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Acer AL1716 LCD capacitor replacement
These pages describe how to replace bulging capacitors in an Acer AL1716 17" LCD computer screen.
Replacing the faulty capacitors in an Acer AL1716 can be done in less than an hour.
Symptoms
I recently picked up two Acer AL1716 17" LCD computer screens that were about to be thrown out.
However, I soon found out why they were being discarded, as they were not working at all.
After applying power, the power LED flashes green, and nothing was displayed on the screen.
Both screens were exhibiting identical symptoms.
Diagnosis
Some googling quickly turned up stories of other people experiencing the same symptoms with this particular model
LCD screen, but finding a solution took a little more digging.
I found this discussion thread,
where someone confirmed that the issue is caused by failing capacitors in the power circuitry,
and they provided a brief overview of the steps required to replace the capacitors.
Capacitor Issues
Failing electrolytic capacitors in electronics are not uncommon, and is caused by companies using
incorrect electrolyte formula in the capacitors in 1999 and 2000. Production of hydrogen gas in the
capacitors causes bulging or deformation of the capacitors, and in some cases, can cause the capacitors
to explode.
The capacitor plague (as it is sometimes called)
affects many electronics, including computer motherboards, video cards, LCDs and other devices.
In many cases, electronic devices affected by the capacitor plague can be repaired by simply replacing the
faulty capacitors.
With the Acer AL1716 LCD screens, if you're reasonably proficient with tools and a soldering iron, this is a
fairly easy exercise.
Sourcing Replacement Capacitors
You'll need the following replacement electrolytic capacitors:
- 1 x 470uF 10V electrolytic capacitor (Jaycar cat RE6302)
- 3 x 470uF 25V electrolytic capacitor (Jaycar cat RE6326)
- 2 x 1000uF 10V electrolytic capacitor (Jaycar cat RE6304)
Note that the replacement capacitors need to be rated at 105 degrees C.
figure 1: replacement capacitors
Total cost of these 6 capacitors was just AUD$4.64 from my local Jaycar Electronics store.
Caution
Disconnect the power cable and data cable from the LCD screen before proceeding with the disassembly of the screen.
Capacitors in power supplies can hold high voltages for quite some time after they are disconnected from the mains.
Be careful not to come in contact with the terminals of the capacitor on the high voltage section of the PCB.
Use a short length of insulated wire to short out the terminals of the large capacitor to dissipate
any charge that the capacitor may be holding.
Disassembly
Place the screen facedown on a table or workbench. To ensure the front bezel isn't scratched,
place a cloth underneath the screen.
Remove the plastic cover at the top of the stand by gently squeezing the top and bottom of each side
(as shown in figure 2 below), and it should separate from the back of the screen.
figure 2: squeeze and lift to remove cover
Remove the four screws holding the stand to the rear of the screen (circled in figure 3 below),
and then remove the two screws holding the rear cover of the screen (the bottom two screws circled in figure 3 below).
figure 3: the top four screws hold the stand, the bottom two screws secure the rear cover
The rear cover of the screen can be removed by carefully levering it off with a screwdriver.
After working around the entire screen levering it off, the rear cover can be removed.
figure 4: lever the rear of the case
Six cables connect the PCBs to the screen itself (arrowed in figure 5 below), and four screws hold the rear
metal assembly to the main frame (circled in figure 5 below).
The next few photos provide details on removing the PCBs from the main frame.
figure 5: six cables need to be disconnected (arrowed),
and four screws hold the metal bracket to the screen (circled)
The multi-coloured cable connecting to the front panel needs to be removed by levering it out with a screwdriver.
Lift one side of each piece of yellow tape holding the cable to the main frame, and remove the cable from underneath the tape.
figure 6: remove the cable to the front panel
Lift the two pieces of black tape on the side, and unplug the four cables that connect the screen's backlight to the PCBs.
To ensure you re-connect these cables correctly, make a note of the order of the cables.
figure 7: screws and backlight cables hidden underneath tape
The data cable at the top of the screen needs to be removed. First lift the black tape and yellow tape to expose the connector,
and then lever the connector out of the socket when squeezing the sides of the connector inward.
figure 8: remove the LCD data cable at the top of the screen
After disconnecting the cables, the four screws holding the rear metal assembly to the main frame can be removed,
and the metal assembly containing the PCBs can be removed.
Use pliers to remove the two lugs holding the VGA connector to the metal assembly.
figure 9: remove the lugs holding the VGA connector in place
Remove the black insulating plastic (not shown) from the rear of the PCBs.
Remove the seven screws (circled in figure 10 below) that attach the PCBs to the metal assembly.
figure 10: remove the 7 screws holding the two PCBs to the metal bracket
Remove the two PCBs from the metal assembly. The two PCBs are attached via a 6-pin connector (circled in figure 11 below),
and can easily be separated.
figure 11: the two PCBs are attached via a 6-pin connector, and can easily be separated
Examine the six electrolytic capacitors in the low voltage section of the PCB (indicated in figure 12 below), and check if the tops are bulging.
figure 12: suspect electrolytic capacitors
All six capacitors on both the screens I repaired had bulging tops, and were clearly
suffering from capacitor plague.
The Culprits
Here's a couple of photos (figure 13 and 14) showing the electrolytic capacitors with bulging tops.
figure 13: the cause of the issue - bulging electrolytic capacitors
figure 14: side view showing the bulging capacitors
Capacitor Replacement
Desolder each of the capacitors, remove it from the PCB, insert a new capacitor, and solder it into position.
Electrolytic capacitors are polarised, and need to be re-installed in the correct orientation
on the PCB.
Figure 15 below shows the PCB with two of the capacitors removed. The shaded portion of the capacitor
outline indicates the negative terminal of each capacitor.
figure 15: two capacitors removed - the shaded area indicates negative terminal for the capacitors
Replace all six of the electrolytic capacitors on the PSU PCB, ensuring you replace each capacitor with an equivalently rated
capacitor.
figure 16: the PSU PCB with replacement capacitors installed
Reassembly
Reassembly is the reverse of the disassembly described above.
Once the LCD screen is re-assembled, apply power, and the power LED should no longer flash green,
but the screen should function correctly.
last updated 13 Dec 2009
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