My trusty old Chieftec APS-650C decided to emit a pop and some smell few weeks ago. This happened when I pressed the power on button on the case.
Upon examination I discovered:
- No mains fuse blown, still drawing some little current from the mains
- TNY278PN MOSFET almost shorted (about 90 ohms drain to source)
- Primary of the 5VSB transformer open
- 470uF 400V TEAPO mains smoothing capacitor reading only 5nF
I managed to repair it. First I repaired the blown transformer, the tiny wire coming out of the winding to the pin on the transformer was blown. I was able to solder some new wire to it. Next, I replaced the TNY278, and the last, the 470uF 400V cap.
I cracked open the 470uF cap and one of the internal connections failed.
As I read from some foreign forums, this failure on these power supplies is quite common. The 470uF cap goes open, and then usually the TNY278 fails short which either blows the primary of the standby transformer or it blows the 0.22ohm resistor next to it. Sometimes it can also blow more stuff.
So if you are an owner of a PSU like this, and it still works, you better replace the 470uF 400V cap before it fails.
Upon examination I discovered:
- No mains fuse blown, still drawing some little current from the mains
- TNY278PN MOSFET almost shorted (about 90 ohms drain to source)
- Primary of the 5VSB transformer open
- 470uF 400V TEAPO mains smoothing capacitor reading only 5nF
I managed to repair it. First I repaired the blown transformer, the tiny wire coming out of the winding to the pin on the transformer was blown. I was able to solder some new wire to it. Next, I replaced the TNY278, and the last, the 470uF 400V cap.
I cracked open the 470uF cap and one of the internal connections failed.
As I read from some foreign forums, this failure on these power supplies is quite common. The 470uF cap goes open, and then usually the TNY278 fails short which either blows the primary of the standby transformer or it blows the 0.22ohm resistor next to it. Sometimes it can also blow more stuff.
So if you are an owner of a PSU like this, and it still works, you better replace the 470uF 400V cap before it fails.
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