WD My book reverse polarity connection. Need help with burnt smd

[goodpsusearch]

Title says it all.

Customer had lost/broken the original psu and bought a general purpose power supply with variable voltage selector and the ability to remove dc jack and fit it backwards. He sent -12V at the controller and some smd caught fire, as you can see in the pictures attached.

I am lucky to have the same controller here, so I upload some photos with both the good one and the "bad" for comparison. The pcb layout is different, but the burnt components markings are the same.

What is L20 and how can I replace it with something compatible? Should I just jumper it?

[kaboom]

Re: WD My book reverse polarity connection. Need help with burnt smd

It doesn't look like there ever was an L1 on the board with the blown SMD cap.

From what it sounds like, one of these was used:
http://www.mysmartbuy.com/p-322-Lloy...s-Adaptor.html

Since they're just an unregulated supply, the supposedly "12V" can be 18-20V under light, or no, load. What's worse, I don't see any polarity diodes, so some MOSFET body diodes, like in the unit's buck converter, would've taken that reverse current.

The original adapter was an SMPS, which would presumably hold it's output at 12V at all times.

Test all the power semis for shorts, but unless you got lucky, you'll be dealing with tiny SMDs.

Edit- that blown part may not be an SMD cap, I was misreading the silkscreen. Whatever that is, try removing it, testing at the DC jack for shorts, and try powering it from a DC supply with maybe a 10-ohm resistor in series.

[goodpsusearch]

Re: WD My book reverse polarity connection. Need help with burnt smd

L20 on the burnt pcb is smaller than L20 on the other version. In fact there are 2 places for L20 on the burnt controller, one for "large" L20 and that was indeed empty and the other is smaller and was populated with a "small" L20 that is severely damaged. The 2 smd caps C14 and C29 might be ok.

[goontron]

Re: WD My book reverse polarity connection. Need help with burnt smd

thats an overvoltage man. ceramic caps are non polar, and what appears to be C29 is blown to bits. i vote on non-switchmode PSU usage. common lowest denominator voltage wise is 16v, so it probably seen at least 19v (ceramics usually do fine at +2v)

[goodpsusearch]

Re: WD My book reverse polarity connection. Need help with burnt smd

I think the markings go like this:

[goontron]

Re: WD My book reverse polarity connection. Need help with burnt smd

I think the markings go like this:

ok, i see. does the via that it is connected to go through all the way or does it stop at the center ground plane?(assuming ground plane from Hitachi board i have on hand)

[stj]

Re: WD My book reverse polarity connection. Need help with burnt smd

is it 12v anyway? a lot of externals i see are 5v wih internal boost circuits

and did you test the drive?
because if it is supposed to be 12v the 12v may go directly to the drive aswell as the 5v regulator circuit.

[stj]

Re: WD My book reverse polarity connection. Need help with burnt smd

one other thing, if the inductor is destroyed then something downstream is shorted - maybe a ceramic cap if your lucky.

[goodpsusearch]

Re: WD My book reverse polarity connection. Need help with burnt smd

It is 12V. The drive is completely healthy. The burnt component is "smd ferrite bead" or "smd inductor" according to pages like these:
http://katalog.we-online.de/en/pbs/WE-MI#vs_t2:1
http://www.token.com.tw/rf-inductors/chip-beads-ma.htm

[momaka]

Re: WD My book reverse polarity connection. Need help with burnt smd

Just replace the burned ferrite bead with a piece of wire. - I know, ghetto and not quite right, but in a pinch, it works just to see if everything else is okay.

Also, most HDDs have a reverse polarity diode . So if the HDD uses 12V, and its 12V line was directly connected to that on the input connector, then that's what likely caused that ferrite bead to burn out. Otherwise, your HDD would have likely stopper working too.

That means, you may be just lucky and the controller board may be working after all. But if it isn't, then the MOSFET(s) in the 12V->5V buck converter may have gone bad (Q2 on the bad board).

Just make sure to clean that burned area very well before powering it again.

[goodpsusearch]

Re: WD My book reverse polarity connection. Need help with burnt smd

Just replace the burned ferrite bead with a piece of wire. - I know, ghetto and not quite right, but in a pinch, it works just to see if everything else is okay.

