Dead Saturn. But not so dead.

Hi guys.
I'm the owner of two Sega Saturn units.
1 white japanese, HST-3220 and 1 black brazilian model 1, 21 pin, Tec toy model.

The black one boots up, but has a weak laser.

The white one is almost dead. It powers on, but doesn't show up anything, except for a black screen. Disc doesn't spin, laser doesn't move, no sound. Tried using another PSU, still nothing. No busted capacitors, just the goddamn black screen.

The casing has a hole in it, so I think it was caused by a failed mod attempt.
I really love the japanese one, so I'm thinking about getting spare parts from my other unit to save it.

What do you think it is, guys? Bad SDRAM? Bios Chip?

 

Check the bios along with any nearby traces.

 

Thank you for your answer.

Now that you said it, makes perfect sense to check bios chip. But how to make sure I have a defective one? By looking at, everything seems to be in order.

I do have some experience with electronics, but none with Saturn.
Do you have schematics for the VA SG mainboard?

 

Only one I know of is here http://assemblergames.com/l/threads/sega-saturn-schematics-for-va13-chassis-tec-toy.27654/ it should be somewhat useful, look for any kind of soldering in that area which doesn't look like factory done and also traces. I'm sure someone might have other suggestions for you.

 

Looked/tested the board inside out. No sign of damage at all.
Removed the BIOS chip, turned the machine on, and the machine is basically the same with/without it.

Looks like i have a defective BIOS. From what I understand, the machine doesn't know what to do without it, right?

 

x

 

Tested all caps. Every single one of them is fine.
Removal of BIOS chip made absolutely no difference, though.

 

That really doesn't tell you much beyond "it's not working" - anything that stopped the system from running the boot code would mean that removing the BIOS wouldn't make a difference.

I guess I would start by using basic electronic fault finding methods - make sure that all the power lines are present, the clocks are running and that the system isn't being held in reset. Electrically those VA SD / VA SG boards are still fairly close to the VA 0.5 boards, so you can use the schematics in the VA0.5 manual as a guide.

 

Yeah, you're right. I tried swapping bios chip with another Saturn board, no sign of life at all.
At this point, I'm thinking about SDRAM.

I'm gonna get new memories from a spare board and try to boot it.