Fix Computer Power Supply

After a week of holiday with AC mains turned off, one of my PC was unable to powered up. I guessed the cause is the PSU. To confirm the rest of the system was OK, I swapped the PSU with a working one proving the PSU is faulty when the PC powered up successfully.

Knowing little about computer PSU, my best bet was to open up and see if there was any burned components that can be replaced. Before opening the PSU, I googled up and concluded that the start-up circuit was probably the culprit, mainly because the symptom was that the PSU is OK if you power cycle the PC without turning off the AC supply, but failed to power on if AC is cut off for a long time.

Next step, I opened up the PSU (keeping in mind that capacitors might still hold charges when handling the PSU). With Tyche at my side, there was one blown capacitor which seemed easy to get replaced.

I replaced the original 1000uF/10V/105°C capacitor with a 1000uF/25V/85°C one since it was the closest thing I could find, knowing that the lower temperature tolerance will cause a much shorter lifetime for the capacitor.

Next thing, power up test. Things you need to test your PSU are a load (I never thought a dead HDD is still useful), a conductor shorting pin 15 & 16 of the ATX power connector, and observe the fan spinning and checking each 12V, 5V, and 3.3V outputs are normal. I used my daily tweezers to do the job.

And the PSU has revived and back to her PC and the capacitor suffers from hot temperature but lived happily ever after. And I forgot to check the capacitor lies in which part of the PSU circuit!

Turn NUSB to USB

We all know the 'U' in USB stands for Universal (though unlikely ET is using it), but some times companies like to make their own universe, even though they know that there can only be one universe in this..universe, they still do so. Some may argue that there are parallel universes but hey, we are talking about USB, S is serial, not parallel!

So, what does NUSB stands for? Read on.

Most electronic devices come with a micro USB cable and a separate charger. Some likes the idea of sharing and using the USB cable for data transfer and charging (save cost?), like my trustworthy HTC charger with a USB receptacle here:

With this you only need to bring one USB cable when travelling. When I got my Sony PSVita, it used the same idea of sharing the cable, but, it had a NUSB receptacle, the Non-Universal Serial Bus. Well in this case I'm talking about the mechanical design (two notches) of the charger the prevent standard USB plug from plugging in, while the pin-out remains the same. Only the supplied Vita cable with special cut-out at both sides is able to plug into the charger.

The urge to bypass the limitation arose when I need to power up my Raspberry Pi, where >1A supply current is recommended for use with a WiFi dongle, and The Vita charger supplied a nice 1.5A current.

The solution? A very simple+short+naked USB extender.

The extender has no problem plugging in to any USB receptacle. And any USB cable can be easily plugged into the Vita charger now.

With this, I only needed to bring one charger and one USB cable when travelling to charge my phone and the Vita. I also made and option for selecting between USB and AC charging using a jumper shorting the D+ and D-. The purpose of picking USB charging is to protect the charger when your device requires more amperes the charger can supply. When USB charging selected, the maximum current draw is limited to 500mA, which are the standard output of older charger.

Speaker Volume Buttons Replacement

I have a pair of Sonic Gear speakers gifted by a dear friend some years ago. After a year serving my ears, the volume buttons started to go wild. The volume will suddenly be increased to maximum levels by itself. For this I had retired them since then, until today I decided to have a look to see whether I can fix the problem. When I checked it, even the Vol- button had failed, both the Vol+ and Vol- button cannot register any pressing action anymore, they failed before reaching 1000 pressing? If I am correct push buttons can last from 100,000 to 1,000,000 times of mechanical life.

Here goes.

The back view of the main (right) speaker:

Opened up to see the PCB & the two dead switches:

Started with removal of the dead switches:

Here were the replacement switches I chose (I did not have much choices). I planned to use the diagonals terminal of these switches to align the switch shaft to the center of the footprints, hence 2 of the terminals have to be cut.

After some usual soldering job, the results were satisfying:

The top view, we can see that the shaft is near the center. The switches will have no problem getting pressed.

Since the replacement switches are higher, the buttons have to be modified next. Luckily it was an easy process to remove one layer of the soft material used to give a premium feel when the buttons are pressed.

And the testing showed the replacement switches worked perfectly:

The truth is, I messed up the terminals of the switches which I was so familiar with, I have to redo the replacement job once more to arrived at the correct mod. You can see that the orientation of the switches in the last picture are different from the previous pictures, and the shafts are exactly on the center now.

Case closed.