Atari 800XL - Need some tech help

[cx2k]

Working on an Atari 800XL for a friend. Here's the issue - holding down the OPTION key does not disable basic.

 

This is a stock 800XL, fully socketed. Keyboard is verified good.

 

I tried swapping the usual suspect chips at first, then went on to swap every chip on the board with a known good working board. No change.

Machine boots into Basic every time. Type "BYE" and go into self-test and keyboard tests good (including START, SELECT & OPTION).

Boot holding down START and you get the cassette boot noise.

Also, tried another good working keyboard. No change.

 

Any advice or suggestions before I pull my hair out?

 

Thanks!

 

 

[Beeblebrox]

Delete

Edited July 1 by Beeblebrox

[+DrVenkman]

Yep, check the OPTION key is working in the Self-Test. If it is being read correctly, that means GTIA is registering the keypress (GTIA reads the console keys, POKEY reads everything else). If GTIA is registering the keypress but you can’t boot without BASIC, that makes me think something is up with the PIA. Since chip-swapping didn’t seem to make a difference, check the socket for debris or broken/bent/corroded wipes (contacts). 

[videofx]

Go into basic and enter and run my program:

 

10 PRINT PEEK (53279)

20 GOTO 10

 

Now run it.

 

The number should change as you press the console keys. This way you will know if the keys are being recognized.

[cx2k]

8 hours ago, DrVenkman said:

Yep, check the OPTION key is working in the Self-Test. If it is being read correctly, that means GTIA is registering the keypress (GTIA reads the console keys, POKEY reads everything else). If GTIA is registering the keypress but you can’t boot without BASIC, that makes me think something is up with the PIA. Since chip-swapping didn’t seem to make a difference, check the socket for debris or broken/bent/corroded wipes (contacts). 

You nailed it. Double checked again and it was a bad PIA. I guess I got delirious changing all the chips and must of not tested after swapping PIA the first time. Thanks!

 

[StickJock]

21 hours ago, cx2k said:

Working on an Atari 800XL for a friend.

 

LOL.  "Asking for a friend."

 

[Mclaneinc]

30 minutes ago, StickJock said:

 

LOL.  "Asking for a friend."

 

Actually, that's how it normally works

 

There's no shame in admitting you have an Atari