My Sega NAOMI repairs thread

OldFoo · Post by **OldFoo** » Sat Aug 09, 2008 3:04 am

OK,

Since I'm repairing a couple of NAOMI systems I thought I'd document them for the community.

Enjoy!

RJ

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Interesting system, this Naomi...

This one had a RAM error: IC29 and had a leaking memory backup capacitor.

I replaced the bad RAM and tested. System was then dead. Urg. Double checked my soldering, everything was good.

Removed the BIOS ROM socket, the serial EEPROM socket, and cleaned up the capacitor electrolyte. Tested the traces on the board that pass through the area affected by the electrolyte. Found a bad trace under the serial EEPROM.

Patched the trace and played a game of WWF Royal Rumble to test the system.

The serial EEPROM chip holds data for the Altera FPGA chip. The Altera chip could not load its data so the chip was not functioning as needed by the system. This resulted in a dead system. Once the EEPROM could be read the Altera chip's gates were properly configured for the system to operate.

OldFoo · Post by **OldFoo** » Sat Aug 09, 2008 3:12 am

This was actually the first NAOMI board I worked on.

A good customer sent me one that was labeled as "untested, broken USB connector" with the hopes I could fix it.

Replaced the noisy fan and USB jack.

The USB jack was tough to find. Desoldered the jack and took it to an area "computer junk store." Found a Pentium II board in their scrap bin that had the same jack. Desoldered and installed it on the NAOMI system.

Played a game of Marvel vs. Capcom 2 to test the system.

OldFoo · Post by **OldFoo** » Sat Aug 09, 2008 3:20 am

The same customer whose repair is listed above also sent me a Marvel vs. Capcom 2 cartridge that wouldn't boot.

Took the cartridge apart and found some nasty dirt/dust/cigarette tar mixture caked onto the chips under the vent hole area. Cleaned the board with alcohol and a toothbrush, rinsed with more alcohol, then thoroughly dried it.

Board booted and played great.

Note: You want a 99.9% ultra pure alcohol which works great for cleaning boards. Avoid most store bought alcohol as they are between 30 to 50% WATER and will not evaporate quickly.

OldFoo · Post by **OldFoo** » Sat Aug 09, 2008 3:28 am

Here you go.

Mouser Double USB Port

OldFoo · Post by **OldFoo** » Sat Aug 09, 2008 3:34 am

La4s wrote:Here you go.

Mouser Double USB Port

Thanks,

I just ordered 10 of 'em. Mouser is a great place just on the other side of the Metromess from me. Order with cheap shipping and still get it next day.

RJ

OldFoo · Post by **OldFoo** » Sat Aug 09, 2008 3:41 am

Yeah, I really like mouser. I ordered a few of these when I had to replace the usb port on one of my Naomis, and they shipped them to me in no time flat.

-La4s

OldFoo · Post by **OldFoo** » Tue Aug 19, 2008 4:11 am

AARRRRRGGGHH!

The RAMDAC in the Dreamcast is different than the one in the NAOMI.

Dreamcast: 315-6258

NAOMI: 315-6145

The 2 DACs have different pinouts for power/ground. Sux.

I have a NAOMI here with a dead RAMDAC. It'll blister your finger.

Unless a different source is found, the only source for a NAOMI would be another NAOMI. Urg... The DC is only good for fixing an AtomisWave as they use the same one.

RJ

OldFoo · Post by **OldFoo** » Sat Aug 30, 2008 4:45 am

Repaired: NAOMI 1

Symptom: No video, has audio

The startup sound worked but nothiing showed up on the monitor. Traced the circuit back to the RAMDAC which was VERY hot to the touch. (Blister hot)

Replaced the RAMDAC with one from a parts board and enjoyed a couple of games of WWF Royal Rumble.

OldFoo · Post by **OldFoo** » Sat Aug 30, 2008 4:49 am

Model: NAOMI 1

Symptom: Dead

Check traces between the Altera chip and the 8 pin EEPROM. If ANY bad traces are found then look closely at the solder joints on the memory capacitor for ANY sign of crusting, liquid, or even the green area of the board turning black. Remove the capacitor, clean the electrolyte off, patch the trace, and put a new memory capacitor on the board.

The EEPROM connects to the Altera chip like this:

Pin 1 - Pin 12

Pin 2 - Pin 1

Pin 3 - Pin 37

Pin 4 - Pin 4

Pin 5 - Ground

Pin 6 - Not Connected

Pin 7 - +5v

Pin 8 - +5v

OldFoo · Post by **OldFoo** » Mon Sep 08, 2008 7:11 pm

Hey...Just curious...what do you consider to be the most common problem parts to check first on naomi mobos(assuming a totally dead mobo with unknown cause)? Might save me the trouble of testing everything piece by piece on future repairs...thanks!