Select-able wall wart power supply - dead

[ben7]

Re: Select-able wall wart power supply - dead

Better off getting new PS, and unplug it when not in used.

Yes, and also overloading can cause it to burn out. Also, poorly designed transformers might burn out earlier too.

[budm]

Re: Select-able wall wart power supply - dead

Check the primary winding for open circuits, and if it has primary fuse, check that too.

[ajsemtb]

Re: Select-able wall wart power supply - dead

So for anyone rise in the future reading this thread, is there a faster way that I could have found this out sooner? I don't mind, I was taking it apart for fun. but for a problem like this, What is the process of diagnosing the failed parts on one of these?

[budm]

Re: Select-able wall wart power supply - dead

Better off getting new PS, and unplug it when not in used.

[ajsemtb]

Re: Select-able wall wart power supply - dead

Yeah, so dead transformer? Is it cheaper to just buy another ps or get the transformer?

[budm]

Re: Select-able wall wart power supply - dead

If you always leave this wall-wart plugged into the outlet, that power supply would have been running 24/7, so it will exposed to any surges/spike/over voltage/under voltage all day long.

[ajsemtb]

Re: Select-able wall wart power supply - dead

Oh and diodes are good.

[ajsemtb]

Re: Select-able wall wart power supply - dead

Ac prongs are open. No tone on continuity test open ohm reading. However all prongs that come off the bottom of it are shorted. They all have continuity which I would Imagine is bad... lol

[budm]

Re: Select-able wall wart power supply - dead

The two black wires on the left of the picture #2 which should go to the AC prongs are the primary winding.
If it is open, there should be a thermal fuse under that red tape on the transformer.

[ajsemtb]

Re: Select-able wall wart power supply - dead

There are about 7 wires that come off this transformer. Which 2 are the primary pair?

[ben7]

Re: Select-able wall wart power supply - dead

Check the resistance of the primary winding of the transformer, if it is O/C then the transformer is dead (has overheated)

[Evil Lurker]

Re: Select-able wall wart power supply - dead

What you say it is quite possible,but:all that ends with a wire melted because too much curent flown from it and so it is open, not shorted..

[Joun]

Re: Select-able wall wart power supply - dead

Actually it is quite possible. All it takes is two microscopic damaged areas of the magnet wire's insulation in close enough proximity to each other to create an arc. The heat from the arc melts other winding's insulation creating a chain reaction.

What you say it is quite possible,but:all that ends with a wire melted because too much curent flown from it and so it is open, not shorted..

[rogfanther]

Re: Select-able wall wart power supply - dead

Ajsemtb,

Disconnect the diodes. Then measure the AC output of the transformer. The series lamp is a good trick to prevent problems if there is a short.
If you get AC voltages from the transformer, your problems lie in the rectifier circuit, or even in the switch. Voltages probably would be 2V or 3V bigger than the voltages one can select from the switch.

[Evil Lurker]

Re: Select-able wall wart power supply - dead

I wouldn't trust that capacitor. Even with this being a linear power supply.

I wouldn't trust that PSU either. I would at least have a linear voltage regulator on the output, ultrafast rectifier diodes (supposedly they do improve sound quality), and full compliment of x-y caps and common mode choke on the input for no other reason to keep line noise out.

[Evil Lurker]

Re: Select-able wall wart power supply - dead

It is difficult if not impossible for the transformer (or any kind of coil) to be shorted..
How can a piece of wire "jump" and short phase with neutral? It is possible for two or three turns of the winding to short but that wouldn't produce enough current to light any bulb in series..

Actually it is quite possible. All it takes is two microscopic damaged areas of the magnet wire's insulation in close enough proximity to each other to create an arc. The heat from the arc melts other winding's insulation creating a chain reaction.

[Shocker]

Re: Select-able wall wart power supply - dead

I wouldn't trust that capacitor. Even with this being a linear power supply.

[Joun]

Re: Select-able wall wart power supply - dead

It is difficult if not impossible for the transformer (or any kind of coil) to be shorted..
How can a piece of wire "jump" and short phase with neutral? It is possible for two or three turns of the winding to short but that wouldn't produce enough current to light any bulb in series..

[Evil Lurker]

Re: Select-able wall wart power supply - dead

You can also put a 60w 120v light bulb in series with the transformer.. if its shorted the bulb should light up.

[vinceroger69]

Re: Select-able wall wart power supply - dead

i would unsolder one leg of each diode and re test them