KubaCZ Posted December 2, 2011 Share Posted December 2, 2011 I've got another 800XL yesterday, but it seems it's broken. It gives red screen on start. POKEY, ANTIC, GTIA and CPU seems to be working - I've tested them on my other Ataris. I can't test PIA because I don't have any board that has socket for it. I don't think it's ram problem, because I took 41256's from working 286 board to replace old ones. Also I have RAM320XL which can remap base memory to it's own sram. Maybe it's problem with OS/ROMs? I don't have any other to test it with and I don't have skill to take it from other board whithout destroying it. Btw: It seems it's very early model: serial number is 20132, every part is REV. A, it has older ANTIC (CO14887) and every IC is socketed like in A400. Quote Link to comment Share on other sites More sharing options...
KubaCZ Posted December 2, 2011 Author Share Posted December 2, 2011 I don't have any cart except Basic and Assembler one I've tested that OS ROM (it's the longer one, right?) on other board that has same problems and it gave yellow screen for while but now it's again red. I don't see any broken traces on any of those boards and I have 2 PIAs so it's less chance that they will be both broken. So it's MMU on both boards? Quote Link to comment Share on other sites More sharing options...
Rybags Posted December 2, 2011 Share Posted December 2, 2011 Try a cartridge that runs as a Diagnostic mode cart such as Star Raiders or Asteroids. And maybe try the OS in another machine. If the chips you mentioned are all good though, then it might be the MMU or PIA, or a fault in the motherboard. Quote Link to comment Share on other sites More sharing options...
sloopy Posted December 2, 2011 Share Posted December 2, 2011 Red screen commonly is a memory issue... did you connect all Pin1's of the 41256's to ground? also try replacing the 74x158's (there are two)... sloopy. Quote Link to comment Share on other sites More sharing options...
Rybags Posted December 2, 2011 Share Posted December 2, 2011 Can also mean a dud CPU - I stayed away from that and the RAM since he said he'd tried a RAM320XL, which bypasses all the internal RAM and much of the logic. Note though that to use the RAM 320XL on the 800XL, you have to give it power, either hardwired to PBI or using the joystick port cable. Quote Link to comment Share on other sites More sharing options...
sloopy Posted December 2, 2011 Share Posted December 2, 2011 Can also mean a dud CPU - I stayed away from that and the RAM since he said he'd tried a RAM320XL, which bypasses all the internal RAM and much of the logic. Note though that to use the RAM 320XL on the 800XL, you have to give it power, either hardwired to PBI or using the joystick port cable. Yes, CPU can cause it too, but he said he swapped CPU (and the other LSI's), so i didnt suggest that... MMU is the other possibility, especially with the RAM320XL not working also... sloopy. Quote Link to comment Share on other sites More sharing options...
KubaCZ Posted December 2, 2011 Author Share Posted December 2, 2011 I think CPU is ok, in other (working) Atari is just working as it should. I can't change both 74158's, I have only one 74157. But RAM320XL solves that problem, right? RAM320XL seems to work without 5V supply. Quote Link to comment Share on other sites More sharing options...
sloopy Posted December 2, 2011 Share Posted December 2, 2011 I just did some tests with a known working 800XL (yes NTSC), and with the mem and 74LS158's removed, the machine would startup with a RAM320XL connected, with and without power hooked up... Also, if a specific DRAM has failed in 'chatty' mode, or 'stuck high' mode, the machine wont work even with a RAM320XL in it, until the DRAM is removed... sloopy. Quote Link to comment Share on other sites More sharing options...
KubaCZ Posted December 18, 2011 Author Share Posted December 18, 2011 Finally got my hands on 800XL board with MMU socketed, so I tested it with MMU from faulty board and worked fine, but if I use working MMU in faulty boad it's still same. I've also removed all DRAMS and two 74158's, but results are same. Also I've tried PIA from 400, still nothing. Quote Link to comment Share on other sites More sharing options...
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