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Power supply

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BioniC187

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Hey guys, have a power supply for a freeagent external.

When the power supply used to work :
The power supply when plugged into the mains, and is not connected to the drive, used to hiss. If the power supply was connected to the mains, and connected to the drive as well, then no hiss noise.

Now this is the situation:

It recently fell on the floor, and stopped working. I opened it up, the wires on the inductor near the mains input of the circuit had wires broken, so i put them back in place.
I connected it to the mains, no hiss noise, even connected the drive, still no power to the drive.

Opened it again, checked the large capacitor and it was charged, at 160V and was discharging normally. Any ideas? What was the hiss noise i used to hear though?
 
What was the hiss noise i used to hear though?
Could have been the supply rapidly cycling on/off? With no load it would probably shut iself down, restart, shut down.......
 
The hiss could be from the power supply switching frequency dropping down into the audible range. Many switchers do that at light load because they skip pulses when they have no load.
 
Alright, thanks. Still no luck with getting this thing repaired :( i just don't want to pay lot's for a docking station or an enclosure, when i can attempt to repair this thing for free
 
Does anyone have a circuit for a power supply that outputs 9V and any amp rating, i would like to study it to check if i can get another powersupply, the lower powered ones (9V 0.4A) and convert it into giving more current. Possible?
 
to check if i can get another powersupply, the lower powered ones (9V 0.4A) and convert it into giving more current. Possible?
In general, no. Most consumer electronics is built as cheaply as possible and has no operating margin. So if you try to squeeze more current out either the volts will drop significantly or you'll let the magic smoke out.

BTW, have you checked the circuit board (under a magnifying glass) for a possibly fractured track?
 
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Hmmm, i have not, i have tested for continuity on the copper lines though and all is fine sadly. So i doubt there is a fracture. In a power adapater like this, what are the impact sensitive components, like the most likely to go first?
 
The heaviest parts, and their nearest neighbours, are the most likely to suffer.
 
Thanks alec_t for the hint on checking fracture, there was a minute fracture where a bit of solder was a broken away from the board, barely noticible, so i soldered him up, and everything is fine now :)
 
Glad it's working.
 
BioniC187 said:
Hey guys, have a power supply for a freeagent external.

When the power supply used to work :
The power supply when plugged into the mains, and is not connected to the drive, used to hiss. If the power supply was connected to the mains, and connected to the drive as well, then no hiss noise.

That may be normal. Many switching power supplies do very weird things if there is not a minimum load. Sometimes only one output is regulated and the others will be out of spec if the main output isn't loaded to a particular value.
 
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