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.
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.
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.
Guess how I discovered that?
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.
Stupid cheap screw. How much torque do you need on this thing? Sheesh.
There are four screws holding the board in place.
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 AC line connector (white) needs to be unplugged from the board to get the whole assembly free to work on.
Now we can get at those caps and replace them.
Fortunately he's healed and back doing beautiful work.
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!
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.
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.
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?
Reconnect that AC plug to the power supply board, and connect the AC cable to the IEC connector.
'Studio' in this case is a small corner of the bedroom.
Now let's make some noise.