Alternate SNES S/PDIF solder points

Started by Hojo_Norem, February 14, 2013, 07:11:03 AM

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Hojo_Norem

My main SNES died a few days ago so I decided to mod the backup.  After hearing a few tales of people having trouble soldering to those awkward pins on the DSP I decided to look for some better locations to solder to and I did.

My SNES (and most likely almost every one out there) has a DAC IC.  This IC must be fed from the same lines that we tap for the mod so after googling up the DAC's datasheet and metering out the connections between the DAC and DSP confirmed this was the case.  The DAC provides ILRCK, ISCLK and SDIN (using the terms on the wiki article).  Obviously +5v and GND can be had there also but I didn't use them (more on that later).  For the RESET and OMCK signals the nearby expansion connector provides them on pins 19 and 21 (and another convenient GND point).

IMO the DAC is far easier to solder to and I guess if you manage to kill it all you loose is sound and pretty much any 16 bit stereo DAC could replace it (with re-wiring of course  :P )

I've attached a (rather poor) pic of the mod in my replacement with the various pins highlighted:
A - Reset
B - Master Clock
C - Sample Clock
D - Sample Data
E - Left / Right Clock
Formerly 'butter_pat_head'

Lugus

What's your motherboard model, and what's your DAC?
I have a sns-cpu-gpm-02, and a IC "NEC D6376 9331CG", but it's next to multi out and RF. Is that the DAC you talking about?

Hojo_Norem

February 15, 2014, 04:27:19 AM #2 Last Edit: February 15, 2014, 04:34:12 AM by Hojo_Norem
Quote from: Lugus on February 14, 2014, 01:31:24 PM
What's your motherboard model, and what's your DAC?
I have a sns-cpu-gpm-02, and a IC "NEC D6376 9331CG", but it's next to multi out and RF. Is that the DAC you talking about?

In the case of your PCB rev. that is the DAC.  A search for 'NEC D6376' gets me the datasheet on the first hit.  A couple of minuets googling 'sns-cpu-gpm-02' get me a page that leads to a much easier to understand diagram:
UPD6376
NEC AUDIO 2-CHANNEL 16-BIT D/A CONVERTER

           +---+--+---+
4/8 fs SEL |1  +--+ 16| CLK
     D.GND |2       15| SI/LSI
        NC |3  uPD  14| LRSEL/RSI
     D.Vdd |4  6376 13| LRCK/WDCK
     A.GND |5       12| A.GND
     R.OUT |6       11| L.OUT
     A.Vdd |7       10| L.REF
     A.Vdd |8        9| R.REF
           +----------+

"SI/LSI" = SDIN
"LRCK/WDCK" = ILRCK
"CLK" = ISCLK

edit:  Looking at my dead SNES pcb, it has the same IC with it pointing away from the cart slot (pointing up in my picture above) so as long as you account for the direction of the IC on your PCB then you should be able to use the same pins as the ones I have marked.
Formerly 'butter_pat_head'

Lugus

February 19, 2014, 12:16:16 AM #3 Last Edit: February 19, 2014, 03:31:38 AM by Lugus
Thanks for the detailed confirmation, I get so insecure because I'm newbie in this mod stuff. With this shortcut, it'll be much easier to perform the mod. As soon I get my CS8405A from china, I'll try it. Thanks!