SEGA Saturn Sophia devkit - need help getting it to boot

Provided the SH2s are working fine, you'll need to play with the jumpers; one of them sets the machine to boot from CD instead of booting from VCD (it doesn't boot because it stalls waiting for response from the VCD part).

 

I'll post my exact issues in another thread to prevent hijacking this one any further! :wink-new:
I wonder if Headcrab has had any luck?

 

Here's one interesting difference I've noticed between a Japanese Sophia and a European Sophia. The European Sophia will not work with NTSC mode on and the Japanese Sophia will not work with PAL mode on. Make sure the NTSC / PAL switch on the front (SW1, #5) is set to whatever region the motherboard is labelled as. If you don't have that just stick 120V to NTSC and 240V to PAL and viola, you might get video.


Seems the circuitry is missing but could have been implemented, I see missing XTALs! I haven't compared the European board and Japanese boards side by side though.


Anyway, failing that replace five SMD capacitors around the 315-5746 chip and chances are you'll definitely maybe have video back. Damn mid-90s SMDs. I've done this on three Sophias that all had no video out. The 315-5746 chip is something to do with signal generation, bad caps in close proximity = loss of video.


Hope you haven't given up on this one!

 

The 315-5746 is the PLL. It generates the clocks used by the majority of system components. On normal Saturns anyway. I don't know how a Sophia is wired up. Check the XTALs next to that chip, one of them should be 14.318mhz on a NTSC machine and 17.732mhz (or so) on a PAL machine.
If those pal/ntsc switches affect the PLL pin 1, then the video output will fall out of sync.

 

Yep, there we go! Spot on, OSC1 is missing on the Japanese unit but present on the PAL units (17.734MHz) and XTAL3 is missing on the PAL but present on the Japanese unit (14.318MHz).

Edit: Strangely I was able to use NTSC mode on one of the "PAL" units. I don't know the science behind it... maybe it's the screen I was using. I was using a SONIQ, now I'm using my good old Samsung. Either way... cool beans!

 

Glad to have you back, by the way.

Will you do picture galleries of your other Sophia units? The one you did for the first machine is INCREDIBLE.

 

Thanks and certainly! When I do get around to replacing the remaining capacitors I'll be sure to snap a load of photos of every chip inside!
Not quite sure when though :\
Time seems to disappear...!

 

Oh hell yes, a success story finally! I've just ordered some new cables (the SCART went missing during my house move!) and I'll get straight to replacing those caps soon.

Glad yours is working! My interest in this has piqued again.