Sega Naomi freezing after 30min play

Adrianlamande

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I am running wipi netdimm in an excellena (blue) with a TD-IO I built and while everthing is now working, I had to swap out the last Naomi 1 for another one to get it to work The last Naomi was playing OK for about 30min then it would freeze. You could reload a game and it would play for a bit but once it had frozen once it would keep doing it untill you tried again tomorrow. You would get 30 min and off we go again.

It's not voltage (getting 3.31v, 5.02v and 11.59v into the Naomi) and changing out for another working Naomi fixed the issue. Likewise it's not a netdimm or IO issue as they work perfectly on other Naomi boards. Fans are new, cooling is f No errors either.

This is not 1 board, I have a few that have displayed this issue over the years but as the cost used to be pretty low, I just got another one when this issue popped up. Now the price has risen a little, I am thinking it may be something worth fixing but it has me totally stumped. Anyone have any ideas what could be or where to look?
 
Lock up is not a normal thing for Naomi. Especially after 30 minutes. I could see it with one but more than one seems super odd. I am sole shop on planet repairing this platform and I have repaired thousands of them. Any lock ups outside of what you have described would be related to bad 27mhz crystal, bad RAM at SH4 processor, loose SH4 or Holley GPU. Maybe there could be issue with circuitry around RAM IC35. I am seeing this more and more now. Causes random weird issues.
 
Lock up is not a normal thing for Naomi. Especially after 30 minutes. I could see it with one but more than one seems super odd. I am sole shop on planet repairing this platform and I have repaired thousands of them. Any lock ups outside of what you have described would be related to bad 27mhz crystal, bad RAM at SH4 processor, loose SH4 or Holley GPU. Maybe there could be issue with circuitry around RAM IC35. I am seeing this more and more now. Causes random weird issues.
Thanks, I was actually hoping to get a response from @irepairsega, and this is exactly what i was looking for. A few may have been a bit of an exaggeration. I was just trying to avoid the typical, voltage, cooling, netdimm answers as this has been debugged pretty thoroughly. It's definitely 2 though, one recently and one a while ago. In looking for an answer I have also come across a few other examples, all of which did what I had done and replaced the Naomi.
They all seem to be early revision motherboards with the black heatsink, i have swapped in a late revision board with the Naomi 2 fan and heatsink. Both of mine that do it were some of the worst cigarette affected boards I have ever seen, which is why I initially suspected cooling but that path has been pretty much covered. I had deduced that it was likely a heat related voltage regulation or thermal expansion issue. I tried rebuilt original fans, swapped out to modified noctura fans, changed case, cleaned cases, (had previously cleaned mainboard) etc etc. I guess my next step is an inspection of the areas and components suggested under the scope for solder joints that could be causing issues, reflowing a few things and then looking at voltage and logic in those areas if that doesn't work.
 
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Thanks so much for pointing me in that direction. 1st one I examined under magnification had clearly had one pair of RAM that had been reworked. This immediately brought me hope I removed, cleaned and resoldered the pair that had been reworked and replaced the pair that looked to have original soldering and so far it has been running constantly for about 5hrs without freezing. The 2nd one was not as easy, I did the same thing to the RAM (cleaned and resoldered) but while maybe slightly better it still froze after about 30min. I then reflowed the CPU and GPU (not something I would typically try but an excuse to practice my hot air skills and if something went wrong I was already 1 Naomi up). while that seemed successful it didn't change anything. Checked voltages and logic at a number of locations but couldn't really find anything, then fed up I just replaced all the RAM around SH4 and 27mhz clock crystal. This one has been running about 1.5hrs without freezing now so I have my fingers crossed that has done it.
Thanks again, much appreciated.
 
I am sole shop on planet repairing this platform
I guess i`m living on another planet - sometimes i really do have this feeling. I have only few hundred units repaired, and about 150 owned. Nice to meet you, repair shop from Earth!
 
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