Power source dead, all caps are good. What else?

[targeting]

I checked the big caps and they are ok, with a multimeter on 20ohm they all start from 0's to infinity sucking the power from the multimieter.

What can i do to indentify where is the problem?

I checked that it enters 230v on the plug and somewhere to the middle of the power source. But on the end it does not show the 12v....

it's the transformer?

the fuse is ok, shows 230v on the multimeter

[budm]

Re: Power source dead, all caps are good. What else?

What DC voltage do you get on that large main filter cap (black large cap) on the primary (hot) side? It can be just a bad start up cap (22~47uf/50v) on the primary side. Try heating up the caps with hair dryer to see if it will start up if you do have 325~335Vdc on the large cap.

[targeting]

Re: Power source dead, all caps are good. What else?

What DC voltage do you get on that large main filter cap (black large cap) on the primary (hot) side? It can be just a bad start up cap (22~47uf/50v) on the primary side. Try heating up the caps with hair dryer to see if it will start up if you do have 325~335Vdc on the large cap.

Voltage of that big cap is around 710v dc when the plug is on and no hair dryer. Didn't try heat it up either.

I measure the ins of the transformer and they say that to 710v around it... but on the outs it shows no voltage... but i could be measuring tthe wrong legs!

I am not very hardcore on electronics so go easy.

But i see from that you say is not, right?

[mariushm]

Re: Power source dead, all caps are good. What else?

710v isn't right. The large capacitor would explode with such voltage.

Are you sure the multimeter is working properly? Maybe the battery is low?

[targeting]

Re: Power source dead, all caps are good. What else?

710v isn't right. The large capacitor would explode with such voltage.

Are you sure the multimeter is working properly? Maybe the battery is low?

You are right, my bad. 710v is AC voltage that the caps shows.
On DC it shows +300v sometimes 400v.

Normal?

[mariushm]

Re: Power source dead, all caps are good. What else?

Still not right. 710v is not correct. The multimeter may have problems measuring AC voltage when there's a DC bias (the dc voltage) and therefore the measurement is useless.

The mains are 220-240v AC, and after the voltage is rectified you should get 310-350v DC, so that's what it should be on that large capacitor.

The capacitor itself should be rated for a maximum 450v, it would have that written on it. At over the specified voltage it would be damaged and explode or make lots of smokes.

OK, so I'm going to assume that you have DC voltage on the capacitor, and at proper levels. That only means everything before this capacitor is working fine (no fuse blown, no safety and filtering capacitors shorted and so on)

Next thing I would do is to check the TO-220 package screwed on the bottom heatsink, it's probably a mosfet so in that case you can use the diode measurement between gate, drain and source to see if it's blown or not. Make sure you pulled out the mains cable first.
If it is a mosfet there should be a resistor connected to the gate pin, make sure that one isn't shorted (resistance should measure something meaningful like 10-100-300 ohms etc, not 1 ohm or something small).
Check the diodes (I see two diodes there by the transformer) and resistors near that IC, make sure resistors aren't shorted, make sure the diode is working fine.

[targeting]

Re: Power source dead, all caps are good. What else?

Still not right. 710v is not correct. The multimeter may have problems measuring AC voltage when there's a DC bias (the dc voltage) and therefore the measurement is useless.

The mains are 220-240v AC, and after the voltage is rectified you should get 310-350v DC, so that's what it should be on that large capacitor.

The capacitor itself should be rated for a maximum 450v, it would have that written on it. At over the specified voltage it would be damaged and explode or make lots of smokes.

OK, so I'm going to assume that you have DC voltage on the capacitor, and at proper levels. That only means everything before this capacitor is working fine (no fuse blown, no safety and filtering capacitors shorted and so on)

Next thing I would do is to check the TO-220 package screwed on the bottom heatsink, it's probably a mosfet so in that case you can use the diode measurement between gate, drain and source to see if it's blown or not. Make sure you pulled out the mains cable first.
If it is a mosfet there should be a resistor connected to the gate pin, make sure that one isn't shorted (resistance should measure something meaningful like 10-100-300 ohms etc, not 1 ohm or something small).
Check the diodes (I see two diodes there by the transformer) and resistors near that IC, make sure resistors aren't shorted, make sure the diode is working fine.

That screwed on bottom heatsink on the 3 legs says numbers on diode measurement like (+lead on one legs and black on the other 2 says 500 and 700) so its working, right?

the 3 grey resistors 2 measuring ohm are around 100 dancing and other around 300 dancing.. but there is one that shows 0.01 or 0000. IS THIS THE ONE?

the diode...i see something wired to the midle legs of the 3 to220 like you say (dont know if it's the gate pin) it's shows on multimeter in 2000k ohm 099 and the other equal black close to a black cap shows 500.

Looking close to that grey resistor( the one close to the left of the botton rectifier?) she got the grey paint on bootoom somekind of pealed.... could be saying it's dead (burn) and this little piece?