Repair.IT – Power supply for a NetGear ReadyNAS Pro RNDP2210

As you can imagine, I quite often get things given to me on the off chance that it may work out to be repairable or maybe used for parts. These things are usually checked when it arrived to be catalogued as either working, non-working, repairable or non-repairable, etc. This NetGear ReadyNAS Pro 2 bay NAS was in the same boat. It was given to me by a friend who said they have a couple of old NAS’s – am I interested in them? I said yes at the time and didn’t think much about it until one day I happened to arrange to meet my friend as we were going to the same place and I was giving him a lift. He gave me the NAS’s at that time.

When I got home, I inspected them – to see what I have received. One had a power supply, the other did not. I decided to power up the NAS with the power supply and it didn’t power up. The light indicator on the power supply was not lighting up, so essentially bad power supply or is it? As luck would have it, I have another of these identical NAS’s – also from my friend but years earlier. I took the power supply from that one, and tried the NAS and it powered up – thereby confirming that the power supply was at fault.

Then it was left for a while and one day, I had a look to see if I can get the power supply open. It is one of those that are in two halves, and seem to be glued or ultrasonically welded. I might have mentioned before that a rubber mallet can be useful in breaking the glued seals and since it wasn’t working, I couldn’t really damage it any more by pounding on it with a rubber headed mallet. In due course, the seals gave way and I was able to prise the case apart. As soon as it was open, I could see the problem – blown electrolytic capacitors on the output.

Usually, they will just have a shiny top, not bulged and blackened like these ones were. I was able to read the values of the electrolytics, which were 1500uF 16V and 1000uF 16V. These were also the high temperature 105 degree versions which are common for power supplies in enclosed tight fitting containers. I checked on ebay, and found a suitable supplier and ordered some. I didn’t bother to match up the original specifications since the replacements should be much better than the original faulty ones. If this was a precision repair, then it would make sense to do this.

This was placed aside and only this morning, I was wondering, where were the capacitors I ordered over a month ago. I checked the delivery status, and it just showed in transit. Then this afternoon, my wife brought in the mail, and in that was a brown padded envelope that looked like it might have a couple of packets of capacitors stuffed into it. It was, and I checked the values and they were what I ordered – a bonus sometimes. As I was still busy doing some PowerShell scripting, I had to leave that until the evening, after dinner had been squared away – then I had some time.

Out came a desoldering station – it was having a bit of a hard time melting the solder since the solder used in the power supply was lead-free. Also due to the reflow soldering method, the joints don’t have an excess of solder and lead-free solder has a higher melting point. To help it along, I tinned each capacitor joint with leaded solder – and then was able to desolder each solder joint and then with a slight wiggle, both capacitors came off without any further trouble. It was an easy exercise to match up the polarity of the capacitors – for the replacements to fit back, with the correct orientation. The white stripe on the capacitors indicates the negative pin (not always white – my replacements had a yellow stripe since the printing was in yellow, but you know what I mean).

Here they are shown soldered in place with the old faulty ones on the side. Next step to put the case back on, and close it up – without sealing it up permanently. Power on, and I could see the led indicator lit up, so it should be ok to attach the NAS.

You can see the NAS powered up, and I am holding the power supply at an angle so I could capture the lit indicator. So there it is – I ordered $7.67 worth of capacitors, and used approximately $0.77 of the order, so I have a lot of spares in case I need them in the future. To buy them individually might have cost me about $4 anyway, so this way, I get extras. With this repair, I will leave it running as it is for a day or so, then seal up the power supply. Have a good evening!

I didn’t mention, but the NAS did have two hard drives still installed inside of it – I wonder what’s on them…

Recap.IT – Aldi Vivid 32″ LCD TV

One of these Aldi TV’s came in – a Vivid 32″ LCD TV with a problem where the screen display goes out from time to time. I had seen it happen a couple of times, and could see that it was the backlight that was the problem. However, the backlight circuitry appears to be working fine most of the time, so the fault could be due to the power supply.

The power supply is a Megmeet MP-116A – a search of google shows that a lot of people have had problems with this power supply. Also searching for Vivid 32″ shows some similar faults but no real fix.

I checked most of the electrolytic capacitors, they all appear to be within tolerance as far as ESR is concerned. ESR or Equivalent Series Resistance is a measure of how well a capacitor is working, in addition to its capacitance. Power supplies tend to get quite hot, and when capacitors get hot, they can start to dry out – and noticeably it’s ESR tends to increase, until eventually it is unable to filter out any ripple currents effectively.

I also used an oscilloscope and looked at the 12V output of the power supply – it was showing some 200mV of ripple, not a lot but could be causing a problem if the ripple increases during higher loading.  The large main capacitor ESR was not high, at 0.66 ohms, but usually this is one that would go first.

In any case, it is usually best to “recap.it“, i.e. replace all of the electrolytic capacitors – so this is what I did. I got the parts yesterday and replaced them today. After removing the parts, I also checked the actual capacitance and found a couple that appeared to be slightly low, but most were within tolerance. I will test it further during the weekend and see if the backlight fails again – if it doesn’t, then it could be that replacing the capacitors in the power supply did the trick.

[NOTE]  The replacement 68uF 450V main capacitor as a comparison had an ESR of 0.2 ohms – this means that its power dissipation for ripple currents will be considerably less than the original capacitor, and hopefully run cooler.