Can I hazard a simpler guess?
Clean the cartrige port? Seems to me if it's dirty or something is shorting
a pin someplace in it it could be triggering the cartrige sense even when
there is no cartrige in it. Which would give you a system trying to come up
with no roms.
>
> >
> > OK - So it might not be strange to those experts in Commodore hardware, so
> > I hope one of them reads this!
> >
> > This was one of the few missing things in my CBM collection until yesterday.
> > The system first appeared dead, showing just a blank screen. But then it
> > worked fine with any of my assorted game cartridges in the cartridge slot.
> > To test the disk drive, I pulled out a cartridge-based spreadsheet which had
> > load and save commands and the disk drive worked OK.
> >
> > The big surprise was when I put in the Simons Basic cartridge and this heavy
> > old "portable" C64 came up with its normal opening screen "SX-64 Basic" etc
> > and it loaded and ran a variety of programs from disk without a problem. But
> > without a cartridge, or with a C64 Super Expander cartridge, just a blank
> > screen.
> >
> > Could it be a RAM chip that is faulty, with Simons Basic causing some
> > relocation of memory that allowed the system to work? Unfortunately, the
> > insides are not nearly as easy to get at compared to a standard C64.
>
> [I'm assuming this is somewhat similar to a C64]
>
> My first guess is that it's partial failure of the BASIC ROM. The Kernal
> is probably OK (since it can run from cartridge, run the disk drive,
> etc). Since, I suspect, Simons BASIC uses some of the routines in the
> BASIC ROM, I guess the ROM is partially OK, and that it's being selected
> correctly by the PLA.
>
> But if the initialisation code in the BASIC ROM was damaged, it'd not run
> BASIC if no cartridge was installed. Simons BASIC probably doesn't use
> this code.
>
> Second guess : The Kernal ROM is partially defective -- in particular the
> part that calls the BASIC ROM if no cartridge is installed.
>
> -tony
>
--
Jim Strickland
jim_at_DIESPAMMERSCUMcalico.litterbox.com
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Received on Sun Mar 11 2001 - 12:38:07 GMT