PSU power supply conversion problem

[123hotchef]

Ok i think this psu may be faulty too!

I have tried to make it into a bench supply but I can not get the unit to switch on.
It trys to start briefly for a millisecond but does not.
I have the 5V standby power working ok but thats as far as it goes.
I have tried dummy loading it too on the 3.3v 5v and 12v rails.

Any ideas people before i bin it!

model is hec-550td-pte

 

[123hotchef]

i followed this https://www.electronics-tutorials.ws/blog/convert-atx-psu-to-bench-supply.html

 

[123hotchef]

Here it is

 

[Parm]

I haven’t been following your previous thread, so apologies if I’m off the mark

However, if your trying to convert a computer PSU to work as a bench supply then have a look at rcgroups on the web.

I’ve successfully converted many IBM and HP PSUs to give 12 volts at upto 150 ams on some. It’s dead easy by just shorting out a few (specific) pins.

 

[123hotchef]

I haven’t been following your previous thread, so apologies if I’m off the mark

However, if your trying to convert a computer PSU to work as a bench supply then have a look at rcgroups on the web.

I’ve successfully converted many IBM and HP PSUs to give 12 volts at upto 150 ams on some. It’s dead easy by just shorting out a few (specific) pins.

cheers parm yeh i thought so too maybe this unit is faulty

 

[rikrobson]

Did you short the green wire. It needs shorting to one of the black ones

 

[graffian]

I alter the feedback circuit to make them work, there is plenty online about it.
I have done a few the only ones that I have failed to get working are laptop supplies, the protection kicks in and shuts them down.

 

[123hotchef]

Did you short the green wire. It needs shorting to one of the black ones

yes mate I even switched that wire

 

[123hotchef]

I alter the feedback circuit to make them work, there is plenty online about it.
I have done a few the only ones that I have failed to get working are laptop supplies, the protection kicks in and shuts them down.

what is the feed back circuit? the power ok one? (grey wire)
I even used 10w resistor for the dummy load no joy thats why i am thinking something is wrong with the PSU it makes a errr sound briefly before shutting down completely when switched on

 

[graffian]

The IC that controls the voltage looks at a voltage from a voltage divider, two resistors, that are between the 5v and 12v, this is all from memory I haven't done one
for some time. To alter them it's something like: snip the resistor off the 5V and add a resistor from the sensing pin of IC to ground. I only use the 12V.
You can add a pot and have the voltage adjustable. It's all online. I have pulled a few atx power supplies apart and you look for the IC and the
number, then find a drawing of how to mod that sort of ATX psu. Each one I have done I just copied what was online and it worked.

I can't get the voltage to go from 0 to 24 or 30V as some websites suggest, I get around 8 V to 16V, above or below that the protection circuit kicks in , I guess you need to alter the protection circuit, until someone does a website about it that's over my head.