:/ It's supposed to be an 'emitter follower' setup for current gain, for the fan(s), so why would changing the transistor change the voltage? Any help would be appreciated.

R1 is supposed to be 5k pot R2 is 100ohm R3 is 10k ohm C1 is 10uF C2 is 470uF Q1 is supposed to be BD243, I've got a 2SC1384 in it's place If I replace Q1 with a transistor I grabbed from a dead CFL (DD128F, can't find a datasheet for it), the fan speed is faster, but same problem of no control. The fan I tested it with has 4 blue LEDs and they just barely light up. Since this is a simple hub the fan speed you set up will be applied to all of the fans connected to this hub and will be seen as a single fan connected to your motherboard in your BIOS (this is how hubs work generally). My DMM has been dropped one too many times and now displays garbage unless I apply pressure on the LCD, so taking measurements is a pain in the ass, if I had to guess though, the voltage would be around ~2v across Fan+ and ground the pot is replaced with a 10k variable resistor right now. You can plug in up to 10 PWM fans (4 pins) and control them all using one single fan curve through your motherboard BIOS. Using to start basically I built the circuit on vero-board and tested it having just one fan powered, it spins at a slow speed, and turning pot makes no change.

Control pc fan speed