The Sega NAOMI is a wonderfully versatile, reliable arcade board that, for collectors, is a lot like a more modern Neo Geo MVS. There’s LOADS of games and they are quite readily available. There’s also loads of them out there so spares are never a problem (at the moment).
Something that *IS* an issue though, by design, is the noise these things make, When new they are loud but that’s drowned out by their operating environment being loud too. As they ag, the bearings on the fans start to wear and the holes get clogged with dust they get even louder. In a home or quiet arcade environment the whine these boards make is horrible. So with this, and my sanity, in mind I set out to try and minimise the noise through a combination of CLEANING and NON DESTRICTIVE modding.
This is what we have to start with… A perfectly functional but VERY loud NAOMI 1 unit with, judging by the stickers, quite a bit of history.
So, these NAOMIs are loud because of one thing. Fan noise. There are two main fans in a NAOMI board. One on the mainboard and one acting as an exhaust vent sucking air over both sides of the PCB and out of the unit. This is in the top right of the pictre below.
These fans both get gunked up over years of use and a fan with gunk can become unbalanced and make more noise. Its also less efficient at pushing air and, if speed is temp controlled, will therefore spin faster (note that these are 3 pin fans so i DON’T think this is the case for the NAOMI, it’s full speed all the time). If the heatsink is clogged this can also affect the tone of the fan (backpressure). So, first up, looking at the mainboard fan.
Honestly, I’ve seen worse but this could use a clean to ensure it doens’t die early. The main source of noise on Naomi boards is from the exhaust fan (see later). Time to take the board out of the case. A few screws, disconnecting a fan cable and it just pulls out.
This leaves us with the underside of the case the the system exhaust fan (shown below). This think makes nearly all of the noise and it’s all due to a design decision that’s fine for an arcade, less so for home use!
Zooming in a little closer on the fan. This is a 60mm, high speed unit that is slotted directly on to a plastic vent that is simply placed into a groove on the under tray and then the top cover fits over. There’s no solid mounting for the vent and no damping or pressure on the fan mounts so, when running, the fan causes a lot of vibration to transfer to the case (ratteling in the groove between the cover and the undertray as well as ratteling on it’s mounting pegs). On a new fan it’s loud, on an older fan its really loud and has a horrible tone to it. This is the area I want to do something to in order to damp out this vibration, keeping it quiet and, importantly, keeping the board as stock as possible.
Before I did that though I did general maintenance on the rest of the board just to ensure it can keep running for years to come without having to open it up again. Taking the fan off the mainboardshowed suprisingly little gunk on the heatsink. This was cleaned off with cotton buds.
Next, checking around the BIOS on the board to ensure correctly seated and no dirt on the pins. It was fine so moving on to the BIOS battery. A standard CR2032 cell that holds the settings for the system. This was replaced with a new cell as I had no idea how old the installed one was.
A quick check on the back of the board…. Clean, no issues I can see.
Time to address the exhaust fan noise. If the fan is run outside the case then it’s actually quite quiet. To me this means the bulk of the noise is from the fan vibrating on it’s mounts and in the undertray slot. When it’s in place the fan is held ‘quite’ tightly in place but it makes physical contact with the top and bottom of the case and is pushed on to it’s hard platsic mounts via compression. So, first off, help damp the noise made by compression on to the mounting pins. As below, i’ve added a rubber band to act as a kind of gasket / vibration absorber to (hopefully) stop this vent plate ratteling as much (by both stopping the transfer of vibrations and by ensureing there’s more pressure on the plate stopping it from moving in its mount.
Next, I noted the contact points on the undertray and the top cover and followed the same principals as above by simply placing a rubber band around the center of the fan as this is the area that contacts the case plastic. NOTE: There isn’t that much clearance when re-assembled and the band has to be medium thick at max. When all put back together this band should halp damp the top and bottom vibrations.
Placing everything back together was actually trickier than I thought. There’s not a lot of tollerance in the mount when slotted in to the case. I had to twist the front rubber band on its edge to enable everything to fit back together. However, this does seem to have had the benifit of stopping any front – back wobble and also gives more damping surface area for the fan pin mounts.
Everything was now put back together and the case was given a good clean before hand with cleaning spray and isopropyl aochol (which is great at getting rid of sticker residue.
The board and case are now shiny and looking good. and the internals don’t have anything on them that could cause a failure in the future. As for the noise. It is WAY better. The sound is now akin to a PC CPU fan undrr load. you can still hear a whoosh of air noise and a slight hum but there’s now iregular vibration, ratteling or anything. Critically, with this in a cab you can’t hear it in normal gameplay. this was NOT the case before (where you really had to have the volume up high to drown out the fan).
For me, this is a success. The board is mechanically stock and can be returened to factore clean in minutes but it’s also playable in a home / quiet environment. WIN!