The fan on my VA1 (late model, NMB plastic fan) had been making clicking noises and a high pitched whine so i was set on replacing it. Some problems presented itself and the solution i ended up on didn't present itself by researching on the web. Upon research these facts presented itself: - Stock fan specs: 30x30x10mm, 5v, at 9000rpm (according to old datasheet) - The Console won't run without a fan tachometer signal - I could not find any 5v fans with the required tachometer signal (yellow wire) I ended up taking the route of getting power directly from the PSU and only connecting the tachometer line to the fan connector. The replacement i arrived at was a Sunon MC30101V2-G99 (30x30x10, 12v, tach line, 8000rpm). The Problem: The console won't accept a standard PC fan tachometer signal A VA1 Dreamcast will not run for more than a few seconds if it does not detect the fan spinning, this likely applies for VA2 units as well. It does not matter if you use a 5v or 12v fan, this problem persists. Research shows this Problem being fixed by using a 555 timer circuit that simulates a signal the console could handle, but in truth the solution seems to be much easier. When trying to measure fan speeds using a microcontroller you usually have to connect a pull-up resistor between 5v and the fans tachometer line, in the Dreamcast this resistor looks to be built into the standard fan. PC fans do not have the pull-up resistor built in. The Solution: Adding a pull-up resistor between 5v and the tachometer line By simply adding a 10k ohm resistor between the 5v and tachometer pins on the fan connector the console starts running without any issues as long as the fan is correctly wired up. For a 12v fan keep the resistor between 5v and tach Only move the red wire to 12v on PSU Be aware that i am by no means an expert in the field of electronics and that this information may not be entirely correct. The Aftermath: In the end replacing the fan got rid of the clicking bearing noise but once you close the top-case you still hear a high pitched noise. My assumption is that the design of the case somehow allows high frequency vibration to resonate. Running it at full speed this fan also moves significantly more air than the original and thus creates a lot of air flow related noise, once you reduce its speed the high frequency sounds become apparent. I may add pictures to illustrate all of this better, please excuse the messy formatting of the post. Any input on the matter is appreciated.