Got one of these analyzers and have been working to quiet it down, but I had a look around at some things which may be useful to others:
The fan monitoring is done by an FPGA under the CPU fan blower which overhangs from the main computer module - but it seems to be tolerant down to pretty low tachometer signals. I hooked up the signal gen to the two board's fan connectors and verified both to be happy down to at least 50Hz. The CPU fan is a 5V job, and the default blower is stupid loud... but what baffles me is that the computer module is designed to be run fanless (I suspect with some ambient circulation), so why throw in such a loud blower if anything?
The clearance from the board to the top cover of the module is around 35mm, so it's not easy to get a regular fan to blow across the fins, so what I opted to do was to get a 12V rated 60x60x15mm fan and mount it on the opposite side of the fan module attached to the top plate (three new screw holes, but easy to do and plenty of clearance to keep the intake from being obstructed). Since there's space for a small hard drive there, it's unpopulated with the CF card for the OS and is open space. At 5V instead of 12, this blower is quite quiet, and still manages about 70Hz on the tachometer signal.
The PSU I'm running into the same problem for, as best I can tell, it's the primary source of noise now. I tried swapping in a fan rated for 4500rpm and it still wasn't happy, and yeah there's no tachometer signal from the PSU, just the alarm signal, so you'd have to find a similar RPM fan or spoof it somehow. I looked around for settings for what's required in terms of RPM in the software, but it's all done in the FPGA it seems like, and with a hex editor I can see a command prompt call following the fan stopped error message to allow a shutdown to be called by the program, but not the shutdown call itself. And really, I don't want to stop the thing from monitoring the fans altogether, I'd like to know if one fails legitimately too.
Anyways, for some other notes about the instrument:
The basic CF card is 50x speed, moving to a 140x or so card was a notable load time improvement
The processor board is an SOM-4470F with a 700MHz Pentium 3 and 512MB of PC133 RAM installed (but only running a 100MHz FSB). It's designed to run fanless, so should be just fine with the ventilation for the card, and it's an ETX form factor board, so there's some chance a different board could be used (though with the FPGA interface and the various outputs mapped to the bottom connectors, it could be difficult to find a match, I don't know the spec.) As it's a soldered on chip and a maxed amount of RAM, there's no upgrades to be had here.
Fan 1 is the CPU heatsink fan
Fan 2 is the computer module ventilation fan
Fan 3 is the 120mm rear fan
Fan 4 is the PSU fan
It appears that Fan 3 does not send a tachometer signal back to the computer module, it could be monitored on the board it connects to and then sent back as an alarm signal like with the PSU.
PAX.exe is the main screen you see in the operating system and it handles all of the rebooting from the fan monitoring, so closing it prevents the reboots if you're tinkering with the fans. I was unable to see exactly how the FPGA talks to the program, the device manager is not installed, but it seems to be a parallel interface from the routing on the board, and using a terminal to monitor COM1 yields no results.
Most of the directories are hidden if you access the CF module on a different computer (you just have to check view hidden files in explorer on the instrument itself), but the important ones are C:\Advantest\R3477 where factory calibration information is along with some other stuff and C:\Program Files\Advantest\R3477 is where the application itself is, as well as text error logs. For me, there's one more, C:\FIDTSERV , because that seems to be where the touchscreen recalibration software is.
I've got a replacement screen and touchscreen coming for my unit, but otherwise it seems happy. Had to replace the lithium battery on the CPU board for it to keep time, but it seems to be a real solid instrument and I'm looking forward to having it around.