Fauly STfm keyboard

[fill-ST]

Hi all I am looking for a little help or pointer in connection to a problem I am having with a non responsive keyboard. Initially the keyboard was working but I re-soldered the mouse and keyboard ports as I was trying to eliminate a problem with a joystick not working. Since then a short blew the ps main fuse. The fuse was replaced and everything seemed ok, the ST boots up, sound and audio are fine, both LEDs on the keyboard are lighting but the mouse and joystick are not working and I can not control the cursor using the keyboard. So far I have replaced the keyboard C070122-002 chip but it made no difference. I also measured the voltage on the keyboard connector and got 0v on Pins 1,5,6,8 and have 5v on Pins 4 ,7. Pin 3 seems to be giving a reading of .13v

Has anybody had a similar issue or got any ideas where to look next.

Thanks in advance.

[DoG]

Do you have any other Atari you can test the keyboard on?

Otherwise the ACIA chip (MC6850) on the motherboard, that receives the signal from the keyboard, might be faulty.

[fill-ST]

Hi DoG, I will look into the ACIA chip. Unfortunately I don't have another Atari to test the keyboard on.

[DoG]

There is two MC6850 (ACIA) chip on the motherboard. Both is the same chip. One handles the MIDI and the other one handles the keyboard. So you could try and swap them with on and the other and see if that works first.

[fill-ST]

Just an update on my keyboard problem, It appears to be back working fine. I removed the floppy drive to check the MC6850 chip, I was planning to check if it was over heating while running but with the floppy drive out of position the keyboard, mouse and joystick all worked perfectly. I noticed the mounts for the floppy driver were broken and I think the drive may have been resting directly on the chip. So far so good :D . Thanks for your help DoG