Recently, a friend of mine told me that his blackberry 8900 curve won't boot up anymore and when plugged in the wall socket, a battery icon with a red cross across would show. Researching online, it was evident that a lot of people were also having the same issue but there was no adequate solution. "Solutions" proposed ranged from leaving the phone plugged in the wall socket for 24 to 48 hours (some even went to a week if I recall) to banging the phone (out of desperation maybe?). On the other hand, I did read a few comments whereby people were charged somewhere around $50+ to have it fixed at a mobile repair shop.

So I decided to take a closer look and see if I could figure out the problem. And surprisingly, it was an extremely easy fix which cost less than $1 (assuming you have the required tools)

The culprit, a bad capacitor.


I am not responsible for any damage you may cause to your phone!!! This instructable is meant as a guide only. Disassembling and rework of mobile phone components require a certain level of expertise. If you do not feel comfortable doing this yourself, ask someone who has the skill to help you.

Step 1: Tools Required:

- Torx T6 screwdriver

- Flat head screwdriver

- Pry tool

- Fine tip tweezer

- 10uF 10V non-polar SMD capacitor (size 0603), Ebay link for capacitor

- Hot air soldering tool

- Solder

- Flux paste


If you don't have a pry tool, you can use a nylon RC airplane propeller (even broken they still have a purpose). Just make sure you trim/file off any rough, dents or sharp edges prior to using it.

Step 2: Troubleshooting:

When the battery is inserted in the phone, it should turn on but nothing happens. When the charger cable is connected, the red indicator light on the top right corner lights up after a few seconds, the crossed battery icon pops up.

First thing first, eliminate the main suspect. The battery!

Since it looks like a charging issue, its pretty obvious to test the battery first. My multi-meter read 4.03V which means it is almost fully charged. Mobile phones use Lithium battery which when fully charged would read a voltage of 4.20V.

Suspicion then goes to faulty charger, but upon testing (no pictures of that, sorry) I concluded it was in perfect working condition.

From these 2 tests, we can conclude that there must be an issue with the phone itself.

Time to take it apart, let the fun begin :P

Before disassembling your phone, do a continuity/diode test at the battery terminal of the phone to confirm whether or not there is a short circuit. If your meter indicates no short circuit and you are still getting the crossed battery, it's more than likely its another issue.

Step 3: Disassembling the Phone:

Prior to disassembling your phone, make sure you have the required tools at hand and enough room to work so that you don't lose any screws. Also make sure you have enough time so you don't rush things.

-> Ignore step 6 if you already did a continuity/diode test.

Required tools:

  • T6 torx screwdriver
  • Flat scredriver
  • Pry tool

1. To start with, remove the battery cover and the battery. Lie your phone face down on something soft so you don't scratch the screen.

2. Using the pry tool, remove the rubbery like cover on the bottom thus exposing two screws.

3. You should now see a total of 6 screws, 2 on top, 2 in the center and remaining 2 at the bottom. The top and bottom screws are identical and silver color while the center screws are black and of different length and diameter. Keep the screws safely and remember which goes where (Pretty hard to screw that up!).

4. Remove the top 2 screws, a piece of the front cover (Just above the screen) should come off easily. Remove it and keep it aside.

5. Gently pry open the case with the pry tool starting from the center. The casing on the back side comes off fairly easily. Be careful when removing the front half of the casing as there are some plastic clips holding it in place. Applying sudden or too much force will break them.


Be careful when removing the front half of the case as the track ball may/will fall off.

6. You should now see the motherboard. Before removing the motherboard, I wanted to measure the voltage at the battery terminals with the battery plugged in to eliminate the possibility of a faulty terminal. So put the battery in and measure the voltage at the terminals. To my surprise, my meter read 0.00V which is very weird since off-circuit, the battery was at 4.03V.

0.00V indicates a short circuit and since no magic smoke came out, this suggested (confirmed by a quick google search) the battery has internal short circuit protection.

