Posted By
crock
on 2012-09-05
02:50:43
 |  Re: c16 doesnt work but screen isn't black
Sorry, I should have given you the code for the basic rom (318006-01.) Removing the kernal ROM (318004) will indeed give you a black screen.
As the screen and border have been set, and there has been an attempt to clear the screen the machine is starting the initialization but failing before it gets as far as displaying the start-up message. As such, it never gets as far as the basic ROM so that didn't prove anything.
Judging by the pattern on the screen, I think the most likely culprits are a partially failed RAM chip at position U6 or the address line multiplexer at U8. Unfortunately this will mean desoldering the old chip as neither is usually socketed.
I don't have many spare C16 ram chips but if you want to tackle this yourself, there is usually plenty on ebay (search for "TMS-4416"). The mux (74LS257) is also easily available.
Rob
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