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[Repair Log] Sega Naomi

Hello! I recently acquired an "untested" Naomi 1 motherboard. I swapped the filter board it came with as it was pretty corroded and had some sketchy looking components.
I also swapped the super cap and bios. The case fan was kaputt so I pulled it out for now.
Board looks good otherwise, like it was made yesterday, but it won't show a picture on any of my monitors, just static interferance. There is a boot sound however so it's not completely dead.

I've previously managed to save a couple of laptops by heating the motherboard in an oven (wrapped in aluminum foil and only exposing the gpu chip) so thought I'd try the same procedure on the Naomi and see if it comes back alive. Have anyone tried this?
 
Alex_P said:
Hello! I recently acquired an "untested" Naomi 1 motherboard. I swapped the filter board it came with as it was pretty corroded and had some sketchy looking components.
I also swapped the super cap and bios. The case fan was kaputt so I pulled it out for now.
Board looks good otherwise, like it was made yesterday, but it won't show a picture on any of my monitors, just static interferance. There is a boot sound however so it's not completely dead.

I've previously managed to save a couple of laptops by heating the motherboard in an oven (wrapped in aluminum foil and only exposing the gpu chip) so thought I'd try the same procedure on the Naomi and see if it comes back alive. Have anyone tried this?
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Check the 315-6145 , is it hot? Also make sure the video sync hasn't blown on the filter board. (video sync or ground, forgot which).
 
Hi,

anybody got a spare Ramdac? The one in my N1 is "blistering" hot and the screen flashes for a millisecond and then I have a black one. Can hear sound tho.
 
Got hold of a Naomi 1 for cheap, didnt expect it to work but enjoy a challenge!:

Powering on it shows 1 vertical bar - guessing its a GPU issue?

So far:
  • Supercap was replaced as it had leaked, I checked traces and continuity from BIOS to Altera, all good.
  • Replaced BIOS with multibios
  • (Annoyingly) recapped the entire board - lots of caps leaked, no obvious trace or board damage.
  • Tried swapping filter board from working system, no difference.
Power etc... all good as working on Naomi 2 netboot system.

Any ideas?
 

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I think a BGA problem or ram dac failure due to to high voltage . Naomi is to cheap working ....

to have it repaired makes no sense just chuck it in the bin :-)
 
Mine with dead ramdac looked almost the same on 15khz setting. Replacing it made it fully working again. Is there sound?
 
Casselfornia said:
Mine with dead ramdac looked almost the same on 15khz setting. Replacing it made it fully working again. Is there sound?
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There was no sound, I didnt have a cart or dimm installed but guessing it should still play a sound during the Naomi logo sequence.

Might switch out the ramdac just to check, this was on 15khz as well.
 
CoolFox said:
Check the 315-6145 , is it hot? Also make sure the video sync hasn't blown on the filter board. (video sync or ground, forgot which).
Click to expand...
thank you for your answer. the project has been on halt for a while but i now decided i should take another look at it..
filter board checks out. not sure about the ramdac, but i have a replacement im going to try to rule that possibility out..

few other things i noticed on closer inspection:

a capacitor is missing here.. do you think i can just bridge the connection?
IMG_20210202_182746.jpg


I could not get a reading from these resistors.. what are they supposed to be?
IMG_20210202_182814.jpg



Also, are these two resistors supposed to be soldered like this or have they moved? I'm afraid now I might have more components missing..
IMG_20210202_181838.jpg
 
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Touch the 315-6145 and tell us if it's hot. According to your description it sound very much like it has blown.

I wouldn't bother with the other stuff before checking that. Sorry. That sounded meaner than it was meant to be. ;)
 
Casselfornia said:
Touch the 315-6145 and tell us if it's hot. According to your description it sound very much like it has blown.

I wouldn't bother with the other stuff before checking that. Sorry. That sounded meaner than it was meant to be. ;)
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Alright I will try to replace the 315-6145, it did feel a bit toasty.. thank you :D
 
If it immediately after turning on gets hot, it's definitely toast. Replaced 3 of them in the last few months and it was always the same. Any idea where some can source the chips? You're welcome alex!
 
Casselfornia said:
If it immediately after turning on gets hot, it's definitely toast. Replaced 3 of them in the last few months and it was always the same. Any idea where some can source the chips? You're welcome alex!
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I don't own a thermometer so it's hard to tell, but it's replaced now :D Just need to clean up, check for continuity and hope that I don't have to redo it.. half of the pins are probably shorting..
found the replacement chip on ebay, around 10€ something with shipping

any clue about the PC19 capacitor? the first one to the left underneath IC9?
or do you know where one can find a schematic diagram?
 
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or maybe the cap isn't that important?.. I get an image now at least and ram test shows everything good :thumbup:
Ran in to a problem with my netdimm though. the naomi can only start with one dimm stick in the slot.. so i probably need to get a better psu?
 
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Ha, told you. Got no thermometer as well but it immediately got hot when u turned it on.

Maybe the cap is the issue. I got my Naomi's in the cabs and I am too lazy too take em out and disassemble them. Maybe I'll do it this week. I haven't found any schematics mate, sorry.

As long as you won't try to run melty blood it should be good I guess? Are you running it in a cab or as an external setup?
 
Casselfornia said:
Ha, told you. Got no thermometer as well but it immediately got hot when u turned it on.

Maybe the cap is the issue. I got my Naomi's in the cabs and I am too lazy too take em out and disassemble them. Maybe I'll do it this week. I haven't found any schematics mate, sorry.

As long as you won't try to run melty blood it should be good I guess? Are you running it in a cab or as an external setup?
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seems to be quite a common issue. it didn't get hot immediately for me, but then again I've burnt my fingertips many times before so maybe it's just me who doesn't feel it :D

I was also thinking maybe it doesn't like that a cap is missing, but it passes the ram test so idk. guess i have to try and dig around some more for those schematics.. or maybe desolder PC22 and measure it..

I'm running the setup externally, the psu I have is a thermaltake smart 630w.
cabinets are pretty rare here so the plans are to eventually frankenstein my own cab from bits and pieces. mostly looking for a 2p control panel, maybe some frame for the monitor, the rest I'll do in plywood or mdf.. But that's a project for the future :)
 
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nem said:
No, they're not. I have tons and they're all for sale.
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Maybe you own them all :D I think I've actually never seen a candy cab in person, only racers and various old jamma cabinets. How much do naomi cabs typically go for?
 
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well the new cap is in now.. I measured 115nF from the next capacitor.. probably wouldn't have made any difference if i just bridged the pads but it's there now lol

IMG_20210208_162234.jpg


Anyway, I tried powering the naomi with a pico psu I have and the netdimm works with both sticks in. dimm test also says good :thumbup:
But I also noticed alot of static noise on the display that I didn't see before with the thermaltake psu, so I think I'm gonna have to take a break and get a proper psu and a tester.. before I have to swap the ramdac again..
 
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