rubber_jonnie wrote: ↑Thu Nov 25, 2021 8:59 am
Ok, so looking at your pictures above, none of the jumpers are correctly set for 6 chip TOS.
Thank you, I am aware of that. In that same picture you can see that the mega was running on a two chip setup, so the jumper setup is correct. Trust me I have set all three jumpers correctly while switching from 2 chip to 6 chip setup (multiple times).
What should strike you as odd in that picture though, is not that the 2 chip TOS is being accompanied by a 2 chip jumper setup, but that there is no 74LS11 installed, while the 2 chip setup actually requires one to be. Installing one ordered from the webshop did not affect behaviour.
That oddity was already kind of answered bij Exxos. He said quite early that it's weird the 2 chip setup worked without the 74LS11. He then already predicted the chip select signals had to come from elsewhere. By turning it over, I think I've found it.
Following Exxos' and Troed's suspicion and by judging the label on the contraption itself:
This has probably been a switchable TOS, of which the new part was later removed. The old part still works, but only through 2 chip setup (black wire connected to "Old 2"?) and without the need of 74LS11. Since there is no wire connected to "Old 6", I think this is why I can't run a 6 chip setup. I have two directions to go:
1) see what happens when I remove "Old 2" wire and connect it to "Old 6". (This is quite easy and if it works, it works for me.)
2) Remove the whole contraption. (This means a lot more work if I have to revert removal)
After which I set the jumper configuration to six chip setup and install six chip TOS 1.4.
So I will try 1) first. The mega is already closed again, so it won't be before the weekend. Will get some pictures for you as well.
Thank you for thinking with me, I have only joined the online Atari community this year, but wow you guys are great! Please keep sharing your thoughts.