing extensively with SALT 2.07 running from a Maxflash cart, I'm perplexed. Before reseating and switching the boards and using a little compressed air I did get a bunch of RAM failures in SALT. But after reseating the RAM passes, in fact it passed for over 150 cycles.

 

And yet with some games it will still freeze after some time. An example would be Repton by Sirius Software. Other games, like Defender, seem to never freeze.

 

The seller is sending me an extra RAM board to try, but like I said the RAM seems OK now in SALT.

 

What could be the problem with this 800? Really bummed because I used to own an 800 decades ago and was so happy to have one again.

 

I bought some electrical contact cleaner and may try cleaning the RAM sockets and board contacts, but they look very clean already. I just hope there isn't something more insidious wrong somewhere on the motherboard, as I have no electronics skills to fix it.

Edited by TapperP

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So, freezes to the point System Reset does nothing I guess?

 

Any screen corruption?  What's the Ram board config?

 

Could try swapping Ram boards around, like swap the furthest away with the closest one.

Are the Ram boards enclosed?  Do they get too hot if so?  If bare boards, is the retaining mechanism across the top to stop them moving around?

 

That system can be a pain to diagnose since there's multiple boards and every socket joiner is a potential point of failure.

Another common fix attempt can be to lift slightly then reseat all socketed chips on mainboard and CPU card, and Ram boards if they're socketed.

 

Defender if run from cartridge - it only uses the first 16K.  Repton I think is a 32K minimum game.

Edited by Rybags

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Shame that Repton is 48K, a smaller K game that freezes could help with swapping the ram boards around or taking one or best two out if you have a 16K game that freezes..

 

If you don't have a game like that then do what Rybags is saying and reseat all the socketed chips, those poor chips and sockets can get very oxidised over time. 

Edited by Mclaneinc

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Thanks for the replies. Later tonight I will open it up and do some reseating and cleaning.

 

Rybags -- it's 48K, 3 x 16K modules. They are all bare, not inside plastic casings. And yes, the retaining bridge is there as well. I have tried swapping before.

 

When Repton freezes, even the Reset button does nothing. It just froze again after only maybe 10 minutes.

 

Edited by TapperP

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Possibly but Rybags etc would be a better person to get tech from, screen corruption can come from ram as well so best to narrow it down bit by bit (no pun intended), give it a reseat..

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Screen corruption can sometimes indicate the Ram is bad.

 

From memory Slime should be a 32K game.  Shamus on original media/copy is for 16K, so is Nautilus.

 

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I’m guessing PIA or CPU. Lately I’ve seen many bad PIAs. To get correct error reporting from the diagnostic cart you really need the factory testing station with it, as it tests IO voltages which can be very telling.

Edited by Paul Westphal

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5 hours ago, TapperP said:

So I bought an Atari 800 from a forum member a couple of weeks ago. It's in beautiful looking condition, but I've been having trouble with it freezing sometimes.

 

What I mean is that with some games after a period of time it will freeze up and become non-responsive, and has to be power cycled.

 

My first thought was a bad RAM board, and after testing extensively with SALT 2.07 running from a Maxflash cart, I'm perplexed. Before reseating and switching the boards and using a little compressed air I did get a bunch of RAM failures in SALT. But after reseating the RAM passes, in fact it passed for over 150 cycles.

 

And yet with some games it will still freeze after some time. An example would be Repton by Sirius Software. Other games, like Defender, seem to never freeze.

 

The seller is sending me an extra RAM board to try, but like I said the RAM seems OK now in SALT.

 

What could be the problem with this 800? Really bummed because I used to own an 800 decades ago and was so happy to have one again.

 

I bought some electrical contact cleaner and may try cleaning the RAM sockets and board contacts, but they look very clean already. I just hope there isn't something more insidious wrong somewhere on the motherboard, as I have no electronics skills to fix it.

To make a long story short-and-to-the-point:

  1. Your minimum (and mandatory) set of spares for the 800: (x1) fully-populated CPU/GTIA/ANTIC board, (x1) 16K-RAM board and (x1) ROM board.
  2. A lock-up means code-execution crashed at some point. This means CPU crash, and for external or CPU-internal reasons.
  3. Use the 800's architectural strength to your advantage, and try first a quick-troubleshoot:
    1.  Start with RAM-board and plug spare sequentially on each slot (leaving other two with existing cards). Alternatively, find a title that requires <=32K and CRASHES. Then use your EXISITING ram-cards to cycle them between Slots-1 and Slots-2 only.
    2.  Move to OS-ROM card and replace with spare one (crash could also be related to bad-ROM region)
    3.  Then move to CPU-card and replace it with spare (this will require a bit more screws to get to, bu no chip-pulling / messing, etc.)
    4.  If at this point failure persists, you may have indeed a problem with wither Pokey and/or PIA, which will need individual spares (but does not sound to me like immediate suspects)

