Atarimax Product Discussion Forums

8MBit Cardridge not fully recognized
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Author:  mr-atari [ Thu May 13, 2021 1:25 am ]
Post subject:  Re: 8MBit Cardridge not fully recognized

Sorry mate, can't help you there.....

About 16 bit software, I use Oracle VM VirtualBox, running Windows XP on my Windows 10 machine.
Even my old EPROM burner works :-)

Author:  Thore [ Wed May 19, 2021 3:47 pm ]
Post subject:  Re: 8MBit Cardridge not fully recognized

So I finally got a socket out of an old PC card and a GAL16V8D chip burned with the GAL jedec File, next step is to test it in a real Atari.
I am very excited :) Hopefully this caused the bug in my Atari. But even if the behaviour is the same, the new MMU might work and I could offer new MMUs to others with problems with this chip.

Author:  Thore [ Sun May 23, 2021 10:41 am ]
Post subject:  Re: 8MBit Cardridge not fully recognized

I managed to get the old chip out, and a socket in. Then I tested it with my new selfmade MMU.
At first, everything seemed normal, but after I selected the game from the menu, the Atari still crashes. So the new MMU behaves exactly like the old one.
So this is good and bad news.
Good: I can create replacement MMU chips
Bad: The MMU was not the reason for the defect.

So what can also cause a crash in the higher memory mapping? PIA?

Thank you so far for any help you gave :)

Author:  mr-atari [ Tue May 25, 2021 1:25 am ]
Post subject:  Re: 8MBit Cardridge not fully recognized

mr-atari wrote:
Good question, could be anything.

Signals to/from the cartridge are managed by the MMU and the memory-logic.
Perhaps the delay-line is going bad and setting signals with the wrong timing.
That is what I would replace first.

Author:  Thore [ Tue May 25, 2021 2:26 pm ]
Post subject:  Re: 8MBit Cardridge not fully recognized

Best Electronics claim, if the delay line is broken, the whole Atari would not work. Do you have other experiences? Unfortunately this special chip is soldered and it cannot be produced with a chip programmer. So itmf it's broken, the only solution is to buy another 800XL ☹
In my case everything is working except big cartridges.
But the menu is displayed, only after selecting the game it crashes. Games loaded via SIO cable are working without any problems.
I checked PIA, Antic and GTIA with correct chips, but these are also correct.
Also RAM was replaced, too.
And MMU is also working.
BASIC and OS can be left out, because of known reasons.
Sally can also be left out.
Pokey to a high possibility, too.
Line cartridge S to MMU is working.
Line R5 to GTIA is working.
Line Map to PIA is working.
Also the resistors at the mmu seems okay.
So if it's not the delay line I don't know what else could be the reason.

Author:  mr-atari [ Wed May 26, 2021 1:52 am ]
Post subject:  Re: 8MBit Cardridge not fully recognized

I have experience with a bad delay-line (not brooken), yes.
memory expansion in one atari works, in another, not.
replaced it and it works.

on Facebook, there is a dutch guy, who makes these delay-line and/or has schematics.
it's a rather simple device, you can build one with descrete parts to. ... 2624680886

It has 5 outputs, ranging from 25 to 440 ns ... vHoltgcVJE

The other issue, could be an almost burned up CPU.


Author:  Thore [ Thu May 27, 2021 1:38 pm ]
Post subject:  Re: 8MBit Cardridge not fully recognized

So I talked to Robert, and he said, that most commonly the screen stays black with a defect delay line, and he doesn't think that caps are defect, so he suggests to test the Logic ICs.
Unfortunately all of them are soldered.
But if they can also be tested in circuit, I might get a chance by building a probing adapter and test the chips without desolder them, if this is possible.
This would be the next step in the strange journey of bug fixing my Atari ;)

Author:  Thore [ Wed Jun 16, 2021 3:09 am ]
Post subject:  Re: 8MBit Cardridge not fully recognized

I found a german company selling 74 logic chips. While they are being shipped, I bought another 800xl for cross repair parts.
The second one starts up with the self test indicating all ROM and RAM bars with red bars/squares.
Now for cross changing parts, this is not a good start, so what could cause it? My first guess is the MMU, so I will try to replace the old chip with my selfmade MMU and test if this was the problem :)

Edit: I replaced the MMU from the second Atari, but this did not solve the problem. At least this chip is now socketed. Then I tested all RAM chips, finding two bad ones which I replaced, for all the others I cleaned all contacts and bent the pins. Now this second 800xl works fine.
And for not to be off topic: here the 8MBit Atarimax cardridge also works!

I am excited for the repair process of the first one, where the cardridge still fails...

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