I've just done two PSU to +12volt conversions. One was 180 watts ATX (Hewlet Packard) and the other 420 watts ATX (Raidmax). Following is a short description of what I did to each and the unique findings of each:
180 watts (Hewlet Packard) 15A on +12v rated
The wires on this one followed the instructions from here:
http://www.wikihow.com/Convert-a-Com...b-Power-Supply
The only exception was the brown wire which did not exist and did not find any other sense wires. I used the 10 watt 10 ohm resistor across the 5 volt rail and mounted it on the air vent grill with some thermal grease using regular twist ties through the grill. There were six yellow wires total and I soldered all six to a binding post and six black wires to another binding post. Everything else I didn't use I cut off so no wires were hanging out when I put the cover back on. Voltage read at 12. 27 volts with no load. I connected the Triton2, turned the psu back on and cranked up the charging amps to the highest setting. Triton2 said it was charging at about 20.5 v and 4.4 amps and my clamp meter said the Triton2 was drawing 9.4 amps from the psu. This confirms the 90 watt max of the Triton2. The source voltage read 11.04 v on the Triton2. However a quick check from the binding posts read 11.51 v under load. This psu appears to have plenty of power for the Triton2. I wonder why there is such a voltage drop from the banana plugs to what Triton2 two says it's getting? One other note, this psu did not power the Triton2 adequately under full load without the resistor.
Alright now the 420 watt (Raidmax) 13A on +12v rated
This one was a little more tricky and had me stumped for two days. Before I cut any connectors I tested the psu by jumpering the green to a black wire within the 20-pin connector and putting a 10 watt 10 ohm resistor across the 5 volt side of one of the molex connectors. The psu powered on and I had 12.18 v on the +12v rail. So it works. After I cut the connectors off and then regrouded the green wire and the resistor the psu would not power on. I got only the fan bump. Couldn't figure this one out until two days later I decided to count the wires which came from the 20pin connector. I thought well maybe there was a sense wire I missed but didn't find any brown wires. So I counted 21 wires in that bundle. Ha!! I went back the connector I had cut off and sure enough one pin had two wires in it. Both were orange but one was smaller gauge than the other. I connected these back together and the psu powered on. On this one I mounted the resistor on one of the aluminum heatsinks with thermal grease and twist ties. The rest of the conversion went according to the instructions. Voltage under full load from the Triton2 was 11.69 volts at the binding posts and Triton2 said it had 11.19 volts. So it appears this psu had slightly better voltage regulation.
What I learned from this:
- Soldering paste makes soldering a lot easier even when using rosin core solder
- After stripping the ends of the yellow or black wires and then twisting these ends together I learned that putting a dab of solder at the
base of the twist will hold the bundle together while you manuever them into position for soldering to the binding post.
- My "powerful" handheld spotlight only draws 3.8 amps from the psu at 11.8 volts.
- I tried the spotlight on the 5 volt side instead of the resistor and got nearly the same results as the resistor, except I was burning more watts with the spotlight than with the resistor.
- That sandbar resistor can become skin burning hot without a heat sink.