Sega naomi sun PSU won't power on under load

Jmari98

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To keep it brief, if I power up the cab with everything plugged in properly it won't work. If I unplug the Naomi, the psu will power right up, and if I plug the Naomi in seconds after it will run perfectly for hours with steady voltage.

My noob opinion is for some reason it's lacking the juice to safely power up to spec while under load so maybe it's a cap issue? No clue. Would love a more informed opinion. Thanks!
 
To keep it brief, if I power up the cab with everything plugged in properly it won't work. If I unplug the Naomi, the psu will power right up, and if I plug the Naomi in seconds after it will run perfectly for hours with steady voltage.

My noob opinion is for some reason it's lacking the juice to safely power up to spec while under load so maybe it's a cap issue? No clue. Would love a more informed opinion. Thanks!
Open up the PSU. If it is a cap issue there's chance you may be able to ID the bad cap. It's straight forward to recap one. I just did one a few months ago, but not because it was having this issue.
 
Open up the PSU. If it is a cap issue there's chance you may be able to ID the bad cap. It's straight forward to recap one. I just did one a few months ago, but not because it was having this issue.
Adjusted the voltages to where they're a bit under spec at the connector on the Naomi about 4.9 and 3.2 and it fired up... Not sure exactly why 5.0-5.15 wasn't acceptable and 3.3-3.45 didn't work but less did. Always heard naomis love that range. Never thought power starving it even slightly would change anything.

The voltages are steady and when it's on it works like a dream but start up has been odd for awhile. Not trusting this won't be an intermittent issue. Have another hiccup I probably will just go ahead and cap it.
 
Recap full clean and a new fan is a must with these SUN psus. Even if the voltage 'looks' stable if it's on original caps they let through too much AC and kill boards.
Good to know. I'll pop it open and give it a look over the weekend and see if it's looking good in there. I really should've already just really been dragging my feet on it 😆

Cab was restored before purchase so I haven't had much reason to do work on it other than a bit of monitor work with a connector/convergence.
 
Recap full clean and a new fan is a must with these SUN psus. Even if the voltage 'looks' stable if it's on original caps they let through too much AC and kill boards.
Yes I forgot to mention I also got a new fan. The old one spun, but much slower than it should. Good call
 
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