kenl@telxon (Ken K. Lambach) (12/14/90)
My brother-in-law recently gave me two Nintendo units which did not work. I have managed to repair one by replacing the capacitor on the modulator board. However, I am having trouble getting the second unit to work. This unit was 'dropped'. I have been ohming out the board and comparing it to the one which works. All appears the same (I don't have an oscilloscope to actually compare signals). I have noticed, however, that what appears to be the data pins (21-28 on the CPU) are not toggling on the dead unit like they do on the working one. Does anyone on the net have any knowledge of the system board or the CPU and PPU the Nintendo actually uses ? Does anyone know the manufacturer and chip number of the CPU and PPU ? Barring this information, does anyone know the full pinout of the CPU (I only know about half of the signals)? The symptoms of the dead unit are: The unit does not send anything to the TV through the modulator, although the TV screen does go gray (B&W TV) when connected through the modulator. I also connected this unit to my VCR through the audio and video connectors with no luck. The voltages appear to be OK everywhere (including the modulator board). I have been able to determine which CPU signals are the address lines. The lower 8 lines (A0-A7) are always low, while the upper 8 lines (A8-A15) give readings on my analog multi-meter somewhere between 0 and 5V, which indicates they are working. These readings are taken directly from the CPU. If the CPU is really a 6502 core should it not try to fetch a vector from FFFC and FFFD on reset ? Please email me as our news feed is sometimes erratic. I will post a summary to the net if there is sufficient interest. Thanks in advance for any and all pointers. * Ken Lambach * Telxon Corp Akron, Ohio * uunet!telxon!kenl