atari 800xl boot problem

[SockPuppet]

Hello all!

Recently, I have gotten a hold of an ntsc Atari 800XL in a pristine physical condition but I am experiencing a weird behavior with it. I would say there are about 50% chances of this happening:

During cold boot the few seconds long initialization sound does *not* play, screen goes immediately to "READY" with blinking cursor, then when I try to execute any basic command (“list” for example or “bye”) the cursor goes to the next line and computer freezes in a way that I cannot type anything else until restart. Interestingly enough when I leave the Atari for few minutes in that state the usual color cycle screen saver kicks in, so the computer is not totally frozen. Pressing reset does not help ever to kick it into a proper mode, only power down can fix it. Generally after 2 or 3 tries it boots properly, basic works etc. and then when I reset it, it still continues to work fine until next cold boot when the lottery starts again. First thing I did was to order a modern power supply replacement but even after that the issue still occurs. All built in diagnostic tests pass every time - that is when the lottery lets me get into the test menu.

Unfortunately I do not own a spare Atari 800 to borrow the chips from to test so any suggestions would be appreciated.

Edited February 4, 2021 by SockPuppet

[Paul Westphal]

If the chips are socketed , try reseating them. Leave the lid off and let it run for a minute. Touch the main chips to see if they are hot or not. A really hot chip indicates a possible bad chip. Old school, but it works.

[flashjazzcat]

Does it do this immediately on a cold power up (after being turned off for hours), or only when power cycling? If the latter, then the symptom can indicate that the DRAMs are taking a while to lose their contents. This causes the OS to think a warm reset has been performed, and problems ensue. Waiting a few seconds more after powering off before powering on again usually fixes this.

[SockPuppet]

Thanks both for your replies, I followed the suggestion and reseated all (4) socketed chips, used a contact cleaner spray along the way.

The issue seems to happen only when power cycling, at least I was not successful getting it on the first turn after a longer shutdown.

Though I generally wait about 5 sec before switching it back on, is that too short perhaps? As far as I remember from owning an Atari 130XE back in the childhood, power cycling was never an issue and I doubt I waited more than 2-3 sec back then. However that was a newer 130XE and this is a bit older 800XL (circa 1983). I will try to wait 10 sec each power cycle and see if the issue disappears.

While performing the disassembly and reassembly another issue popped up, the keyboard was very sensitive form the beginning but now few keys (mainly return) are triggered by just looking at them, all other keys require very minimal force to operate as well so looks like a keyboard disassembly is at hand.

 

[SockPuppet]

I also checked the temperature of all the chips after running a memory test for a while and the warmest but not hot was the CPU then GTIA.

 

[SS]

I have a 64K modded 600XL motherboard that would not clear its memory for sometimes minutes at a time even though the machine would pass all of its self tests.  I eventually replaced the two RAM chips and suddenly everything started working OK.  Perhaps one or more of the RAM chips in your 800XL is experiencing a similar problem?  

[SockPuppet]

Just now, SS said:

I have a 64K modded 600XL motherboard that would not clear its memory for sometimes minutes at a time even though the machine would pass all of its self tests.  I eventually replaced the two RAM chips and suddenly everything started working OK.  Perhaps one or more of the RAM chips in your 800XL is experiencing a similar problem?  

That would make sense, for now waiting 10 sec when power cycling seems to work allright. Anything shorter than that and the issue comes back.

I will have to see how much of a hurdle will this be in the long run. Btw any suggestion of a good brand and model for the replacement ram chips?

 

[_The Doctor__]

up to 10 seconds is normal, you machine will survive slight power line issues better as well... I wouldn't swap out ram or caps unless it takes a bit longer or other issues develop

[mimo]

16 hours ago, SockPuppet said:

Btw any suggestion of a good brand and model for the replacement ram chips?

 

Anything that isn't MT branded.