Crawls Backward (When Alarmed)

IconProjects, musings about guitar builds, guitar repairs, vintage tube amplifiers, old radios, travel, home renovation, and other stuff.

Replacing Electrolytic Capacitors in Dell Optiplex 780 Power Supply

The other day, I tried to turn on the Dell Optiplex 780 computer which is my studio machine. It did nothing. So after some investigation of this issue on the interwebs, it appeared that the power supply might be not working.

Seems this is not uncommon on these machines, and the fault is usually failed electrolytic capacitors! Can you believe it? I have years of experience in replacing capacitors in radios and amps, so I was encouraged that the problem was something I could fix.

I took it apart to test it and recap it if needed.

Here's the patient. I bought this machine used, and upgraded it to 32GB of RAM and put an Asus Xonar sound card in it.

We take the cover off to get to the innards.

All of the various bits come out easily. There's actually a diagram on the chassis that illustrates how the pieces come out.

This is the Western Digital Caviar Blue hard drive. Squeeze the two blue tabs and it comes out. Then you can remove the ribbon cable that connects to it.

The drive needs to come out so you can get to the main connector from the power supply to the motherboard.

So, Caviar Blue? I had the greatest caviar ever in Stockholm about 2003 when I was on an automotive press junket covering the then-new SAAB 9-3 Sports Sedan. But it was not blue.

Same general approach for the DVD drive. Push a tab, remove the drive and its connectors. We need to remove this drive to get to another connector underneath.

Under the DVD drive is another power connector from the power supply to the motherboard. There's a clip on the side that releases to remove the connector.

And this is the main connector under the hard drive I mentioned earlier. Like the white connector above, it has a clip that needs to be released in order to remove it.

Three screws on the outside of the chassis hold the power supply in place.

You can see there is a power supply test button on the right to the IEC AC connector. If you press it with all of the peripherals disconnected (the drives), the green light alongside it will turn green, and the fan will spin, meaning the power supply is ok. Mine failed this test.

The power supply can now be removed from the computer.

The aluminum box holding the power supply is held together with a bunch of Phillips head screws. Most of them will take a bit of torque to turn. They are also cheap and the heads will be damaged easily.

Guess how I discovered that?

If I cut this anti-tampering label, my guarantee will void.


The label cleverly covers one of the screws we need to remove.

Long story short.

One of the stupid screws was so tight and frozen in place that I couldn't remove it, and my trusty Wima screwdriver began to strip the head! Even soaking with PB Blaster didn't help.

So I wound up drilling the screw out.

And then removed it with a screw extractor. I have a couple of sets of extractors (aka easy-outs) around and they come in handy.

Stupid cheap screw. How much torque do you need on this thing? Sheesh.

The various cables are secured to the case with a wire tie, which we need to snip off.

The top of the case comes off, exposing the power supply board.

There are four screws holding the board in place.

Sure enough, there are a number of electrolytic capacitors with bulging tops, a clear sign they have failed.

I generally don't see this in old radios or other gear - in those applications, the caps have just become electronically 'leaky' over time. Those old caps almost always look ok, but they are bad. You can't generally tell they are bad by just looking at them.

This is one of the rarer instances where the caps are visibly bad.

The yellow arrow points to the hole in the PCB for one of the mounting screws (screw removed). I took this shot to show that the test switch (hanging loose above the hole) needs to be removed to access this specific screw.

With the screws removed, you can lift the power supply assembly out of the chassis.

The AC line connector (white) needs to be unplugged from the board to get the whole assembly free to work on.

Here's the power supply removed from the chassis/cabinet/case.

Now we can get at those caps and replace them.

I have a saying: it's not a project unless there's an injury. Not as extreme as Sven's though.

Fortunately he's healed and back doing beautiful work.

Removing the caps on a computer is no different than any other piece of equipment. I prefer solder wick over solder suckers. The cheap suckers (ha ha) are useless. Wick gives you a much cleaner hole or connection to work with.

One thing I found with this board is that the solder Dell uses doesn't like to come off easily. I heated it as usual, but no dice. I suppose it's lead-free solder. I'm all for it in theory, but my few experiences with it haven't been that great. Mainly, as on this board, it's the very Dickens to desolder.

But I have had success working with it: I melted a bit of new solder onto each joint, and then the joints came clean easily. Just something to be aware of.

Keep your iron's tip super clean too - the pic above is NOT a good example. I'm really good about keeping it shiny, but that's not evident there!

One thing I really liked about this pcb is the way the polarity for the caps is marked - the shaded black area is negative. Makes it easy to identify.

On this specific spot, the two caps in the back were buried under white silicone. So much silicone, in fact, that I didn't even see them when I first had the power supply out and was making a list of caps to buy from Mouser. Fortunately I had those two values on hand.

I try to use the best quality caps I can in stuff I work on, which means Nichicon, Panasonic, or ELNA.

This is the biggest cap on the board - rated at 450 volts. You can see the original 'Elite' brand cap versus the new Nichicon I replaced it with. Ever heard of Elite? Me neither.

