Yes the problem is in the PSU.I'm running a DC motor that draws around 5A max.
I can use the motor on 5V line without problems but as soon I plug it into the 12V line psu shuts down.Generally if I try to draw more than 10W from 12V it just shuts down.

Most power supplies only regulate the "main" output. The other lower power supplies then track that output. Try loading the 5 volt supply while your motor is plugged into the 12 volts. (This assumes that the 5 volts is the main output. There may be a 3.3 volt, or such, instead.)

A question: What is the 12 volts rated for? 10 watts may be all you can get.

 

Not in my dictionary. Please educate me.

phenomenon*

Ok... Before getting any 'deeper' please check C18 and C19

Best regards
HP

Will do!I already replaced C18 few months ago when PSU was functional so thats where problem may lay.

Most power supplies only regulate the "main" output. The other lower power supplies then track that output. Try loading the 5 volt supply while your motor is plugged into the 12 volts. (This assumes that the 5 volts is the main output. There may be a 3.3 volt, or such, instead.)

A question: What is the 12 volts rated for? 10 watts may be all you can get.

Well this PSU normally supplied 200W just for the GPU until it decided to go south.

Here are the specs:
3.3V/14A
5V/28A
12V/18A
-5V/0.5A
-12V/0.8A
+5VSB/2A

Im starting to think that this PSU is not repairable.

 

phenomenon*


Will do!


Well this PSU normally supplied 200W just for the GPU until it decided to go south.

Here are the specs:
3.3V/14A
5V/28A
12V/18A
-5V/0.5A
-12V/0.8A
+5VSB/2A

Im starting to think that this PSU is not repairable.

@RichardO may have it. Add some load to the +5 as well.
The other possibility is the start up current of the motor is to high. What is it's resistance at rest?

 

Well this PSU normally supplied 200W just for the GPU until it decided to go south.

Here are the specs:
3.3V/14A
5V/28A
12V/18A
-5V/0.5A
-12V/0.8A
+5VSB/2A

Im starting to think that this PSU is not repairable.

Since the supply worked with the motor on the 5-volt supply I would try loading it to at least 1 amp with the motor connected to the 12 volts.

 

I did try loading 5V with 50W load it caused 5V line to drop to 4.5V. If i loaded 12V and 5V at the same time PSU would shut down. I m gonna try loading 5V with motor and 50W load at the same time.

 

I did try loading 5V with 50W load it caused 5V line to drop to 4.5V. If i loaded 12V and 5V at the same time PSU would shut down.

And the motor resistance?

 

I did try loading 5V with 50W load it caused 5V line to drop to 4.5V. If i loaded 12V and 5V at the same time PSU would shut down.

That's curious inasmuch as the +12V rail is clearly a 'slave' -- Here's a 'crazy' thought -- I notice the cooling fan draws its power from +12V -- Could there be a problem there (i.e. an over-current fault in the fan)?

Best regards
HP

 

And the motor resistance?

FWIW -- The inappropriacy of electric motors as test loads was broached earlier in this thread - apparently the TS has eliminated same as the source of difficulty?

Inasmuch as electric motors exhibit significant starting currents I suggest a purely resistive test load...

Best regards
HP

 

FWIW -- Note also that 'forward-going' OV 'spikes' will often 'trigger' a shutdown...

 

And the motor resistance?

Motor resistance is around 1 ohm accordingly to the reading.Im testing the psu via 1.5 ohm resistor.

 

Motor resistance is around 1 ohm accordingly to the reading.Im testing the psu via 1.5 ohm resistor.

Nonetheless, a purely resistive test load would be more satisfactory...

Best regards
HP

 

Im just going to use a car battery charger and few caps to run the motor.Thanks for help everybody!

 

Im just going to use a car battery charger and few caps to run the motor.Thanks for help everybody!

I apologize that I failed to realize the motor was the intended load -- I thought it was merely an expedient test load --- Please be advised that operation of loads characterized by 'heavy' inrush currents and/or high levels of electrical noise (e.g. electric motors) from switch-mode PSUs is readily achievable via 'soft start' techniques and filters (Such an arrangement need be no more complex than an ICL varistor and a capacitor)...

Please let us know should you require further assistance

Best regards
HP

 

I would like to use my SMPS to run the motor but it seems that psu has too much dead caps which i cant detect without esr meter and I dont have all the proper values of caps to replace the damaged ones+ they made the pcb without any test points so its a nightmare to probe.

Im probably going to try soft start the motor but im pretty sure that its not going to work.1 out of 10 times PSU would work with the motor without problems so the issue is most likely a cap.

 

I would like to use my SMPS to run the motor but it seems that psu has too much dead caps which i cant detect without esr meter and I dont have all the proper values of caps to replace the damaged ones...

In my experience 'carpet re-caping' of electrolytics in 'wonky' PC PSUs (and their ilk) is the most productive approach --- The capacitance values aren't especially critical (-30% +80%)-- Of course each replacement cap should meet or exceed the original Cap's maximum WV rating...

Best regards and good luck!
HP

 

Just tries car battery charger.It works fine,motor draws like 1.5A when free running , when under load around 3A.

 

Just tries car battery charger.It works fine,motor draws like 1.5A when free running , when under load around 3A.

≈45 Watts? A rather 'light' load indeed!-- By way of satisfying my curiosity, might I inquire as to your application for the motor? Inquiring minds... And all that...

One caveat: LA (Lead Acid) battery chargers not uncommonly feature 'fancy tricks' (e.g. 'desulphation cycles' [i.e. pulses of up to 40V)], 'taper charge'/'topping up' [i.e. 'voltage triggered' dynamic current limiting], 'activation' [i.e. application of > 30V upon 'detection' of apparently 'open' loads]), etc. --- So... The less sophisticated the charger, the better for your purposes! --- Moreover, it is advisable to shunt the charger's output with at least 10mF (i.e. 10,000uf) 's worth of electrolytic caps -- rated to no less than 50 working Volts...

Very Best regards and, again, good luck!
HP

 

The motor will be for small CNC machine im building.Its going to be used to drill pcbs and hopefully its going to have enough power to engrave pcbs.But if it can drill aluminium heatsink it should be able to engrave pcb with small 0.1mm bit. I dont have 10mf cap only 4000uF 35V.

 

I have a few stepper motor driver modules, bought to make a DIY CNC machine. All of the installation manuals for the different manufacturers of them agree on one thing, a linear power supply is to be used. They highly recomend NOT using a switch mode power supply for driving stepper motors. Just a transformer, bridge rectifier and smoothing capacitor.

 

I dont have 10mf cap only 4000uF 35V.

Of course attainment of greater capacitance may be achieved via paralleling multiple capacitors --- Please be certain, however, that the maximum output EMF of the charger cannot exceed the MWV specification of any Cap...

Best regards
HP