+slx Posted March 22, 2019 Author Share Posted March 22, 2019 I recently bought this heavily modified 800XL admittedly mostly out of curiosity and knowing it would not work reliably. I can‘t get it to run at all, not even with SysCheck 2.1. Any ideas what all this stuff might be good for? I‘d assume the board on the rear is a parallel interface but all the rest? Gesendet von iPhone mit Tapatalk Quote Link to comment Share on other sites More sharing options...
Rybags Posted March 22, 2019 Share Posted March 22, 2019 (edited) Looks like a +256K Ram upgrade as well. The horizontal row of LS chips, not sure but maybe it's used for the extra memory selection. Much or all of it looks one-off custom which is all well and good but a potential nightmare to diagnose. I guess you could try to restore the machine to stock if it doesn't start up. Chances are that there's just 1 or 2 dodgy connections or components that's a showstopper for everything else. Or maybe something's pressed down and caused a short. But like I said, not a fun thing to have to diagnose. Edited March 22, 2019 by Rybags 3 Quote Link to comment Share on other sites More sharing options...
+slx Posted March 22, 2019 Author Share Posted March 22, 2019 Thanks! I figured if I couldnt get it to run at least Id have a chipset for a 1088XLD 2 Quote Link to comment Share on other sites More sharing options...
SoundGammon Posted March 22, 2019 Share Posted March 22, 2019 I'd like to copy that OS chip and see what that's about! 1 Quote Link to comment Share on other sites More sharing options...
+SoulBuster Posted March 22, 2019 Share Posted March 22, 2019 There is a 256k memory upgrade and a parallel upgrade. At least some of that row of ICs in the front controls the memory. Beyond that I do not know. If you want to try to get it to run, re-flow the solder on all the connections that lead to the upgrades as a first step. Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted March 22, 2019 Share Posted March 22, 2019 There's an EPROM replacement for the OS ROM, but jeez, it looks soldered to the board? If you're willing to carefully desolder it (and replace a socket) and dump the EPROM, we can look at the OS dump and see what it is... Custom or whatever. the OS may be modified to support the custom parallel port as a P: device at minimum. I seem to remember a discussion about this system before - I've seen pictures posted somewhere, not sure if on this forum, or maybe on facebook while it was still listed on eBay - asking to determine what the parallel port board in the back of it was. 2 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted March 22, 2019 Share Posted March 22, 2019 I think the EPROM is piggybacked on the original masked OS ROM. Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted March 22, 2019 Share Posted March 22, 2019 I think the EPROM is piggybacked on the original masked OS ROM. Ah right... I see a selector wire going to pin 22? .... yeah that makes sense, 22 is Output Enable. So his switch on the right of the machine switches between the original masked ROM and the EPROM. Slx, have you tried powering it up with the switch in either positions? Regardless, if it's piggybacked, you could remove the top chip by carefully soldering + prying out each pin with a small flathead screwdriver 1 at a time simultaneously. Quote Link to comment Share on other sites More sharing options...
+slx Posted March 22, 2019 Author Share Posted March 22, 2019 While I might have the skills to unsolder that ROM I am quite sure I don't have the skills to put it back in again Would SysCheck be able to replace the piggybacked ROM as well? If so, something else is preventing a boot at the time, because it doesn't boot with SysCheck replacing all internal RAM and the OS ROM either. If I can't get it to run I can still put in on EBay and speculate it's an "early Tesla prototype board" as many of the chips are Tesla branded Would there be any places to look at with a logic probe to find out more about possible failure points (I don't have an oscilloscope). (It did not have a keyboard attached when trying but as to my understanding that's not required for Ataris to run.) Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted March 22, 2019 Share Posted March 22, 2019 While I might have the skills to unsolder that ROM I am quite sure I don't have the skills to put it back in again Would SysCheck be able to replace the piggybacked ROM as well? If so, something else is preventing a boot at the time, because it doesn't boot with SysCheck replacing all internal RAM and the OS ROM either. Yes the SysCheck is supposed to supplant the OS ROM... so yeah it would appear the issue is elsewhere. But then again, it also has a dip-switch mode that can supplant the internal 64KB RAM as well (but no 512K extended RAM)... so since you tried that, I would focus elsewhere... I think finding out whats on the at EPROM is worth the work to disassemble it, even if you can't replace it. The mask rom will still be there... and if you really want to put a dual OS back in, easy to program to a new chip... you could eventually put 2 ( or 4) on an EPROM use dropchecks or mr.robot's selector adapter... Would be good to verify the other easily swappable IC's work one at a time in another machine before we get to logic probing... Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted March 22, 2019 Share Posted March 22, 2019 Will need to fix those slider switches by the joystick ports, one looks salvageable.. the other not so much. wonder what they do. 1 Quote Link to comment Share on other sites More sharing options...
+slx Posted March 22, 2019 Author Share Posted March 22, 2019 Will need to fix those slider switches by the joystick ports, one looks salvageable.. the other not so much. wonder what they do. I think one switches the OS. They‘ll need replacement as the contacts look corroded and the sliders have come loose. Gesendet von iPhone mit Tapatalk Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted March 23, 2019 Share Posted March 23, 2019 clean and fix the sliding switches or replace them, currently nothing is active..... 2 Quote Link to comment Share on other sites More sharing options...
+slx Posted March 23, 2019 Author Share Posted March 23, 2019 clean and fix the sliding switches or replace them, currently nothing is active..... I'll try that for a start and will report back. As my car will be in the shop for a couple of days that probably won't happen before next weekend as I can't get to the electronics store to buy replacement switches. (And we always seem to have great weather on weekends, so I'll rather take the kids outside than tinker with old electronics indoors.) 3 Quote Link to comment Share on other sites More sharing options...
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