From: ray (raycomp_at_visi.com)
Date: 2006-11-06 16:59:48
On Nov 6, 2006, at 2:38 AM, Pasi Ojala wrote:
>
> - 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?
Have you checked the clock -is that running? (both the crystal and
the 7801 and on the Vic2)
Did you check that you have both 9 VAC and 5 VDC from the power
supply? Also check the voltage out from the bridge rectifier that
makes the +12 V from that 9VAC.
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|Raymond C. Bryan 651-642-9890 vox | The battle is sometimes |
|Raymond Computer 651-642-9891 fax | to the small
for |
|795 Raymond Ave -email: raycomp | the bigger they
are |
|St Paul MN 55114 _at_visi_dot_com | the harder they
fall. |
|USA Amiga - Commodore | -- James
Thurber -- |
http://www.raymondcomputer.com
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