Is the SNES and N64 rgb wiring different?

Started by Drewman21, October 10, 2006, 09:55:33 am

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Drewman21

So I wired up a snes rgb cable to run into my rgb to component adapter.  Works great. I then tried it with my N64 that i wired for RGB and i get nothing. I have the one with the needed chip.  It is a usa ntsc model and i followed the diagram for the wiring to the letter.  I though after tapping the video chip the rest of the wiring would match the SNES's pin out.  
It works just fine back on the SNES so any ideas why it doesn't work?  

Drewman21

Ok, I tried tapping the chip from the back side and still nothing.  Does the N64 have c-sync or do i need to use the composite signal and strip it with a lm1881 chip?

viletim!

I dodn't remember there being a composite sync signal available from the N64's DAC.

Drewman21

So i'm boned unless i tap off of the composite video and strip it?  Would the standard LM1881 be fine?  I guess i will take a shot at it and see what happens.  Weird though about not seeing anything about the no composite sync on the wiki or the mmmonkey site.  I'll post up on the wiki what i find.  
Thanks Tim i was going nuts about getting this to work.

viletim!

I had quick a look at my n64 and yup, there's no sync at the connector. There's a pic marked S on the A/V connector though...so I followed the trace from it. There a bunch of missing components on the PCB which are meant to buffer the sync signal. These are missing on my board. Here's the missing sync buffer circuit:
.            Vcc
.           --+--
.             |
.           |/c
.  --R16-+--|   Q1
.        |  |\e NPN        
.        |    |                
.       R15   +--R14-+---o /CSYNC
.        |    |      |
.        |    R1    C22
.        |    |      |
.       -+----+------+-
.       GND

There's a good composite sync signal availabe at the input (R16) so maybe you can take the signal straight from there. It's unbuffered so treat it gently.

An LM1881 on the video or luma line would also work ok.