We powered up our system and found a noise coming from the Power distribution block. We disconnected all of the other components to isolate the noise and yes it is coming from the power distribution block. It almost sounds like a fan that has some material rubbing against it. A steady high pitched whine. Any thoughts?
Read the Power Distribution datasheet. A whine from one of the boost supplies (24v to the cRIO and 12v to the WGA) is normal.
Just out of curiosity, why do electronics make that noise sometimes?
Thanks,
Boost Buck supplies use high frequency switching voltage into an inductor or transformer. If the frequency should get low enough, sub harmonics of the switching frequency become audible. In some cases, the core of the inductor or transformer actually vibrate and you may be hearing that as well. Most transformers and inductors are manuufactured with a little glue or varnish to keep this to a minimum. The hard knocks of competition may break this bond. A search of this forum will give you some other references to the noise from the design team.
To convert DC voltages, you turn it into Alternating Current, then use a transformer to change (bring up in the 24 volt case) the voltage, after which you turn it back into Direct Current.
Lower frequency AC requires larger transformers. To maintain efficiency and keep costs down, these circuits typically operate at several kilohertz - that is what you are hearing, the kilohertz frequency acting upon some circuit element.
The whine from the motor when you use a victor at partial power is a similar concept.
Don
ohhh… so that’s how you get 24VDC from a 12VDC source. I’ve been thinking about that for a while…hahah 
Thanks!
For more information, look at page 10/11 of the schematic for the PD, found at http://usfirst.org/community/frc/content.aspx?id=11838
Long story short, the left half of the page tells Q13 (a MOSFET transistor) to turn on and off rapidly.
When the transistor is conducting, current flows through the inductor to ground, building up the energy in the inductor. When it shuts off, current goes through the diode into the capacitor, using the energy in the inductor.
Don’t worry, energy is conserved. 