hueyjones70 Posted November 21, 2017 Share Posted November 21, 2017 I have an 800XL that powers on to a blank blue screen. The screen color can be changed with the color pot. I have swapped out the RAM,GTIA,ANTIC,and Sally. Anyone have any suggestions for further troubleshooting. Quote Link to comment Share on other sites More sharing options...
Rybags Posted November 21, 2017 Share Posted November 21, 2017 (edited) Is it entirely blue or just a blue window? What happens if you hold Option when turning on? Blue window only without "READY" probably means the Basic Rom is bad. Troubleshooting for that in order I'd suggest swap out Basic Rom, MMU, PIA. Edited November 21, 2017 by Rybags Quote Link to comment Share on other sites More sharing options...
SignGuy81 Posted November 21, 2017 Share Posted November 21, 2017 In case this could be same issue http://atariage.com/forums/topic/219536-trouble-shooting-an-atari-800-powers-up-to-blank-blue-screen/?hl=%2B800+%2Bblue+%2Bscreen&do=findComment&comment=3871121 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted November 21, 2017 Share Posted November 21, 2017 all blue edge to edge of monitor or blue like normal basic/memo pad/dos but without white text letters? Quote Link to comment Share on other sites More sharing options...
hueyjones70 Posted November 21, 2017 Author Share Posted November 21, 2017 All blue and inserting a cart has no effect. Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted November 21, 2017 Share Posted November 21, 2017 (edited) check power supply under load with voltmeter and capacitor near the power switch, as it sounds like the typical support chips and/or memory. check them next Edited November 21, 2017 by _The Doctor__ 1 Quote Link to comment Share on other sites More sharing options...
hueyjones70 Posted December 1, 2017 Author Share Posted December 1, 2017 (edited) The 800XL tech manual says to replace U2, that is a 74SL138 chip. Should I be able to use one from an 800 ROM. I check voltages on each pin on the chip in the blue screen computer and they were all significantly lower than the same voltages on the pins of a chip in a working computer. Edited December 1, 2017 by hueyjones70 1 Quote Link to comment Share on other sites More sharing options...
1050 Posted December 4, 2017 Share Posted December 4, 2017 Yes to using any other 74LS138 for testing purposes. Remove keyboard and try it without. SignGuy81's #3 might be the issue where SELECT and START are stuck on and you are looking at the Cassette boot screen. Which is waiting for you to press the spacebar IIRC, then it should beep to signal that you need to turn on the cassette player. Try swapping out 4051 chips before tearing apart the keyboard, they go bad often enough to be the real issue here too. Quote Link to comment Share on other sites More sharing options...
hueyjones70 Posted December 12, 2017 Author Share Posted December 12, 2017 I don't know if this is progress or not, I noticed that the OS ROM was getting very hot so I swapped it out with one that I know is good. Now I get a black screen. The computer doesn't seem to be making any effort to boot. Next I am going to test the BASIC chip and the MMU. Quote Link to comment Share on other sites More sharing options...
hueyjones70 Posted December 13, 2017 Author Share Posted December 13, 2017 The first thing I did was take the motherboard out of the computer. The keyboard was never an issue. Quote Link to comment Share on other sites More sharing options...
1050 Posted December 13, 2017 Share Posted December 13, 2017 Unless you've got some smutz on the keyboard jack around the area of pin 18 and higher and that errant drop of 25 year old soda is emulating SELECT and START for you without your knowledge. And you can't know that until you press the spacebar, and that circuit actually still works and only then does it go BEEP after a few seconds. Correction to my original proposition is that 4051 is not involved in SELECT or any other function button, that is GTIA's job but smutz on the motherboard top and/or bottom or damaged resistors or bent pins on bottom side might still be pressing a non-existent pair of buttons for you. Since GTIA has been changed it's unlikely that the fault is there. Standard working blue color is not the norm for a non-working machine. Can't ignore this so you really should plug in the keyboard and give the spacebar a press. Quote Link to comment Share on other sites More sharing options...
hueyjones70 Posted July 15, 2018 Author Share Posted July 15, 2018 800XL boots to a blank white screen, no border; carts boot OK. What is most likely culprit? Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 15, 2018 Share Posted July 15, 2018 800XL boots to a blank white screen, no border; carts boot OK. What is most likely culprit? Could be a bad MMU, could be an issue with the PIA .. when you say "carts boot OK," how many and what types did you try? Do you have any larger games or utilities like OSS carts that would exercise the bankswitching? Quote Link to comment Share on other sites More sharing options...
hueyjones70 Posted July 15, 2018 Author Share Posted July 15, 2018 Star raiders, pole position, tbis computer has standard memory. 1 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 15, 2018 Share Posted July 15, 2018 (edited) Star raiders, pole position, tbis computer has standard memory. Do you have something that uses more memory? Even a 16K cart might behave differently. If you have something like an UNO or Ultimate Cart, you could try a .CAR for Action! or MAC/65. They should work on any 48K or greater system. If those work okay, it would help eliminate the MMU, PIA and probably the OS from being the likely cause. Edited July 15, 2018 by DrVenkman Quote Link to comment Share on other sites More sharing options...
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