Opening up the Case on an XS 900

[Anonymous user]

Does anyone know the proper procedure to open up the plastic enclosure on an XS 900 model UPS? I've been able to remove the rear panel via the 4 corner screws and disconnect the wiring with no problem. However, separating the case halves is difficult and appears to be "captured" by the front panel assembly. Not wanting to crack or otherwise damage the plastic, what do I do from here?

Thanks!

[voidstar_apc]

You could post the information here for posterity.

[Anonymous user]

Ok. It's probably harder to describe than do, but basically it involves snapping off the front panel which fits around the front edges of the case halves.

IF YOU DON'T FEEL SAFE OR COMFORTABLE WORKING ON ELECTRICAL, ELECTRONIC, AND MECHANCIAL COMPONENTS AND ASSEMBLIES, DO NOT ATTEMPT THIS PROCEDURE!

First, disconnect and the remove the batteries and set them aside along with the unit's battery cover. Next, after removing the rear panel (via 4 screws, one at each corner), the rear panel is gently pulled away. This exposes the rear panel wiring which has 5 leads connecting all of the rear panel sockets etc to the main PC board in the unit. These 5 wires are terminated with crimped push-on type spade receptacles which mate to their male counterparts mounted on the PC board. The wire colors are Black, White, Blue, Brown, and Green-w/Yellow stripe. I made a simple diagram of where each wire connected, although the PC Board also has their corresponding colors silkscreened onto the board as well. These silkscreened legends though may be difficult to see, that's why I made a diagram.

Once the rear panel is free from the unit, set it carefully aside where it can't be damaged or otherwise disturbed. A good clean uncluttered work area is a must. Also, since the unit will be laid on its side, make sure there are no bits of debris on the work surface which could mar the ABS plastic enclosure as it's being worked on. A smooth surface is preferred, but if a towel is used, make sure it doesn't have any bits of solder etc embedded and hidden in the fibers which could scratch the case plastic. I generally don't use a towel for that reason.

This is the process I used as described below and it worked for me. There may be a better way to do this, and/or done with special tools specifically for the purpose. In any event, go slowly and carefully. I take no responsibility for any mishaps, damage, or injuries should anyone else attempt this procedure and fail.

Orient the unit on its side so that the battery compartment is facing toward you and on your left. The exposed rear of the unit will be on your right. Also make sure that nothing obstructs the now-open rear compartment of the unit, as part of the main PCB protrudes from the rear of the case, and could be accidentally damaged if something hits it. A small rectangular opening will be observed in the middle of the bottom edge of the front panel on your left. Gently insert a flat-blade screw driver into this slot so it's blade is inside this opening between opening's front edge and what internally appears as two layers of plastic panels with a small seam in the center. This will be easily seen with the aid of a flashlight. Now gently pry the front panel forward with the aid of the screwdriver so its bottom edge bows out just slightly. Don't overdue it as the front panel could break or be permanently deformed. Keeping the front panel bowed out, notice that the seam along the side of the unit where the front panel meets the case side will expand with the widest expansion nearest the bottom of the unit. With another flat-blade screw driver, gently slip it into the tightest part of this open seam (this point will be closer to the top of the unit than the bottom). Pry with the bottom screwdriver a bit more, and the seam where you have the second screwdriver blade will open wider. Move this screwdriver further up the seam towards the top of the unit to keep it from closing back. DON'T use this screwdriver to twist the opening wider, as it will damage the plastic edges. At this point the seam at the top of the unit should have expanded as well, and with the edges of your fingers pull on the front panel along this seam. It then should snap free from the remainder of the case.

Notice that the now-free front panel is still connected with a flat cable to the unit through a slot in the unit's interior bulkhead. Obviously be carefull not to cut or otherwise damage this cable as you continue work on the main unit of the UPS. You will see along the center of this interior bulkhead, three Phillips-head screws which should be removed. These screws are not overly tight, nor should they be, and they fasten the front portion of the unit's case halves together. Remember that when screwing them back in. Just snug them up, as over-torquing them will strip the plastic threads in the case bosses. Also, in the battery compartment on the right hand side, you will see a plastic boss with another screw (same type and size as the previous three you just removed). Remove this screw as well and save in a safe place with the other three screws. Now, as you pull up on the case half from the back of the unit, you will find that it snaps free and exposes the interior PCB. Just go slowly when pulling it up and it should snap free without any trouble.

I had to open my unit as the fan was making a noise which I suspect was related to bearing wear. The fan was removed and partially disassembled to expose the tiny ball bearing assemblies. These were oiled (and we're talking incredibly microscopic amounts of oil here) and reassembled. So far the fan noise has been eliminated and the fan seems to run a lot smoother and quiter now, even when in its high-speed mode.

Now you will have access to the interior of the unit. Obviously you should be familiar with working on electronic components, especially related to electrical mains power supplies. Also, don't forget there are many static-sensitive components in these power supplies, and proper ESD procedures should be observed to avoid electircal damage to the components such as the MOSFET's and IC's.

Good luck!

[Anonymous user]

Does anyone know the proper procedure to open up the plastic enclosure on an XS 900 model UPS? I've been able to remove the rear panel via the 4 corner screws and disconnect the wiring with no problem. However, separating the case halves is difficult and appears to be "captured" by the front panel assembly. Not wanting to crack or otherwise damage the plastic, what do I do from here?

Thanks!

[jwhite4_apc]

bodycount wrote:
... There is one screw in the battery area that has a ground wire attached to it. You don't remove that screw. Not sure why the ground wire is there as it's screwed into plastic and that's it. ...

It's not a ground wire, I believe it's a thermocouple (temperature sensor). Seeing that it had two lines going to the circuit board tipped me off. Then seeing the same cable right behind the fan I think pretty much confirms it's a temp sensor. I'm thinking this one is to confirm the fan is working (it not working properly, likely the source of a lot of 'overload' failures people report for this model). The one in the battery compartment is probably to make sure the batteries aren't overheating.

[Anonymous user]

Excellent, thanks for the info. I was able to open it all up, remove the two very small roller bearings to clean them and test to see if they are any good. I ended up spraying them with WD40 since that's what I had, and one of the two released some reddish brown gunk onto the paper towel underneath. I can still feel some roughness in that bearing so its definitely on the way out. The fan is still a bit noisy, so I will replace it soon.

I also questioned what is the point of the fan when there is very little for external ventilation in the case. In other words, it seems to me that the fan simply cycles the hot air around inside the case. This seems like a design flaw for sure. So I drilled some holes in the case near the intake side of the fan, and more holes at the rear of the case for exhausting the warm air. It looks bad, but its functional. I might just cut an 80mm hole and cover it with a standard fan grill.

I put it all back together and have had it running for 24 hours or so with a small load, and no faults yet, no overheating. Will put it back into service and see what happens. I ordered a replacement fan from allelectronics.com for $1.75 each plus $7 shipping (got two since they were so cheap). I'll swap that out when they get here.

cheers

[Anonymous user · Accepted solution]

Opening the case is easy. Four screws on the back panel. Front panel pops off and three screws are there. Plus one screw undernear where the battery goes. There is one screw in the battery area that has a ground wire attached to it. You don't remove that screw. Not sure why the ground wire is there as it's screwed into plastic and that's it.

Make sure you unplug the wall plug and the battery and let it sit for at least a day or two. Those compacitors can save up a charge for awhile.. no clue how long though. I waited three days myself to work on mine and it was fine then.