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gbag

Weird 800 xl problem....any advice?

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Picked up a used 800 xl for a good price...turned it on and this is what the test screen does...I haven’t seen this problem before...anybody have any advice

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Hi gbag,

 

open it up and if the chips are in sockets, make sure they are seated correctly. If they are socketed, also check for any corrosion on the pins and clean.  Refit and test and see what happens. 

 

Also post an image of the internals.

 

Regards

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Could be several issues there, bad rom, ram and antic for a start?

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My first thought is ANTIC is bad with all those weird and incorrect characters, but it could also be a bad ROM, or possibly a bad logic chip in the address or data bus.

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I think Antic is probably OK unless it's a refresh issue.

 

The corruption is all on Ram based graphics - the last line of text is in the self test Rom area and seems fine.

The fact it's going to the memory test would indicate there's some issue with Ram.  Though it does seem good enough to be able to run the test.

 

But I'd also first go with the reseat on chips like Antic, MMU, Rams and select logic ICs.

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I did put in a pac man cart... and it goes right to the memory test..just as when the cart is no there.  No star raiders cart on hand...will take it apart and post a pic of the internals...thanks for the help guys...will get back to y’all soon.

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So going straight to the memory test means the OS is detecting a RAM failure... but the title is rendered straight from the OS ROM, which would seem to signal a wider issue not RAM or ROM related - like mayby sloppy timing from the LS08... if it was just antic, I would think it wouldn't directly affect the operation of the system.

 

Reseating chips is definitely a 1st step. Then swapping ROM, ANTIC, to another system test..

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I don’t have another Atari computer but I have a couple Atari 5200’s....do they have any of these chips to swap and test?

 

cheers and thanks guys

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26 minutes ago, Nezgar said:

if it was just antic, I would think it wouldn't directly affect the operation of the system.

Don't forget, ANTIC creates Phi0 to feed to SALLY so ... anything screwy in the clock circuit would mess up memory timing, etc. Though I don't think that looks like timing issue. A scope would probably find the problem pretty easily but without one it's all down to checking a few voltages with a meter and then chip-swapping into a working machine.

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7 minutes ago, gbag said:

I don’t have another Atari computer but I have a couple Atari 5200’s....do they have any of these chips to swap and test?

 

cheers and thanks guys

5200s have all the same chips, but the chance of finding socketed chips is much lower on the 5200.

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7 minutes ago, Geister said:

5200s have all the same chips, but the chance of finding socketed chips is much lower on the 5200.

If it's a 4-port unit, it's more likely to be socketed than a later-production 2-port. 

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I do have a 4 port model... I will open up my 800 xl and 4 port tonight and take some pics...I have a decent multimeter... but no scope

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I opened it up and it is a revision D...so I need to put sockets in on all the chips before I do anything else...that’s a bummer.  Do you guys think it’s worth reflowing solder before I resocket all the chips?  Is there a way to use a scope to narrow down the chips causing the issues?

 

Anybody have advice for resocketting chips?  My current set up is a solder braid and a variable temperature soldering iron...what’s the best way for someone with minimal experience?

 

cheers and thanks,

G

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I think your problem is with bit 2 of RAM. Here's why: sometimes space (ASCII code hex 20) shows as $ (24), Y (59) as ] (5D), M (4D) as I (49), and R (52) shows as V (56). All differences are 4 so that's bit 2 and that's U11 according to the schematic. Looks like an infamous uT chip and it's soldered in. :( One way to desolder a known bad chip is to snip off all pins and unsolder them one at a time.

 

BTW the 5200 doesn't have those chips so don't bother opening it.

Edited by ClausB
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29 minutes ago, ClausB said:

I think your problem is with bit 2 of RAM. Here's why: sometimes space (ASCII code hex 20) shows as $ (24) and R (52) shows as V (56). Both differences are 4 so that's bit 2 and that's U11 according to the schematic. Looks like an infamous uT chip and it's soldered in. :( One way to desolder a known bad chip is to snip off all pins and unsolder them one at a time.

 

BTW the 5200 doesn't have those chips so don't bother opening it.

Thanks for the advice!!!  So in theory I only need to replace the u11 chip?

Ill look around the forums for a website for replacement ram chips.  Should I go ahead and resocket and replace all ram if I have the model with crappy ram chips?

 

cheers and thanks,

g

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I would get 8 chips and sockets, and do only U11 first, just to get up and running. Then replace others when I had nothing better to do.

Edited by ClausB

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8 minutes ago, ClausB said:

I would get 8 chips and sockets, and do only U11 first, just to get up and running. Then replace others when I had nothing better to do.

Will do...thanks again for the advice...much appreciated.

Did some more tests and got the audio visual test to run

 

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While I search for myself...does anyone have recommendations for Ram replacement chips and sockets? In some posts people say to avoid the Micron Technology chips...which ones are recommended?

 

thanks guys,

G

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When I dug out my 130XE (320K), it also had some RAM issues.  I ordered my replacement RAM from Jameco - the same place that I ordered my upgrade RAM back in the 80s!

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1 minute ago, StickJock said:

When I dug out my 130XE (320K), it also had some RAM issues.  I ordered my replacement RAM from Jameco - the same place that I ordered my upgrade RAM back in the 80s!

I will lookup Jameco...what ram

chips should I get?

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I'm pretty sure that the 800xl uses 64Kx1 DRAM.  You should get 8 of them, along with sockets, and replace them all while you are at it.  You could just replace bit 2 and test to see if it works (probably will), but you might as well socket & replace them all.  I had a Micron 64Kx1 go out BitD on my 320XE, but I was able to use one of the old ones that I took out of the upper bank during the upgrade.  Fast forward 30 years, and when got out my gear, I had another RAM fail during storage.  I just ordered all new RAM and socketed & replaced them all.

 

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1 hour ago, ClausB said:

I would get 8 chips and sockets, and do only U11 first, just to get up and running. Then replace others when I had nothing better to do.

That is good advice.  And since you don't have a desoldering iron, I'd recommend the clip the chip legs and then remove the remaining leg pieces one at a time with tweezers or needle nose pliers.  Then you can clean the holes out with braid and you'll be ready for a socket and chip.

 

For sockets, get dual wipe or machined pin, avoid single wipe sockets.

 

 

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