Doing a continuity/diode test at the battery terminals without the battery confirmed a short circuit (Right there was the AHA moment). This explained everything and also pointed to a likely suspect.

7. We can now proceed with removing the motherboard. First, unplug the keypad ribbon cable using a flat screwdriver.

8. There is a white coaxial wire running from the motherboard up to the antenna on top. Gently unclip it on the antenna side (DO NOT unplug it on the motherboard side). There should be 2 metal brackets holding the wire next to the volume key. Using the flat screwdriver, gently open them just enough to get the wire out.

9. Holding the bottom side of the motherboard, gently lift it up. Underneath are 3 more ribbon cable that you need to unplug. Do so using the flat screwdriver.

10. The motherboard should now be free and can be removed.


You would need to ground yourself before attempting any repair on the motherboard, especially if you have been walking/rubbing your feet on carpet as this would charge up your body with static electricity which you will in turn discharge to the components when you touch them which in turn may damage the latter.

Step 4: Finding the Fault:

With a continuity/diode test, we concluded that there is a short circuit in the power line of the phone. Now comes the daunting task of pin pointing its exact location. Anyone who ever took a look at a motherboard will tell you that its scary with all those components.

Luckily, we can significantly narrow down the search. A power line mainly consists of capacitors, resistors, inductors and some ICs for voltage regulation etc. Each of which is connected in a specific way.

If you ever looked at a power supply schematic, you may have noticed that at the output, there is a capacitor connected across the power rails. That is, one leg is connected to the positive rail while the other is connected to the negative rail. These capacitors are known as filter capacitors and are usually in the microFarad (uF) range. Their purpose is to remove/smooth unwanted ripples in the power line.

In most cases, it is the capacitors that fail and not the resistors. In the event a capacitor fail, it may become internally shorted which would effectively short the power rails. Which is what happened in this case.

Filter capacitors are usually located near the input supply, which in our case is the micro USB port. This gives a location to look at.

NON-POLAR SMD capacitor are 2 pin devices and look like tiny bricks with shiny edges.

To locate a possible shorted capacitor, set you multi-meter to continuity/diode test and measure ACROSSthe capacitors. Poke the capacitors near the microUSB to locate it. The filter capacitor will usually be the biggest among the other neighboring capacitors.

Once you locate the bad capacitor, its time to remove it.

Step 5: Removing the Bad Capacitor:

Desoldering SMD devices is not the same as desoldering through-hole components. Proper care should be taken not to overheat both the component AND the PCB as this will damage them. Exposed to excessive heat, the PCB can/will delaminate which can be seen as a bubble trapped underneath its layers. This in turn may ruin the whole board.

Prior to desoldering anything from the motherboard, make sure to cover any plastic components such as the SIM card module with a piece of kapton tape or a piece of Aluminium to avoid burning/melting them. Second, make sure you mount the PCB level and that the support is not wobbly.

A proper way of desoldering SMD devices is by gradually heating up the PCB or an area around the component to be removed. Start by heating the component to be desoldered from a distance (about 3cm depending on your air flow), and move in a slow circular motion gradually increasing in diameter making sure to heat up the area around the component.

Continue heating in small slow circular motion till the motherboard/area near component is hot enough, use fine tip tweezers to remove the components. If it does not come off easily, heat the PCB more and try again. It will eventually come off. Patience is the key to success.


1. Adding a dab of flux helps.

2. You can use a ceramic tile underneath to protect your table/mat from the hot air.

Step 6: Quick Test:

After removing the bad capacitor, go ahead and do a continuity test at the battery terminals. There should not be any short-circuit. Rather, the multi-meter should read around 1.35V when the positive probe is connected to the positive battery terminal and negative probe to the negative battery terminal.

Reverse the probes (negative probe to positive terminal and positive probe to negative terminal) and try again, this time you should have a reading of around 0.46V.

At this point, you can test if the phone boots up. Connect the ribbon cables back and plug in ONLY the battery. You may leave the track ball disconnected.

