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800 XL BASIC Crashes Constantly--help/advice needed!


lord_mike

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I will try to reseat the chips. This is my latest test program... Now the 600XL doesn't hang (neither starts the built-in test...), just stopped with error, after 1-2 secs of running.

What is error code 11? Where can I find the error codes defined?

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My guess is a bad socket as well. With multi tester in continuity test (beep) check continuity between each pin shoulder of the os rom chip (or any other chip like basic rom chip) and the next connecting point in the mother board or component(like resistor or other chip). 

I am almost sure you will find one leg that is not making good contact with the rest of the motherboard, because you re seat the chips and behavior changed. Something similar happened to me, when I re seat them I got different problem. 

You need to use Sam's book schematics or atari original schematics to help you to find the component which is connected with each particular pin of the osrom chip. 

Once you find the problematic pin you can use a small screwdriver to push and  help to make the connection of the pin and test your basic program again, if it work, you identified the problem, now you need to change the socket for a new one. 

Edited by manterola
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By the way. Is it normal to have all the chips socketed on a 600XL motherboard?

On the other hand I guess it was not common to replace the BASIC ROM with a custom 2764 this way? Unfortunately I don't have picture on the other side but it seemed to me normal PCB seat. From the solder side. No hacking, no patchwire..

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Edited by Sanyi
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Every 600xl I have seen is fully socketed.  Replacing the Basic ROM with an EPROM however is not that common, and that is probably where you problem lies. This required modification to the motherboard, so there could be some bad connections/shorts there.  I would start by carefully examining the added piece of socket and maybe reflow the solder on it. Also EPROMS do suffer from bit rot over time, so it could be bad too.

Edited by JR>
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5 hours ago, JR> said:

Every 600xl I have seen is fully socketed.  Replacing the Basic ROM with an EPROM however is not that common, and that is probably where you problem lies. This required modification to the motherboard, so there could be some bad connections/shorts there.  I would start by carefully examining the added piece of socket and maybe reflow the solder on it. Also EPROMS do suffer from bit rot over time, so it could be bad too.

 

Not all 600XL are fully socketed! ?

 

I wouldn´t assume that this mod causes the issue. For the extension from 24 to 28 pins for the BASIC it´s only needed to put in the missing pins for the socket and change the both "hardwired" jumper/bridges right beside the PBI. Because addresslines here are affected, any mistake would prevent the computer from starting. Also, if something attached to the EPROM would be wrong, the BASIC won´t run in any way.

 

To my conclusion would be: bad EPROM, bad memory or any defective around the RAM access. When EPROM and the RAM chips are excluded, I would change the DelayLine first.

 

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4 hours ago, tf_hh said:

 

Not all 600XL are fully socketed! ?

 

I wouldn´t assume that this mod causes the issue. For the extension from 24 to 28 pins for the BASIC it´s only needed to put in the missing pins for the socket and change the both "hardwired" jumper/bridges right beside the PBI. Because addresslines here are affected, any mistake would prevent the computer from starting. Also, if something attached to the EPROM would be wrong, the BASIC won´t run in any way.

 

To my conclusion would be: bad EPROM, bad memory or any defective around the RAM access. When EPROM and the RAM chips are excluded, I would change the DelayLine first.

 

I spent some time carefully inspecting the pictures in the post you sent and also the schematics of the 600XL and now I hope I understand what was the original purpose of the creator of this 24-28 pin layout.

Actually this is not that uncommon, I've seen this kind of trick in the Plus/4 MoBo also, but there it is specifically stated that 2364 <-> 23128 was the aim.

 

 

 

Thanks a lot for all the hints and tips for all of you!

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27 minutes ago, Sanyi said:

... and now I hope I understand what was the original purpose of the creator of this 24-28 pin layout.

Actually this is not that uncommon, I've seen this kind of trick in the Plus/4 MoBo also, but there it is specifically stated that 2364 <-> 23128 was the aim.

The 1200XL also has a 24/28 pin thing going on for the two OS ROMs. Some machines have two 28-pin sockets, and some have 24-pin sockets. Further, some early units have 28-pin EPROMs for the ROMS but most have 24-pin mask ROMs. Two of my machines have 28-pin sockets but both have mask ROMs sitting in them.  

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Mmmkey...

Checked the soldering, of the ROM sockets and they seems ok.

Both of ROM chips were removed and I've checked their contents. BASIC is revC (8kB), OS is REV-02 (16kB). Checked several times with my eprom burner (TL866CS) and they contained what they should. (ROM images are from here http://atari.vjetnam.cz/index.php?frame=roms, I guess they are OK).

For being sure, I took out the CPU and re-seated it.

Checked the continuity in the socket (seated ROM pin with CPU pin), all seemed fine.

Started my 600XL, no change. 10 goto 10 fails this time with error 12..

Started up a memory test and on the third round the first ROM bar turned to red...

 

Which one is the first ROM? In the service field manual I just read that the memory test should not be running more than 7 minutes, because of high risk of the image burning into my monitor, but it is not written, which bar is which ROM (and both of them described as 8kB ROMs)..

I dared to left the test running - I live my life dangerous and don't care about burnt monitor displays - while I was typing this reply. Both of the ROM bars became red.

WTF?

I think the RAMs are fine, at least they are green, DelayLine (RAS, CAS) should be OK. 

 

I wrote two 28C256's and executed the test again.. Well, when the OS was replaced with a 28C256 (2x 16kB, rev-02), the 600XL didn't boot.

When only the BASIC was replaced with a 28C256, the machine booted, but with the same symptoms. After a few minutes of memory test left ROM bar turn to red, simple basic infinite loop stops with an error after 1-2 secs.

(images were taken with original chips)

 

Next steps:

- I will replace the RAMs with 4464's (41464)

- new sockets for the ROMs and try to pursue my a fellow 600XL owner to lend me some of his ROM chips to test.

 

 

 

 

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Edited by Sanyi
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It was the CPU.

 

A generous 600XL owner I know lent me his whole computer. I switched the CPUs first: the infinite loop runs until BREAK is pressed, memory-test remains green. In his machine the loop stops with error..

 

 

Edited by Sanyi
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