Old Computer Power Supply

like a lamp or a motor, if I can't get none of that, I will try with a resistor.

As mentioned above, the easiest thing to get in any town is a 12 volt auto tail light bulb. Connect it to the 5V and Ground. It will glow dimly and take 2 or 3 amps of current. I have used this on many PC power supplies.

josecoelho: Hi again, I found this when doing some more search: http://www.experts-exchange.com/Hardware/Components/A_3940-Use-a-Compaq-200-Watt-Power-Supply-PSU-as-a-second-power-source.html. I decided to try it and the PSU turns on, but after a few seconds, it turns off again.

I have Said it before, YOU MUST HAVE A MINIMUM LOAD AT THE FIVE VOLT OUTPUT. The fan are connected to the unregulated 12 V output. Perhaps if you connect the fan to the 5 volt output it will work, perhaps.

Pelle

If you read the info at the link I posted, there says that I need to connect something. I tried with a old hard drive and with a dc motor.

Perhaps you need an minimum load of 10 % of full load to make it work. 10 % of 200 W is 20 Watts. How many Watts did the DC motor consumed? And the hard drive?

Pelle

It shouldn't necessarily be 10%.

The problem is that if you have no load, the PSU may have difficulty not kicking the output voltage up so high that it may then detect an over-voltage (it is important that a switchmode power supply does have an over-voltage "crowbar") and shut itself down.

Hi, if you still have the old mother board that the supply was connected to, then reconnect it and use it as the load.

Tom...... :)

PS Just a random thought.

Hi! I have a PDP116P power supply as well and I’m trying to use it for testing and learning. When I plug the green wire to the white one and the grey wire to any brown one, it starts only for a second and stops… probably because there is no load as discussed earlier in the thread. I can use the motherboard as the load and it works, I tried it. But, is it possible to simulate the load of the motherboard?

@josecoelho : Do you have any updates on your side?

I use a 10K 10W resistor on the 5V line as shown in pic. It was convenient to cable tie it to the fan guard.

10K 10W small.jpg

JimboZA: I use a 10K 10W resistor on the 5V line as shown in pic. It was convenient to cable tie it to the fan guard.

You do mean a 10 ohm resistor, don't you?

Paul__B:

JimboZA: I use a 10K 10W resistor on the 5V line as shown in pic. It was convenient to cable tie it to the fan guard.

You do mean a 10 ohm resistor, don't you?

No. I used a 10K having read somewhere (no idea where, now... ) that that was the required one. I actually bought a 10R by mistake and then re-read the instructions and Lo! it said 10K so I went an got one and used it.

You’d hardly need a 10W resistor if it is 10k on 5V. The point is to draw about 500mA, hence 10 ohms on 5V is 500mA, 5V x .5A = 2.5W. 10W resistors are simpler to find than 5W and give you a bit more headroom.

polymorph: The point is to draw about 500mA

Well I just used the resistor that the article said: it (and all others I've seen) were silent on the current requirement to switch the supply on. So the info on the 500mA is good for future reference.

@JimboZA Check the next time you take the power supply apart as 10 ohms sounds like the correct value to me.

Could be your power supply had one already built in though.

LarryD: @JimboZA Could be your power supply had one already built in though.

Nope- it didn't fire up without it.

That's odd. I had to put a 10 ohm 5 watt on mine to get it to work.

LarryD: That's odd. I had to put a 10 ohm 5 watt on mine to get it to work.

I didn't try 10ohms, but yeah if it needs 500mA then 10K does seem waaaay too big. But it works....

(I do have a 10ohm one, so I might try it- it's just connected with terminal blocks so it's easy enough to swap out)

JimboZA: No. I used a 10K having read somewhere (no idea where, now... )

That would explain it. That ever-reliable source of knowledge. :astonished:

Oh thanks everybody for the answers! So I guess the best value for the resistor would be 10 Ohms 10W. But I'm wondering why the cd drive was not enough to start the power supply. For now, I use the power supply still connected to the motherboard XD but I will look for those resistors.

CD drives draw most of their power from the 12V rail. Only the low level logic uses the 5V rail, so if the drive isnt doing anything , like reading or writing it wont draw power from the 5V rail , which is what you need.

mauried: CD drives draw most of their power from the 12V rail. Only the low level logic uses the 5V rail, so if the drive isn't doing anything , like reading or writing, it wont draw power from the 5V rail , which is what you need.

Come to think of it, since as you say, the motors run from the 12V, it probably makes little difference to the logic current draw whether or not the drive is in fact reading or writing.