atari 800 dead -> green screen

[Marius]

Hi.

 

I'm not so familiar with Atari 800...

 

I bought one today, but now it appears to be dead. (Green screen).

 

I already cleaned contacts on RAM and OS card.

 

What is the first thing to check when the Atari gives a green screen?

 

Greetz

M.

[candle]

74ls243 & 74ls42 i guess

Edited March 6, 2012 by candle

[Osbo]

This thread might help you,

 

http://www.atariage.com/forums/topic/177258-atari-800xl-nothing-on-screen/page__st__25

 

Good luck!

[Marius]

Thanks for your replies guys. Today I found out that the LS09 on the installed OS-Rom board was dead. Replacing it resulted in a working Atari 800.

 

Still ... this machine is not error free (strange enough). When I switch it on it seeks for Sio hardware (the famous prrrr) but it won't boot from my ABBUC-RAF Sio2USB although that thing gets enough power from the sio port.

 

Strange issues on this computer.

 

It is NTSC btw. It gives a very ugly output on my television (a lot of noise and artifacting) although I use my monitor cable which I also use for my 800XL.

 

I also have a NTSC 1200XL which gives a much better screen output using the same cable and tv.

 

My PAL 800 also gives a perfect screen output through this cable.

 

Is it a common thing that NTSC 800 screen output is worse, or do I have to look further for improving things?

[Pug]

Where is the LS09 CHIP? Is it a socketed chip? Thanks in advance!

[+DrVenkman]

7 minutes ago, Pug said:

Where is the LS09 CHIP? Is it a socketed chip? Thanks in advance!

That's one of the logic chips on the 800 OS board - a 74LS09 (full designation). That said, a number of things can cause an 800 to fail to boot like this - most common is bad RAM or a bad OS ROM chip. Anyway, the 74LS09 is the socketed chip at bottom-center, just above the card edge connector.