Really hoping you can help me get to the bottom of this one. I am helping a friend get his saturn looking nice. It was working fine but had a scouple switches in the back for a region mod. It was an old mod for 1998 and so I planned to update it to a switchless mod. The old mod had daisy chained a couple crystals together for the switching and it was pretty ugly inside so I removed all that, fitted a new PAL crystal and replaced the jumpers with solder bridges to check all worked OK before I fit the region mod. Now it powers up and spins the disc up fine, but I don't get any picture of sound on the screen. The channel switches so the TV knows something is on there, but it's just a black screen. I am not sure what I have missed, but probably something obvious.
I grabbed a few pics of the board. As you can see I prepped the board for the switchless mod but didn't yet connect it. I have checked vdp2 pin 79 is grounded and set all the jumpers to what I believe the stock PAL config should be. The pics are at the following link:
It's not necessary to probe the video output, the console is locked up before it even goes that far.
I see a broken trace around JP6 (above the label on the board). I don't see where it leads to since it goes under the silk screen, and the other part of the trace goes under the chip. You'll have to do continuity checks to find wherever the signal leads to. If both sides of the trace end up under ICs, you can use thin single-strand wire soldered into the vias to repair it.
Thanks for looking at this for me. I think that was just a bit of old flux rather than a broken trace. I have buzzed it out and it turns out to be SSHRES line coming from IC2 pin 122 and going to IC9 pin 58.
I don't think there should be any broken traces as it worked before I removed the mod wires, and they just went to X2, and jp1, jp2, jp6, jp10 and jp12. So I have either screwed something up royally (hoping that isn't the case) or I have maybe missed something else they changed doing the mod.
I have done a bit more probing to check voltages. I was wondering if one of the chips was being held in reset when it shouldn't be. I believe all reset lines are active low. I checked IC1 which had a high state, IC2 which had an low state but I think that should be correct when in the language select menu, I also checked sysres that feeds VDP1 and VDP2 and this was also in a high state. So I think all of the chips in their correct states.
My next guess is maybe something going on with VDP2. If I can't come up with anything on VDP2 it looks like I'll have to try reflowing all the ICs.
IC2 is the slave SH2 and it isn't active all the time (in fact it spends a lot of time idle). Not sure if that's controlled with the reset line on the hardware level.
I think you should consider undoing whatever mods you set up, including the FRAM one. But before you do that, you say you switched out the main crystal - do you know if the crystal is working fine? If it doesn't, that could be the problem.
edit: and if you are already replacing ICs, consider installing a region free bios, then the entire switchless mod will become moot, you'll only need a 50/60 switch (which in reality you'll rarely touch unless you have a sizeable PAL library).
Unfortunately, it was all rather obvious. I am a fool. Of course it had to be something I had done, and other than removing the original mod I had also fitted the FRAM. I removed the +5V connection to see if the unpowered chip would change the situation but it was the same, so I just whipped the whole chip back off the board and it booted up no issue.
So FRAM chip was causing a strange issue for some reason. So glad I figured that out, and thanks for all your help with this one. Now to just figure out why it was causing the issue and how to fix it.