(ask) SMPS ATX PROBLEM

[miftah]

I have a problem with atx psu .This does not
work well .green wire is connected to
ground .the purple cable 5V measurable .the
fan is not running ..what causes it ? please
help...

 

[KatieandDad]

Are you trying to repair a PSU in a computer or use it for something else ?

 

[miftah]

I will use for psu amplifiers .I have 2 ATX psu will i series to get 24v 20A .but that is a problem .. please help

 

[KatieandDad]

Try disconnecting the Power ON (Green) from ground and just touching it to ground with the PSU ON.

 

[miftah]

it still does not work .whether VSB gets voltage from the transformer secondary ?.if yes means I check which part ?

 

[ballpencil]

1. PS_ON (usually green wire) has to be connected to Ground.
2. There has to be a minimum load for the ATX PSU to turn on. Try putting 10 ohm / 5 watt resistor across +5v and Ground. Be careful, this resistor will be very hot.

 

[miftah]

An externally hosted image should be here but it was not working when we last tested it.

this is schematic is very identical to my psu. i cant get voltage at big transformer. at pin vcc of tl494 there 12v and to vsb i get 5v.. whats wrong?

 

[ishiru]

some SMPS wouldn't work without any load tied to them like ballpencil said.

 

[miftah]

some SMPS wouldn't work without any load tied to them like ballpencil said.

I 've put RL 2 .2ohm /5watt .and jumper the green wire to ground .but it still does not work .

 

[KatieandDad]

Do these PSUs work when fitted to a computer ?

 

[ishiru]

does the PSU shared the same ground?.

you intended to use them to produce 24V, right?.
it means the + side of 2nd PSU would be connected to - side of 1st PSU.
take a look on the grounding.if both of them were connected, the PSU would see it as short and they went off.

 

[miftah]

does the PSU shared the same ground?.

you intended to use them to produce 24V, right?.
it means the + side of 2nd PSU would be connected to - side of 1st PSU.
take a look on the grounding.if both of them were connected, the PSU would see it as short and they went off.

yupz... .but that's my new plan .I would disconnect the ground to the chassis to avoid short .I have two psu .and the other one works fine .I just got this from my friend , but this does not seem to work well. maybe I have not been lucky hehehe