Mac128, since you mentioned the required analog board voltage adjustment after adding a fan, I thought it best to mention one more thing. The fan in my HyperDrive 512 also passes it's power wires through a filter, as shown in this photo. EMI filters and chokes are technically not required, but if you see "snow" on your CRT after adding a fan, you will need to add such filters to clean it up. As a result of having these filters (which are external and separate from the secondary PSU that accompanies the HyperDrive), there is no on screen noise when the Hyperdrive and cooling fan are running. The screen is just as clean as my other Mac512 which is stock (no fan, no hard drive).