Hallo Bo, I repaired my very first VIC-20 by stopping the 6502 right on the start by negating RDY. I then found out that the ROM did not get an enable-signal. The next step was making a circuit that enabled me to let the 6502 run step by step. Then I attached LEDs to the lines. Etc., etc., etc.... Maybe an idea for you as well? Good hunting. Groetjes, Ruud Aan 23-01-00 20:04, in bericht <yam8057.27.137498976@mail.prismnet.com>, Bo Zimmerman <bo@zimmers.net> schreef: > Hello all. > > I spent a few hours this weekend playing with my P500, trying to figure out > why it is misbehaving. The symptom is that no video signal appears to be > forthcoming from the machine -- at least my PAL/NTSC converter is not > reporting a valid PAL signal from it, and blind disk commands give no > response. The machine could be completely dead, I don't know. > > I Have converted the power supply from 220V->110V using a spare B500 PS, and > that changed nothing. I've checked the EPROMs, and they are fine. I've > swapped some of the common chips (processor, etc), and thats no help. The > seller swore to me the thing worked when it left his house, so I am quite > confused. > > Today I checked the voltages on everything, and it looks cool for the most > part. I did discover something strange, however. There appears to be TWO > grounds. One that runs along the AC line (from the wall), and one that > runs along the DC line. I've never noticed this before and am wondering -- > is this normal? Is it good? > > I figured there might be someone more familiar with electrical stuff on > this list to help me out. > > I appreciate any replies on this matter though, > > - Bo Zimmerman > > - > This message was sent through the cbm-hackers mailing list. > To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi. > - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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