[solved] recycling devices : capacitors discharge

[paul18fr]

Dear All

I've the opportunity to canibalize an electronic device destinated to recycling (see picture); Of course I'm interested by the housing, heatsinks and even the mosfets, the transformers (230V to ?, and so on.

I'll probably have to take care when I'll desolder some components to not damage them , but I've a question about the capacitors (please keep in mind I'm a newbie): I probably have to discharge them before handling them, don't I ?

What's the procedure ?

Thanks

Paul

[Simon]

The only capacitor you are likely to need to discharge is the one in the top right corner which is the power input capacitor and could have up to 300 volts on it. A quick check with a multimeter would be a good idea. Everything else should be low voltage. If you do try to discharge a capacitor try to do it through a low value resistor so as to not stress it.

Left-hand board is a power supply you might actually want to keep it in one piece as it will have many different output voltages which will likely include 3.3 V, 5 V, and 12 V.

The power supply is a switch mode type therefore the transformer is not a 240V to say 12 V transformer as you would normally use. This transformer is designed to work at a high frequency than the mains 50 Hz with the specific components on the board and won't be of any use to you for anything else unless you are very good at designing switch mode power supplies which given your experience I doubt.

[wiss]

the transformers (230V to ?, and so on.

That is not a 230V/50Hz trafo, more like 300V/50kHz.

[paul18fr]

The only capacitor you are likely to need to discharge is the one in the top right corner which is the power input capacitor and could have up to 300 volts on it.

the biggest one I suppose ...

If you do try to discharge a capacitor try to do it through a low value resistor so as to not stress it.

thanks for the trick ...

Left-hand board is a power supply you might actually want to keep it in one piece as it will have many different output voltages which will likely include 3.3 V, 5 V, and 12 V.

you're absolutly right; on the pcb one can read different output voltages

• +3.3V @ 1.5A
  + 5.0 VSB @ 0.3A ... what means VSD ?
  + 5.0V @ 2.0A
  +5.7V @ 1.2A
  +12V @ 0.7A

output voltages has to be probably tested with a multimeter on the ribbon cable (ground somewhre out ... first idea) ....
I've the twin of the device (but I've to perform tests to verify if they still work) ... in any way, good idea

The power supply is a switch mode type therefore the transformer is not a 240V to say 12 V transformer as you would normally use. This transformer is designed to work at a high frequency than the mains 50 Hz with the specific components on the board and won't be of any use to you for anything else unless you are very good at designing switch mode power supplies which given your experience I doubt.

you're right .... I'll keep the other PCB's with its components ... one day ... who knows....

[paul18fr]

the transformers (230V to ?, and so on.

That is not a 230V/50Hz trafo, more like 300V/50kHz.

On the PCB one can read: input voltage 230V / 50Hz ; that corresponds to the voltage of the power outlets

[Simon]

That will be the power input from the mains. The mains power is rectified and smooth with that big capacitor so you have about 300 V DC. Then that 300 V DC is converted back into high-frequency A/C which runs a transformer which is why it is so small.

[paul18fr]

I'll have many things to learn ... I'm not able to identidy the rectifier ...

[SeanB]

5VSB is a standby 5V power rail, which is always present when mains is applied. The other rails are switched on and off by transistors under control via a pin in the cable, so you will have to photograph the underside of the main board near the power inlet to be able to check which is the power control pin.

Just be aware that when mains is applied to this power supply around half of the board is at mains potential, so do not touch it at all, and keep the insulating sheet under it and the plastic stand offs it had.  As well only use it on an insulated sheet, to prevent shorts.

The rectifier is the black block at the top of photo next to the choke ( the thing with windings between 2 dull blue capacitors) just under the mains input connector. Right of the blue capacitor.

[wiss]

I'll have many things to learn ... I'm not able to identidy the rectifier ...

The HV-rectifier should be somewhere close to the big cap, the input filter and the ferrite transformer.
The LV-rectifiers can very well be in to220 packages.

[paul18fr]

I start to pick-up some components; I've been looking for information's on the net in order to identify some of them and I found:
http://www.sungho.net/eng/power/settop.php?ptype=view&prdcode=1010270060&catcode=141013

I didn't find the part list, but it is a clearly a complete PSU as identified previously

It's a pitty I've been thinking in classifying them for a futur use ....