Unfortunately, a lot of modern gear uses cheap components such as this cap. This is why there is a high failure rate- this computer was built in 2009, yet the power supply caps have failed. I generally see a 20 to 25 year life in gear I work on - which had quality components to begin with.

Places such as Mouser only sell good stuff. Don't be tempted to try and 'save' money by using no-name stuff in gear you repair or build. Generally, the price difference is only a few cents and the peace of mind and performance difference far outweighs the perceived cost savings.

Here's the power supply, freshly rebuilt with new electrolytics. Got rid of a bunch of that awful silicone too.

I believe there were a dozen caps I replaced.

Why would I do this versus just buying a replacement supply, you ask?

First, cost. I put less than $10 worth of parts into this, as opposed to $55 for a new supply. I could recap 5 of these for the cost of just 1 new one.

Second, a new supply would use those poor quality parts the original did!

Third, other than the capacitors, everything else on the board works fine. Why trash it?

Moment of truth.

Reconnect that AC plug to the power supply board, and connect the AC cable to the IEC connector.

Press the test button and the fan spins! Whoo hoo! We have a good power supply!

Now we just reassemble the whole power supply and put it back into the PC.

Here's the power supply back in, along with all of the drives reconnected.

The real test, of course is to connect it back up in the studio and boot it up.

'Studio' in this case is a small corner of the bedroom.

It works!

Now let's make some noise.


UDI007 Voyager Radio Controlled Boat Upgrades

I was Out West last week. The house where I was staying has a pool, so I procured a USA Toyz UDI007 'Voyager' radio controlled boat to play with. I had also read about some mods/improvements for it, and I did those.

Set up an informal work space right beside the pool. Sort of like The Dungeon, but with substantially better views, ventilation, and natural light. Fortunately I also had a nice tool box full of good tools at my disposal, so this went well.

The boat is a good compromise between a really cheap toy and a serious R/C model.

We'll be adding some additional waterproofing, relubing the drive/propshaft, and protecting the electrical connectors.

With the hatch removed, we can access the innards.

The motor gets hot, so the manufacturer wisely fitted it with a simple water cooling coil. There is a water intake hose (blue arrow) attached to a small scoop under the hull.

That hose runs to the coil (silver coil around motor on the right), and then another hose (green arrow) exits the port side of the hull. (Me talk boat terms!).

We're going to put some silicone around those connections to make sure water can't get in. You can see the white silicone applied at the factory around a couple connections already.

I'm going to remove the driveshaft and relube it with marine grease. Removing the shaft will also give me better access to the intake of the cooling hose.

There's a mount that holds the front of the shaft in place. We remove those 2 screws.

Then remove the 2 screws holding the motor mount down.

Now we can lift the ends of the motor and the propshaft and separate the drive on the motor from the shaft.

Remove the nut holding the propeller onto the shaft. I didn't have a small enough wrench on hand to fit the nut, so I carefully used pliers to remove it.

Nice vintage Craftsman pliers.

The prop is threaded, so you'll need to unscrew it from the shaft also.

No expense was spared here to make sure the prop doesn't come off and wind up in the bottom of a lake.

I have a lifetime supply of marine grease. I'll use a tiny bit on the drive shaft on this boat.

Gently tilt the brass propshaft upward and you'll be able to slide the inside drive out.

The prop end of the shaft is held in mainly with silicone, so I didn't want to force the whole thing out - just raise it enough to get the drive out.

I cleaned the old lube off and stuck the shaft into the tube of grease to coat it.

Any excess will be forced out the open end of the shaft when the drive is put back in. It doesn't take a lot of grease to lubricate the drive.

With the propshaft raised up, I put more silicone around the point where the shaft enters the boat.

I also put silicone around the cooling hose where it enters also.

And we put silicone around the exit for the hose as well.

The idea is to close up the points where water might enter. I don't think it will be totally waterproof, but the less water that can get in, the better - and the less chance the motor, receiver, servo, or connectors could get damaged.

There's a rubber cone that the servo pushrod for the rudder passes through. The stern rides low in the water, so this is a place where water can enter.

The cone slides right out from the hole it's mounted in.

I packed it with marine grease - to lubricate the rod, but mainly to keep water out.

Then I put the cone back on and put silicone around it to seal the outside.

Finally, we'll put some dielectric grease on all of the electrical connectors.

There are 4 points in the wiring where there are connectors. The all come apart easily.

I used a toothpick to put the grease on all the connectors. Thrilling, huh?

Here's everything reassembled. It only took about 20 minutes to do this. Now we're ready for a test voyage.

The gasket around the hatch doesn't fit that tightly, so I'm using "hatch tape" (aka PVC electrical tape) around its perimeter to get a better seal.

I also wrapped the electrical connectors with the tape for extra insurance against water.

Whoo hoo!

Lots of fun.

The boat's pretty fast - I can only pilot it on full throttle before I run out of pool. I'd like to try it on a lake.

More of a close up shot.

I fiddled with the adjustments on the servo arms and got it to turn tighter than it did originally. Now I can make complete circles easily in the pool.

I managed to capsize it a couple of times, and only a small amount of water got into the boat - which I think is pretty good.