On Tue, Jul 19, 2016 at 1:09 PM, Ville Laustela <ville.laustela@gmail.com> wrote: > ... I did switch the power on and off and I did see the whole screen filled with random characters. Right. > Then it goes blank (just as it should) Right. > but then it goes to the blank screen with the single reversed ? on screen. It’s always on the same spot Can you tell where on the screen it is? Is it where the first "*" or "#" in the banner goes? > and also I noticed that the random characters were identical every time. If this helps any. The random characters are the power-on state of the video RAM (2114 SRAM chips in most PETs, 6550s in the oldest ones). Identical random chars are common/usual. Based on what I recall the reset code doing, it clears the screen early in the sequence of events, sets up zero page and other variables, then initializes BASIC and prints the banner. I would suspect you have a bad ROM or RAM to cause that sequence to fail before it can get the banner out. There are other causes, but those are common ones. Any of the techniques mentioned in this thread that clip on or plug into the 6502 socket and do not depend on RAM and ROM working (Fluke 9010/A, CBM diagnostic clip, etc) can help pinpoint what's really broken. -ethan Message was sent through the cbm-hackers mailing listReceived on 2016-07-19 18:02:08
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