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-   -   One Dead Belkin UPS (http://www.aoaforums.com/forum/hardware-hacking/35113-one-dead-belkin-ups.html)

Aedan 19th January, 2006 11:33 PM

One Dead Belkin UPS
 
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Yes, I know that this doesn't normally live here, and might have been better off over in "Crashed", but a) I'm not asking for help (yet), and b) I thought someone else might be interested.

Quick synopsis of what happened:
I had someone around to replace the consumer unit (fuse board), as the existing one did not have enough spaces for some extra wiring that needed to be done. Hence, it was replaced, which required the power to be turned off. Heck, I wasn't worried, as the two UPS devices powering everything should be able to cope.

So, I come home in the evening from work, and discover my Belkin UPS with no lights on. Figuring that it's battery probably died during the power outage, I hit the power button. No joy, so I examined things a bit closer. The battery was charged, so maybe it charged itself back up again after the outage. Figuring that the microcontroller maybe got itself into a tiz, I disconnected the battery and the mains. That should reset the thing! Next step, reconnect the battery, and reconnect the mains.

Time to hit the power button. I was greeted by a loud long beep, followed by silence, and the smell of toasted semiconductor.

Ahh. That might be why it wasn't working. Well, it's out of warrenty, so there's nothing stopping me from taking the thing apart. Step one, remove the battery pack. Shorting that thing would do nasty things to me, so I want to be careful. At the end of the battery pack holder, there are two screws. These are the only signs of anything holding things together.

Aedan 19th January, 2006 11:36 PM

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Well, undoing those screws didn't cause anything to fall apart. After much gentle prying of plastic, I gave up and used more force. It turns out that the front panel comes off first, and that there are a pair of tabs near the top. You have to gently pull the dark plastic away enough (or push the grey plastic towards one side or the other) in order to release the grey front panel.

What do you find behind it? Well, one transformer! This is the reason that the battery pack gets rather warm. The transformer runs pretty warm, and the UPS has no fan in it. That has the side effect of shortening the life of the battery...

Aedan 19th January, 2006 11:39 PM

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Once the front panel is removed, the next step is to try and remove the top panel. In exactly the same way, the top panel is held on, but not with two tabs, but four tabs. One pair at the front and one pair at the back. Gentle force on the tabs is all that is needed. In fact, if you look at the side of the UPS (you can't see it in the pics), you can see where the tabs from the top engage.

I had to turn the UPS on its side to take the picture, so the back of the UPS is facing downwards. Also, you might note that one of the connectors coming from the board on the top (power distribution board) has a distinctly familiar look to it. The mains power from the back of the unit comes directly to this distribution board before being sent to the UPS board itself. The black plastic is just to ensure that 240V doesn't jump across to the logic board!

Aedan 19th January, 2006 11:42 PM

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Next up, the logic board just slides outwards. I also removed the transformer from the plastic casing, as it makes my life easier when testing it. So, the picture below shows all the major parts of the UPS. That's the battery, the transformer and the controller board. The controller board has three RJ45 jacks for protecting networks. There's not a lot there for protection beyond some surge suppressors.

The transformer works both ways, converting mains into 14V for charging the battery, and for converting the 12V from the battery into 240V for the mains.

Aedan 19th January, 2006 11:46 PM

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The issue lies with the UPS Controller itself, but where? The three silver lumps are heatsinks. One for controlling the charge going in to the battery, and two to handle the conversion of 12V into 240V. For the converter, the two heatsinks each have three power transistors attached.

The two blue lumps (on the left) closer are relays to handling switching between the mains and the converter. That way, there's no possibility that the unit is generating 240V at the same time the mains is. You can clearly see the RJ45 and serial connectors - this model doesn't have USB.

If you've got good eyes, then you might be able to see the failure already!

Aedan 19th January, 2006 11:51 PM

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However, I didn't see it, so I had to resort to other techniques, such as trying to see if anything was loose or otherwise damaged. I didn't see what I was looking for, so I took the desperate measure of connecting the UPS controller up to the transformer and the battery. This allowed me to test the controller on a more limited power source with less danger to myself. After all, there *is* 240V present on the UPS controller board when it is working correctly!

Well, the unit powered up for a short period of time, closely followed by a puff of smoke. This gave me the clue I needed to find. There's a set of diodes that appear to act as a full wave rectifier to supply the UPS controller with the power it needs. One of these (second from the left) appears to have died - you can clearly see how it looks rather toasted now! So, I need to replace it when I can.

If you didn't notice in some of the earlier pictures, there appears to be a molex connector. This connector isn't used to carry 12V and 5V - it carries rather more than that! One pair of the pins is used to carry 240V mains from the socket to the UPS board. The other pair of pins is used to carry 240V (mains or generated) to the outputs on the top of the unit!

Daniel ~ 20th January, 2006 12:53 AM

I'd like to see this front page, but have no wish to interfere with any plans for that you might have?

Aedan 20th January, 2006 11:44 AM

Feel free... Hopefully the failure of the diode didn't toast the nearby FET - that appears to control charging the battery from a quick cursory glance.

danrok 20th January, 2006 04:27 PM

How old was it when it failed?

Aedan 20th January, 2006 06:10 PM

It was less than 4 years old.

Kaitain 20th January, 2006 07:28 PM

Quote:

Originally Posted by Áedán
The transformer works both ways, converting mains into 14V for charging the battery, and for converting the 12V from the battery into 240V for the mains.

This is an inverter in one direction and a transformer/rectifier in the other direction, no? My electronics is really shabby - not good, given my chosen career ;)

Gizmo 20th January, 2006 08:19 PM

An inverter changes AC to DC and/or vice-versa, so it is actually an inverter in both directions. However, one direction requires at minimum a rectifier and filter circuit, while the other direction requires at least a switching transistor and wave forming network. In this particular application, the transformer is handy for both operations, because it allows for reducing the input voltage to the filter stage and increasing the output voltage from the switching stage.

It does, however, require a transformer with a bit of a different design from normal. There are tradeoffs you can make in the design of the transformer to increase efficiency when it is always driven from only one side that you cannot make if either winding can serve as the primary or secondary.

Aedan 20th January, 2006 08:20 PM

When running from the mains, it provides power to the UPS controller and to charge the battery. When running from battery, it acts as a inverter. That's one of the reasons for the relays - to switch the configuration.

Gizmo 20th January, 2006 08:28 PM

Quote:

Originally Posted by Áedán
When running from the mains, it provides power to the UPS controller and to charge the battery.

Thus, again, acting as an inverter, but in the opposite direction. Or did I miss something here?

Aedan 20th January, 2006 08:38 PM

No. We posted pretty much at the same time is all that happened!

Kaitain 20th January, 2006 08:58 PM

Ah, thanks for the clarification. I'm still learning about power systems.

Daniel ~ 20th January, 2006 09:11 PM

I tried not to embarrass you, honest I did!

http://www.aoaforums.com/frontpage/index.php

madcatmk3 20th January, 2006 10:05 PM

this is interesting and I understand the basics. But it amases me that you could do this hope your able to fix it.

robbie 20th January, 2006 11:26 PM

So me thinks it got hit with a voltage spike. Is there anything in your house (or on that same circut) that is not working or just behaving oddly?

Aedan 20th January, 2006 11:34 PM

Nope, everything else works fine, including the other UPS. Surge suppression on the top board appears to be intact, and those diodes are not really in the right place to be zapped by a voltage spike as far as I'm concerned.


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