Another SX-64 problem for the group.

[Roy J. Tellason]

On Thursday 15 June 2006 09:43 pm, Ethan Dicks wrote:
> On 6/16/06, David Vohs <netsurfer_x1 at fastmailbox.net> wrote:
> > I have an SX-64 that has (apparently) a serious problem. On powerup it
> > shows nothing on the screen (checked the settings and and also hooked up
> > an external monitor) along with an occasional crackling sound from the
> > speaker. Keypresses are not registered by the machine.
> >
> > Anyone got any ideas as to what the problem could be?
>
> If the power supply is working (check for +5V at the corner of a TTL
> chip if you can't find it anywhere else, and see if you can see the
> glow of the CRT filament), the next thing to check is the PLA.  It's
> identical with the one in the C-64, so you can borrow one there.  If
> it's not either of those, you'll have to start chip-level debugging
> (unless you happen to have a C-64 diagnostic cartridge and cable
> harness, a tool sometimes used by C= dealers for debugging _mostly_
> dead machines).

I have that setup,  and it really doesn't do all that much,  and surely 
doesn't work on most all of the machines that I have encountered that gave 
the "blank screen" symptom.  We got it because we were a c= "factory service 
center" at the time.  I still have it someplace,  but have no idea where it 
is and am not too worried about finding it.  :-)

> If any of the DRAMs feel _really_ hot (too hot to keep your finger on),
> that's a symptom of fried RAM, an occasional cause of inertness.

Occasional?

> The ROMs are different from a C=64, but the only changes to the kernel
> are to remove the tape routines (no cassette connector), and change
> the default color scheme and startup message.

I have repaired SX-64s that needed a kernel rom by putting one for a c64 in 
there and it worked just fine,  with the main apparent difference being the 
screen colors as you mention.  I never took notice of the tape functions,  
though.

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