Upon inserting the battery, the indicator LED on the top right corner should turn red for about a second followed by the OS loading.


Pay close attention to the polarity when connecting the battery! Accidentally reversing the polarity may destroy your motherboard!

Step 7: Replacing Capacitor:

Once you confirm the phone is working, you can proceed with replacing the capacitor.

You may as well not replace the capacitor but I would not recommend this since it will make your phone more vulnerable to ripple/spikes from your wall charger.

An issue I ran into was that, I did not know the value of the damaged capacitor. But generally, between 10 uF to 100uF capacitors is used for power line filtering.

The only SMD capacitor I had close to the size of the damaged capacitor was size 0805, 4.7uF 50V.

Having something there is better than having nothing. And since there was enough space to safely solder this size, I decided to use it.


Prior to re-soldering the new capacitor, add a tiny bead of solder to the existing solder pad. This can be done with a normal fine soldering iron if you are using solder wire. Else, a tiny drop of solder paste will do.

Add a dab of flux paste to the solder pads and align the new capacitor.

Applying heat is done in the same fashion as desoldering. Take your time and do it right.

After replacing the capacitor, do a continuity/diode test at the battery terminal. If it indicates a short after soldering, you may have created a solder bridge. Add a dab of flux to ease solder flow and reheat the component.

Keep doing continuity/diode test after each reheat to check for solder bridge (short circuit).

Once you are done and there is no short circuit indication, pop in the battery and test the phone.


- Irrespective of the capacitor value you use, make sure its rated at least 10V or above.

- Make sure to clean the motherboard of any residual flux using an electronic grade contact cleaner.

- Make sure the board is dry before connecting the battery or wall charger.

If anyone knows the exact value of the damaged capacitor for this phone model, kindly post in the comment section. Thank you.

Step 8: Reassemble Your Phone and Voila!

Once you are happy with everything, re-assemble your phone. This step is just the reverse of the disassembly process and is pretty straight forward.

Just make sure you do align and plug in the connectors properly. If it does not go in fairly easily, do not exert excessive force. Unclip, align and try again.

Remember to press the metal brackets near the volume keys again to secure the co-axial wire.

Again, do not use excessive force on the plastic parts as they have clips which may break and DO NOT over tighten the screws.

Step 9: Other Issues That Came Up:

Once I was done with replacing the capacitor, there were two other issues I ran into.

First issue:

After the progress bar reached 100% at start-up, I got the 'Reload Software: 507' error message. This is a simple fix as all you need to do is a system restore using Blackberry desktop manager.

When I connected the phone to my laptop, Blackberry desktop manager displayed a communication error message and prompted an update, which I followed. When I clicked 'Get update' however, I got an error message and everything cancels.

So I downloaded and manually flashed the firmware to restore the phone.


Flashing your phone will erase all data.

Second Issue:

After flashing and reassembling the phone, the flash LED would light up upon inserting the battery and stay on even if the phone was turned off. It would stay at around 30-40% brightness.

Turns out it was a bug in the firmware. So I re-flashed the phone with the latest firmware and that did it (after a few hours). After re-flashing the phone, the flash LED would still be on but fluctuating. I left the phone on a table for a few hours and sure enough, it went back to normal.

- Should you have any questions, please feel free to ask.

- Also, suggestions to improving this instructable is the most welcome.

Thank you for taking the time to read.

I hope this instructable helped you guys bring your phone back to life.

Kind Regards,


<p>how to fix 9790?</p>
what is the issue with the phone?
crossed battery icon
<p>Try the troubleshooting steps described in this instructable. If everything checks out, its most probably other damaged components. In that case, I cannot be of much help if I don't have the phone to look at, Sorry.</p>
<p>ok!</p><p>thank you (^O&lt;)</p>
I have no need to fix one of these, but thought I would read anyway. learnt a lot here, very educational. Thanks for taking the time to post this
<p>Thank you very much. I appreciate that.</p>

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