[sci.electronics] Need information regarding Nintendo system board

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