I have a pair of SX64's here, and would quite like to fix one (due to case
/ keyboard damage and only having one keyboard, it's probably only viable
to get one going)

Machine A shows signs of life - the disk drive light comes on and stays
on, with the drive spinning forever. The display shows an alternate
pattern of black and white pixels, apart from a run of about ten pixels in
the centre-bottom that are all black. Occasionally if I power it up I get
random cycling noises out of the speaker, and/or coloured garbage on the
screen.

Hitting reset shows no sign of doing anything.

+5V and +12V lines look good, and I've tried reseating all socketed chips
and checking cables. 


Machine B is totally dead - no sign of life whatsoever. Other than
checking the fuse I haven't done anything else, but before I spend hours
digging around in the PSU, is there a common fault with the power supplies
in these machines?


Any ideas? Oh, and just to be sure, I can expect a correct display without
a keyboard necessarily plugged in, right? (it's easier to work on the
bench without the keyboard getting in the way!). 

Of course I don't know the history of these machines. Someone could have
poured a bucket of water on them for all I know... (nor do I know anything
about CBM hardware)

cheers

Jules

On Sun, 18 Jul 2004, Jules wrote:

> Machine A shows signs of life - the disk drive light comes on and stays
> on, with the drive spinning forever. The display shows an alternate
> pattern of black and white pixels, apart from a run of about ten pixels in
> the centre-bottom that are all black. Occasionally if I power it up I get
> random cycling noises out of the speaker, and/or coloured garbage on the
> screen.
>
> Hitting reset shows no sign of doing anything.

 	Sounds like the PLA chip has died.  Ray Carlsen has just repaired 
two SX-64's for me, and both had the same problems and the same solution 
-- PLA replacement.

> Machine B is totally dead - no sign of life whatsoever. Other than
> checking the fuse I haven't done anything else, but before I spend hours
> digging around in the PSU, is there a common fault with the power supplies
> in these machines?

 	I can't help you with this one.  Raj Wurttemberg or Ray Carlsen 
would know better.

> Any ideas? Oh, and just to be sure, I can expect a correct display without
> a keyboard necessarily plugged in, right? (it's easier to work on the
> bench without the keyboard getting in the way!).

 	Yes, you don't need the keyboard for it to display (unlike a PC).

 					Truly,
 					Robert Bernardo
 					Fresno Commodore User Group
 					http://videocam.net.au/fcug