From: Pasi Ojala (albert_at_cs.tut.fi)
Date: 2006-11-06 09:38:35
Hi all,
I've been working on a dead C128, and all socketed chips seem
to be working. I'm going to try logic analyzer next, but wanted
to ask if anyone can suggest something from the symptoms.
- Black screen
- Action replay inserted -> black screen
- CIA's, SID, VIC, VDC, MMU, ROM's do not cause failure in another C128
- Z80 seems to work, as the 128/64 mode goes low when C=
pressed during boot and stays high when not.
- When measured with a multimeter /NMI is low,
LORAM (P0) is low, P4-P5 may remain in input state.
(Does CIA2 even cause NMI's in normal boot operation?
Is this because the C128 autoboot checks for a drive?)
To me this seems to point to either 8502, PLA, or DRAM
(maybe less, because AR doesn't change things).
Probing the 8502 address and data lines should reveal more.
Any thoughts?
-Pasi
--
"As well try to understand the sun, Perrin. It simply is,
and it is not to be understood. You cannot live without it,
but it exacts a price. So with women."
-- Gaul in The Wheel of Time:"The Shadow Rising"
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