Let me see if I can help you a little bit. I opened my Roku before I sent it back and looked at it. What I am saying is from memory and it is what I will do if the PSU fails again (I think).
Mechanical: There is plenty of room in the case. With the case open and the front nearest you, The power supply is on the left of the MB and connected to it with a 6 conductor cable. Removing the PSU involves removing the screws that hold the PSU to the bottom of the case (I think there are 4 or 6) and unplugging the PS cable from the MB. Easy, no risk. JUST BE SURE YOU HAVE REMOVED THE AC CORD FROM THE BACK OF THE UNIT. The connector to the MB may have a release catch. It is obvious.
Power Supplies and DC-DC converters: A typical ATX PC Power supply supplies multiple voltages, are big and bulky, start with AC and do the whole job. A DC-DC-converter takes in a DC voltage, lets say 12V, and produces several DC voltages. The one found by olllllo seems to be the right size and produces the right voltages at what appears to be the right or at least reasonable power levels. To use it we must be able to secure it to the inside of the case (Screws, Double Sided foam tape, etc). Just make sure that there is no contact between any exposed solder points on the bottom of the converter and the metal case. I like the two sided foam tape that comes in small sheets, 1" wide rolls or mini squares. It is often used to keeep pictures straight on a wall (at least at my house).
An ATX power supply has a "Power Supply ON" logic point. An ATX PS is always on to some degree if fed with input voltage. Pin 14 (green) is the "PS-ON" sense point. Tieing this point to logic ground will turn on the ATX power supply. This does not exist on the original Roku PSU as it is not an ATX PSU
Connecting to the 12V power supply: When you removed the existing PSU you left a nice rectangular hole in the back of the case. Get a small piece of plastic that overlaps the openeing in size. That gives you the wherewithall to drill some holes in the rear of the case around the opening to secure the plastic. Mount on the plastic in the middle so it sits in the opening, a small toggle switch (optional), a panel connector to fit the cable of the 12V (or whatever) brick that supplies the primary voltage. Radio shack has them. Wire the connector in series with the optional switch and wire (soldering probably required) to the DC-DC converter input terminals.
Connecting to the MB: The power cable (as I recall) has 6 wires. 2 Yellow, 1 Red, 3 Black) Wires of the same color are common and went to the same place on the PSU. Black is ground, I believe the red is 5 Volts, and the yellow was 3.3. That makes sense because the 3.3 volt supply has to provide much more power than the 5 volt supply so it needs heavier wire. You can use the old cable as it nicely gives you the correct connector for the MB. Just extend the wires with matching gauge and color (16 gauge should be more than enough) and connect them to the new DC-DC converter output.
Check your work, and before connecting to the MB make sure you have the right voltages at the right points.
The DC-DC converter should run very cool! the heat producing AC-DC part of the PSU is now outside the Roku case. If the DC-DC converter supplies 12V, you could even add a fan on the right side of the MB as there is room there also. Just have to add vent holes so the air has someplace to go if there aren't any. Fan is probably overkill as the major heat producer has just been removed
Hope that helps. This is not a major project nor is it a difficult one for a person with some electro-mechanical skills (ability to solder, drill holes, use tape, follow instructions, locate connection points, etc).
MAJOR DISCALIMER ABSOLVING ME OF ALL BLAME GOES HERE. PROCEED AT YOUR OWN RISK.
Last edited by barrygordon
on Fri Nov 11, 2005 10:43 am, edited 1 time in total.