My Sega NAOMI repairs thread

OldFoo · Post by **OldFoo** » Mon Sep 08, 2008 8:40 pm

I have 3 under my belt so far...

1 had a bad IC29

1 had a leaking cap and corroded trace on the EEPROM

1 had a bad RAMDAC

I found the bad IC29 by doing the self test, the leaking cap by looking closely at the board, the corroded trace by using a continuity test on my multimeter, and the RAMDAC by tracing the video back until I found where it stopped.

I would have to say that if someone sent me a NAOMI for repair I would look at it this way:

1. Check for a leaking memory backup capacitor. If found, check the traces on the EEPROM for connectivity to the Altera chip.

2. Power up the board.

3. If it comes up with NAOMI splash screen and no audio, run self tests to check RAM and reset the backup memory. Reboot it and the audio on the splash screen should be back. Replace any memory chips shown to be bad.

4. If there is no video or audio, check the EEPROM to Altera chip connections then check the BIOS. Look closely for physical damage to the board.

5. If it has audio but no video then check the RAMDAC to see if it has output. If it does then check the DC blocking caps and look for damaged traces on the vertical I/O board.

Beyond that you are getting deep in to troubleshooting.

Raymond

OldFoo · Post by **OldFoo** » Mon Sep 08, 2008 11:17 pm

thanks man! much appreciated the input!

OldFoo · Post by **OldFoo** » Tue Sep 30, 2008 2:32 am

this thread has saved me more then once. just wanted to add that this is awesome and helps out a lot.

Thanks :smt020

OldFoo · Post by **OldFoo** » Thu Dec 04, 2008 7:31 pm

channelmaniac wrote: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.

OK... This cart died again, but I think I found the problem. It's been on site and playing great for over a month with no more reocurrence.

Turns out it had a bad plated thru hole on the board. When pushing down on the plated thru hole with the voltmeter probe tip the board came back to life.

If you have a troublesome cart that isn't working and you've replaced the buffers on it, check those pesky platethrus.

RJ

OldFoo · Post by **OldFoo** » Mon Feb 09, 2009 7:52 pm

Just thought I would add a little something to the thread...

got hold of a error 22 dim card to fix for a friend...

The symptom was basically that it would randomly produce the error 22 after working for a while...reboot it works for a while again then the same...

Everything worked fine in my naomis and seemed like everything on the dimm checked out OK too...so connect dude's mobo and get the error just as described...checked the IO(good), re-seated boards, checked cables, etc, etc...all the usual stuff...no joy.

No bad parts on the dimm that I could find...so gotta be the mobo(?) I figured...but that's kind unusual for this error...

So, long story short, after banging my head against the wall for a while turns out the usb port was shot on the naomi mobo(literally if you thumped it while the dimm was working would produce the error 22 described)...replaced the port with one from a parts board and the error 22 went away...been working fine ever since.

Anyways, I just thought that was an odd fix for error 22 as it's the first time I saw the actual usb port on the naomi go bad like that where it kinda partially works but then (presumably) gets rattled loose from vibrations, etc. and errors out with a error 22...that's a first for me...And since I looked around and didn't locate that exact fix anywhere when I searched threads I thought I would throw it in here for posterity and such since this is a repairs thread after all.

OldFoo · Post by **OldFoo** » Mon Feb 09, 2009 8:24 pm

La4s wrote:Here you go.

Mouser Double USB Port

Thanks go-kun!

If you check this post by La4s you can find where to order a replacement USB port. I have a few in stock to use for repairs now.

RJ

OldFoo · Post by **OldFoo** » Wed May 13, 2009 2:55 pm

16 bit "buffers", well... bidirectional tranceivers, are part number: 74LCX16245MTDX

They are a TSSOP package, NOT the SSOP. The SSOP is too big to fit.

The are available from Mouser as well. I just replaced 6 of them on a stubborn Marvel vs. Capcom 2 cart. It would run fine at 5.0 volts but lock up at 5.15 before I replaced them.

OldFoo · Post by **OldFoo** » Wed May 13, 2009 4:07 pm

What do you think about my problem ?

http://www.sega-naomi.com/forum/viewtopic.php?t=2900

No sound, no display at boot with a cartridge of virtua fitgher 4

OldFoo · Post by **OldFoo** » Thu May 14, 2009 2:34 pm

youpla wrote:What do you think about my problem ?

http://www.sega-naomi.com/forum/viewtopic.php?t=2900

No sound, no display at boot with a cartridge of virtua fitgher 4

Hard to say without seeing it. Could be a short on the cart keeping one of the voltage sources down. May also be shorted buffer chips too.

Bent pins are a mother of a problem too as they could mess up the Naomi system too.

RJ

OldFoo · Post by **OldFoo** » Thu May 14, 2009 5:13 pm

Thanks a lot for your answer

Yesterday evenning, I struck gently on pcb of the cartdrige and I put it in naomi system. It had work !!

After played with one of my friend, we decided to change the game. When my friend came back his home, I tried again virtua figther but problem came back (no video, no sound, no boot from naomi 2 system)

Perhaps a bad weld ?