Since you ARE getting to run code, it means most of the system seems to be able to pull out of OS-initialization and boot-stage properly. You may want to consider running these specialized SW-tests, for as long as you can have patience for, and notice any crash (if failure occurs, try recording at which point it happens on either test, and repeat to verify if failure repeats at the exact same point, or if it occurs at another random one):

 

acid800-1.2-Beta.atr

 

Although originally designed for testing compatibility and timing accuracy of A8bit-emulation, they are also very handy to pull out deeply buried HW bugs (as I have done in the recent past).

 

Good luck!

Edited by Faicuai

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Let tests run over night.

to be a little more clear....

using a non cartridge game that uses 16k... run the game and play it as long as you can (if you have cassette) you can try one 16k card at a time.

using disk based games you would have two 16k cards in and rotate the cards round robin rotation till it fails.

remember the ram cards are in the 2nd 3rd, and 4th slots..

 

Edited by _The Doctor__

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Huge thank you to all who offered advice and expertise my way with this issue.

 

The person who sold me this 800 sent me a new 16K RAM board that just arrived today. First I replaced the rear RAM board with the new one and Repton again froze after maybe 15 minutes. Then I replaced the middle RAM board with the new one, and it has been running for over 4 hours now without freezing!

 

So, it's looking good so far... I'm gonna let it keep running and see how it does. If it makes it to 8 hours without freezing I think maybe the problem was that middle RAM board. That would be great if it's that simple. Fingers crossed!

Edited by TapperP
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UPDATE: 8 hours straight without freezing! 

 

I am now fairly sure it was indeed that middle RAM board, so it looks like maybe I'm lucky and it I just needed to replace it. 😃

 

Will test again tomorrow, but I'm very encouraged.

 

Thanks again to everyone who offered help - I always learn new things from you guys.

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11 hours ago, TapperP said:

UPDATE: 8 hours straight without freezing! 

 

I am now fairly sure it was indeed that middle RAM board, so it looks like maybe I'm lucky and it I just needed to replace it. 😃

 

Will test again tomorrow, but I'm very encouraged.

 

Thanks again to everyone who offered help - I always learn new things from you guys.

NICE (!)

 

Seems you hit the nail-in-the-head!

 

As you can see, the 800 is pretty easy to troubleshoot-and-fix (quickly), provided that you have some basic spares.

 

Cheers! 

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4 hours ago, Faicuai said:

NICE (!)

 

Seems you hit the nail-in-the-head!

 

As you can see, the 800 is pretty easy to troubleshoot-and-fix (quickly), provided that you have some basic spares.

 

Cheers! 

😃

Just passed another 8+ hours straight running Repton, in fact I'm playing the game now. I hereby declare this Atari 800 exorcised of its RAM devils.

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4 minutes ago, _The Doctor__ said:

Now you fix the old card and keep it for spare should any other fail... ;)

I don't know how to fix it... 😛 But I do have it wrapped up and safely stored for posterity.

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Does the old card fail right away if you put it in the first ram slot?

If so, then you can swap the ram chips, one at a time, into a good board in the first ram slot until you get a failed boot. Do this with each chip on the bad board to identify all of the bad ones. Then, just order replacement chips for them. 

 

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52 minutes ago, StickJock said:

Does the old card fail right away if you put it in the first ram slot?

If so, then you can swap the ram chips, one at a time, into a good board in the first ram slot until you get a failed boot. Do this with each chip on the bad board to identify all of the bad ones. Then, just order replacement chips for them. 

 

That’s a good basic troubleshooting technique, but the flaw might be a bad or corroded IC socket, or a bad discrete logic chip as well. I’d enjoy taking a stab at diagnosing and fixing it, but it would be purely academic. Two of my three 800’s are all already kitted out with 48K and the third has an Incognito in it, which means I’ve got three spare 16K boards already.

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I'd fix it, there's little point to storing broken stuff, it has a bad habit of being forgotten about and then when you dig it up you swap a failed board for an old failed board... leading you down a troubleshooting hassle/nightmare later... when it should be simple and easy. The ram cards are cheap to fix even if you wholesale replaced every chip on it. I think my last memory chip purchase was 100 chips for a little over 10.00 from some online seller. Even if you can't find that today it still wouldn't be much more. Or buy a back up card from Best / B&C or what have you and pass the broken thing on to someone who'll fix it.

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