Buffalo NAS - Power supply dead

[samstown]

Hi

Buffalo NAS not powering up. Was working for past 10 years, on and off and today, it doesn't show a sign of life.

Before removing drives and trying to rebuild the RAID I would like to see if I can fix power supply and then save all data and buy a second NAS.

I think the AC part is ok. After the big yellow square"filter" nothing... Could be that component, not sure how to measure it. I don't know why I get 320 DC V...

Thanks

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[pepe]

320V DC is the peak-to-peak value of 210V sine. This is where the line filter cap is charged. Be careful, it can keep that charge for a long time after you remove the power from it. And it is a hell of an experience to touch it in that state. Not to mention if you short it to somewhere, where you shouldn't

the yellow 'filter' is a transformer, it should get a switched voltage, swithed by the MOSFET (big black brick mounted on the right side of the heatsink).
UC3843 is the controller IC.
there can be plenty of reasons why it is dead, and you won't be able to determine it using a multimeter alone.
So I would rather go with some other PSU to power up the NAS. check the output voltage and current ratings, i guess it will be 5V and 12V, so you can feed it from a PC supply (probably).

pepe

[fzabkar]

That "filter" is a transformer. I think you probably should stop before your lack of understanding kills you.

The 320VDC comes from the large bulk capacitor (C101). When working on the PCB, you should first discharge it with a 100W incandescent lamp load.

The typical failures with these circuits are the capacitor and startup resistor on pin #7 of the IC.

The startup resistor often goes open circuit. The symptom is that the bulk capacitor retains the rectified mains voltage (340VDC or 170VDC) even after the mains power is switched off (BE CAREFUL), and the IC never gets a Vcc to kickstart it. I suspect that R101 and R102 may be the corresponding startup resistors in your circuit.

A leaky capacitor prevents the IC from getting an auxiliary supply from the transformer. The symptom is that the IC wants to start (by pulsing the MOSFET), but cannot keep going because the Vcc fades away. This happens many times in succession, sometimes resulting in an audible "hiccup". This capacitor is the 100uF cap in the application circuit, just after the 1N4935 diode. C100 in your circuit is probably the same cap.

Datasheet for UC3843B PWM controller:
https://www.st.com/resource/en/datasheet/uc3842b.pdf

This datasheet has an application circuit which probably matches your own:
https://www.onsemi.com/pub/Collateral/UC3842B-D.PDF

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[jono-ats]

By a replacement on eBay?

[ShaneWard]

I think your main NAS unit is okay, you just have to get the power supply fixed or replaced. Take it to a electrical repair shop and they should get the power supply working again. Otherwise, use the silver label on the capacitor to order a new one form E-bay, but I am not sure if there are any on there. Its more likely what fzabkar said, a shop can fix it for you if you don't know what you're doing.

[fzabkar]

If the OP is measuring 320VDC after switching off the power, then I would examine those two startup resistors. They should cost less than 1 Euro.

BTW ...

230VAC x sqrt(2) = 325VDC

That's what you get when you rectify the mains voltage.

[jono-ats]

If you know what you're doing, great.

If you don't, stop what you are doing and spend $17.50.

Problem solved.

https://www.ebay.com/itm/POWER-SUPPLY-A ... XQCgpRv4GI

[pepe]

Of course Franc, you can do it and I can do it too, but it is not wise to recommend somebody with little knowledge in electronics to mess with PSU, line voltage, etc. Can you also repair dead people? Remotely?
BTW, when dealing with PSUs i always use isolation transformer, which could give me a second chance if i get into a more intimate relation with the target than desirable.
I think you should just stop giving tips on this one, coz somewhat more valuable things are put to risk than 'just' hdds and data.
Maybe if you were standing behind him, but from Australia?
consider your limits.

https://www.ebay.pl/itm/POWER-SUPPLY-UN ... 2689431274
it is clear this supply creates 5 and 12V for the NAS, he could just use a PC psu, connect GND, 5V and 12V to the NAS and get recover the data.
And no monkeys, dolphins or human beings would be killed in the meantime.

pepe

[fzabkar]

Of course Franc, you can do it and I can do it too, but it is not wise to recommend somebody with little knowledge in electronics to mess with PSU, line voltage, etc.

I think you probably should stop before your lack of understanding kills you.

His life, his choice.

Others would benefit from this post, so I have provided as much information as possible, including warnings and safety tips.

I also have isolation transformers, but I confess that I don't use them, unless I need to hook up a mains powered scope.

[pepe]

His life, his choice.

egoist.

[samstown]

Hi,

I got this sorted. I connected external power supply 5V and 12V and it's working.

I will have a look at the power supply with a friend of mine. Thank you for all your help and recommendation.

Thanks
Sam

[pepe]

good.
... and still alive

i hope your friend knows his stuff.

pepe

[fzabkar]

eevblog.com is a better forum for these types of jobs. Many experienced component level techs hang out there.

[pepe]

sure, and it is no problem with low voltage stuff, but repairing a PSU, which involves line voltage and stuff like that is not for newbies whatever forum they ask for help on. too much to risk for 20 eurs.
I am also for repairing all that's possible, but there's plenty of stuff behind me, lots of SMPSs, arc lamp ballasts, etc, so that's something a newbie doesn't have in his/her pocket, and the risk is not negligible.

Btw, i am looking for firmware for a whirlpool ADG7556/1 dishwasher, if you have any idea where it may be possible to find it...

pepe

[fzabkar]

sure, and it is no problem with low voltage stuff, but repairing a PSU, which involves line voltage and stuff like that is not for newbies whatever forum they ask for help on. too much to risk for 20 eurs.
I am also for repairing all that's possible, but there's plenty of stuff behind me, lots of SMPSs, arc lamp ballasts, etc, so that's something a newbie doesn't have in his/her pocket, and the risk is not negligible.

Btw, i am looking for firmware for a whirlpool ADG7556/1 dishwasher, if you have any idea where it may be possible to find it...

pepe

Eevblog is very tolerant of novices who are repairing their own gear. The OP's job is a very trivial one which can be done safely with a multimeter and a 100W lamp (to discharge the bulk capacitor). I have probably repaired 1000 PSUs, and the OP's topology is a very common one, with common faults. There is often no need to power up the PSU when testing it. I can count on the fingers of one hand the number of times I've had to use a scope for a PSU job.

As for the firmware, try eevblog.com or badcaps.net. I doubt you'll find it, though. I'm guessing there is no discrete flash memory IC? That's usually the case with domestic appliances.

[pepe]

yes, that thing has a HCS08 based microcontroller with internal flash. It kicked the bucket because the thyristor array blew up. I already repaired this control board last year, the switching supply said goodbye that time, it was pretty easy back then but now it got a final strike :s

Since these controller units are pretty pricy (100-180eurs, but one can buy unprogrammed boxes for 15) I would think there's a point for fanatic people like us to repair these, so perhaps some people keep an archive of such fw...
It is quite against environment friendliness that all the parts for these appliences cost 10 times their new price, so manufacturers push us to buy new and bin the old one, which i don't really like ...

[ghimpe--]

Also try elektrotanya.com

[fzabkar]

... or https://www.eserviceinfo.com/