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Re: MEGA ST 4 - blank screen boot
Posted: 01 Jun 2026 09:44
by PhilC
@macsonny then your reset circuit is fine.
Re: MEGA ST 4 - blank screen boot
Posted: 01 Jun 2026 11:13
by macsonny
PhilC wrote: 01 Jun 2026 09:44
@macsonny then your reset circuit is fine.
So could it be the MC68901 chip?
Re: MEGA ST 4 - blank screen boot
Posted: 01 Jun 2026 11:47
by PhilC
macsonny wrote: 01 Jun 2026 11:13
PhilC wrote: 01 Jun 2026 09:44
@macsonny then your reset circuit is fine.
So could it be the MC68901 chip?
It could be a lot of things, including dirty or damaged sockets, bad ram chips. Glue mmu etc
Re: MEGA ST 4 - blank screen boot
Posted: 01 Jun 2026 12:25
by macsonny
PhilC wrote: 01 Jun 2026 11:47
macsonny wrote: 01 Jun 2026 11:13
So could it be the MC68901 chip?
It could be a lot of things, including dirty or damaged sockets, bad ram chips. Glue mmu etc
I thought bad RAM showed up as a white screen with a black border?
Re: MEGA ST 4 - blank screen boot
Posted: 01 Jun 2026 12:43
by rubber_jonnie
Typically no RAM shows as a black screen with a white border. bad RAM may show up as on screen corruption dependent on where the bad RAM is.
A fully white screen generally means a ROM issue.
However I would add that these rules are not 100% set in stone, though they are generally sound.