#### Binary Buddha

Joined Sep 24, 2016
40
Project Reference: http://www.instructables.com/id/Variable-ATX-bench-powersupply-FabLab-edition/?ALLSTEPS
Power Supply: Thermaltake TR2 600W

So, I'm trying to use the stated power supply in the referenced project. I'm just short of setting up the actual connectors and variable supply circuit. I stopped to test that the power supply wouldn't blow up or catch on fire. I setup the "Power Good" (PG) light and the "Power On" (PO) switch. I setup the dummy load on ATX pins 19(+5V) & 17(GND) from the 20 pin connector using a 10 Ohm resistor.

When I powered it; with caution, the resistor heated up to a glowing red and burned through the heat shrink. I posted a pic of it below.

After re-reading the reference material, the author stated to use the +5V as it has it's highest current. So, just using any +5V with a 10 Ohm resistor won't work I'm assuming. The point behind the resistor is to provide a dummy load to trick the power supply into thinking it's connected to a running motherboard. After check the specs on my power supply my +12V1 pin has the highest MAX current rating of 23A.

So, my question is ... How do I find the minimum load for +12V1?

This site states that 1A is general rule of thumb. While this site says 2A.

Would it be safe to say that calculating for 4A and using a 3 Ohm resistor connecting +12V1 to one of the GND wires would work?

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#### Dodgydave

Joined Jun 22, 2012
8,295
All the atx psus i have modified, i use a 10 ohms,so on the 5V rail @ 10 ohms is 500mA, you need a 10Watt resistor at minimum for safety .

#### Binary Buddha

Joined Sep 24, 2016
40
All the atx psus i have modified, i use a 10 ohms,so on the 5V rail @ 10 ohms is 500mA, you need a 10Watt resistor at minimum for safety .
So 14 Ohm resistor?

#### Dodgydave

Joined Jun 22, 2012
8,295
If you like, 14ohms then on the 12v rail.

#### Binary Buddha

Joined Sep 24, 2016
40
So, I burnt through more resistors. Any idea why? I didn't have a 14 Ohm; so I used a 10 and 3.9 ish. Ignore the crappy job. It's just a test setup.

#### Binary Buddha

Joined Sep 24, 2016
40
And your derpy derp moment of the day... Wrong type of resistor... it works now.

#### AlbertHall

Joined Jun 4, 2014
8,189
I didn't have a 14 Ohm; so I used a 10 and 3.9 ish.
Because you didn't take note of the power rating required for the resistor. 5V across 14Ω is nearly 2W and most of that would be in your 10Ω resistor. As DodgyDave said:

so on the 5V rail @ 10 ohms is 500mA, you need a 10Watt resistor at minimum for safety
[EDIT] But I see you've worked that out now.