Also, most HDDs have a reverse polarity diode . So if the HDD uses 12V, and its 12V line was directly connected to that on the input connector, then that's what likely caused that ferrite bead to burn out. Otherwise, your HDD would have likely stopper working too.

That means, you may be just lucky and the controller board may be working after all. But if it isn't, then the MOSFET(s) in the 12V->5V buck converter may have gone bad (Q2 on the bad board).

Just make sure to clean that burned area very well before powering it again.

It worked

But now what? Shouldn't I replace the wire with ferrite bead? Can I just pick one from a dead motherboard pcb?

[momaka]

Re: WD My book reverse polarity connection. Need help with burnt smd

Good to hear it works .

Well, it's better to have it since it reduces some electrical noise from the PSU/adapter going to the board and the HDD. But if you leave the jumper, I doubt this will affect the life of the hard drive. Just make sure the PSU/adapter has good caps.

And if you really want to add it from a dead board, then you can. The inductance and current ratings might be different, though, with the current rating being more important. Just check that the "new" replacement ferrite bead doesn't overheat in normal HDD operation and everything should be okay.

[goodpsusearch]

Re: WD My book reverse polarity connection. Need help with burnt smd

Here are some photos of the variable voltage output switching power supply.

The input filter is just an NTC thermistor and a common mode choke.

There is no MOV for surge suppressing

The primary caps are 2x Rubycon YXA 400V 10uF in parallel. So, the total C is 20uF. For a 30W psu I find it low.

13007B is the switching transistor.

MBR20100 is the output rectifier, rated at 20A max output.

Output filter is 1x "SNE" 16V 1000uF, a coil and 1x SNE 25V 470uF. I am considering to recap those. I don't know if it is worth the hassle.

Would you keep it or it ?

[momaka]

Re: WD My book reverse polarity connection. Need help with burnt smd

The built quality (soldeing, part placement, etc.) looks crap, and those Rubycon caps on the primary seem "dodgy". But other than that it doesn't seem too bad. I wouldn't use it to power an HDD/HDD enclosure with it, though. Probably okay for a router or modem since those have their own internal down-converters inside. It's a classic 2-transistor flyback (like the 5VSB in older PC PSUs). If designed well, it can perform decently.

Before you even attempt to recap it, I say load it up and see how it performs. If you can pull 10W out of it on any of the settings (and preferably close to 15W @ 12V) without too much output voltage sag, then it's worth saving.

I would also definitely recommend adding a fuse on the primary.

[lti]

Re: WD My book reverse polarity connection. Need help with burnt smd

Those aren't Rubycon caps. I've seen that SL36(M) marking on Rukycon and Retycon caps (both Rubycon ripoff brands).

[stj]

Re: WD My book reverse polarity connection. Need help with burnt smd

wa haha - 2 cap brands with the same K vent.

[dragos2009]

Re: WD My book reverse polarity connection. Need help with burnt smd

check the leg of the inductor i have circled in the photo it looks like some corrosion affected it

[goodpsusearch]

Re: WD My book reverse polarity connection. Need help with burnt smd

I replaced the SNE 1000uF 16V cap --> Nichicon HD 1000uF 16V and the other SNE 470uF 25V capacitor --> Teapo SH 1000uF 16V

About the output coil, I checked the solder side, fortunately there is no corrosion there.

[goodpsusearch]

Re: WD My book reverse polarity connection. Need help with burnt smd

Good to hear it works .

Well, it's better to have it since it reduces some electrical noise from the PSU/adapter going to the board and the HDD. But if you leave the jumper, I doubt this will affect the life of the hard drive. Just make sure the PSU/adapter has good caps.

And if you really want to add it from a dead board, then you can. The inductance and current ratings might be different, though, with the current rating being more important. Just check that the "new" replacement ferrite bead doesn't overheat in normal HDD operation and everything should be okay.

I followed your advice and the controller is now working like new!

I took the ferrite bead from a dead Intel P4 SDRAM motherboard.

It doesn't overheat, I wish it helps with noise coming from cheap AC Adapters.

[momaka]

Re: WD My book reverse polarity connection. Need help with burnt smd

Nice! Good to heat it is working again.
That ferrite bead is mostly for protecting from large power spikes. But it probably helps a little bit with the ripple too.