On 03/02/2013 19:03, Gerrit Heitsch wrote: > > The luma pin needs a pullup to work. It will only sink current but not > supply it. The datasheet specifies a 500 Ohm pullup. The usual circuit > also contains a diode (1N4148 for example) between VIC and pullup. Hmm, I assume the pullup is in the modulator on this board. I just powered it on without the vic present and there's nothing pulling it up so that could be the problem. > >> What is the minimum requirements a VIC-II needs to generate a sync >> signal? > > It should do that once you supply power and clock. There will be no > picture, but the sync signals should be there. Can be easily seen if > you use a real CRT monitor. When you turn on an otherwise dead C64, > you still get a twitch from the monitor once it locks onto the sync > signal from VIC. I have a scope so I've been looking at the signal on the pin itself. > > Also, on the 250425: > > - +12V are present at Pin13 of the VIC? yep > - Clock signals are present (dot clock and color clock!)? yep, both > - Does the board contain any MOS-TTLs? (small ICs with MOS logo yes, it has a 7711 instead of a 74ls139, a 7712 instead of 74ls08 and 7708's instead of the dram mux's. Why do you ask? > and a 77xx number) > - Modulator has power? Even if you use the video out, the modulator > is needed to convert the video signals into Y/C and CVBS. > I have yet to open the modulator to find out. Certainly the unregulated 9v is there. Rob Message was sent through the cbm-hackers mailing listReceived on 2013-02-03 19:00:45
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