Missin Slot on 4-Slot Board

My #4 slot is not recognizing any games. I've tried several games and I also put a game into it by itself. Nothing. I also readjusted the PSU to 5.3 and then to 5.04. The contacts on the board look good too. I'm also using a Razoola Bios. Any ideas out there?

Check the traces going to slot 4 and see if any are corroded or damaged. Also check the battery area for leakage.

NEgO MANIAC said:

I also readjusted the PSU to 5.3

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Not surprising you are having problems with it when you treat it like that. Are you getting a crosshatch on the screen?

Yes, I get the crosshatch. So what voltage should I be adjusting to? Usually just 5V is not enough for most pcbs.

Thats absolute crap. 5v is exactly what they're designed to be run at.

Increase the wiring. An absolute least of 4 wires of decent thickness should be used for 5v and ground.

Look up the datasheet for any of the 74 series IC's on your board while you're at it, taking note of the recommended supply voltage.

As for your problem, you want to find the 68000 pinouts which are available on the forums somewhere, and start following the address and data lines back from there. I suspect one of them is broken somewhere.

Edit: Sorry, ignore that last paragraph. I misread the post, thinking that no slots were working.

TTL/LS logic runs at +5v +/-5%, which = 4.75 to 5.25.

Set it to 5.1 at the board and be done with it. Some people have a fetish with setting it to +5.2v, but I wouldn't recommend that - especially in a Sega Naomi cab as that can fry buffer chips on the carts, DIMM boards, etc.

As for slot #4 not working:

Get a logic probe and check for signals on the address and data lines for the Program ROM/ROMs. Look carefully around slot 4 for corroded or gouged traces. Corroded traces are VERY common.

Just to the right of slot 1 is an area where the slot enable pin's signals are routed from the bottom to the top of the board. If there's gunk on the board that eats through the trace there you will have problems with one or more slots.

Look to the left and right of each slot. You'll notice that there are a few rows of chips that repeat in a pattern. These chips are dedicated to the slot they are near. Using that as a starting point you can use your digital mulitmeter (NOT ANALOG!!!!) on continuity to check for connections between the chips and the slot.

Compare the signals from the chips next to slot 3 and the pins on the cart slot to the same setup for slot 4. If you find a trace that doesn't have continuity then patch it with some 30ga Kynar wire - available at any Radio Shack.

If it's something that you can't tackle then there are folks on the forum that can fix it for you. I'm one of them.

RJ