Posts Tagged ‘white paper’

Why Wet Cell Phones Cannot be Repaired (Part 2)

Wednesday, February 10th, 2010

We have already outlined in a previous blog post that water / liquid damaged cell phones are beyond economic repair, if repairable at all.  In this follow up we have decided to outline WHY.  Quite simply, the proper procedure is tedious, time consuming and requires replacement of a significant number of parts.  Keep in mind, that while you may only be experiencing a minor issue (a few keys not working), there can be significant additional latent damage that will lead to additional failures over time.  And if this potential for further damage is not taken into account then it shouldn’t be difficult to realize that the phone cannot be truly repaired as any ‘fix’ likely will be only temporary, until the unforeseen damage materializes.  So, we find it unacceptable to consider a liquid damaged cell phone repaired unless it is done correctly by making sure we address not only the obvious but the not-so-obvious damage as well.  To simply ‘fix’ the issue at hand will result in your spending money on a non guaranteed ‘repair’ with a high probability of future failures.  And repair shops that offer or claim to be able repair liquid damaged phones very obviously lack the knowledge and/or don’t understand why the repairs are not economically feasible.  So, let’s examine the process in some detail.

The first step is up to the user: The battery should be removed IMMEDIATELY.  This will minimize the chance for further shorts by removing the primary electrical source.  (It will not eliminate the threat of damage since there will be an internal battery and stored electrical capacity within the circuitry of the phone.)  Users are smart to rely on internet advice about removing the phone’s battery.  However, there are way too many pointless suggestions offered on the internet about how to deal with wet phones, such as heating the phone with a hair dryer to dry it or “Old Wives”  tale  remedies like using rice to absorb the moisture.  It is important for the owner of a water/liquid damaged cell phone to realize that no ‘internet remedy’ will address the core issue of electrical damage to the phone.   The best advice to follow when you have a water/liquid damaged phone is to get it to a qualified repair shop as soon as possible.

Once a damaged cell phone arrives at the shop it needs to be completely disassembled.  The main PCB needs to be inspected for any visible, catastrophic damage such as de-lamination of the PCB layers or burnt areas.  Any damage of this sort is deemed un-repairable.  Once the unit passes initial inspection, the cleaning / repair / testing procedure can begin.

  • The internal battery will be removed and capacitors need to be discharged and / or removed
  • Most vibe motors, speakers, cameras, microphones, shields will be removed.
  • The PCB will be ultrasonically cleaned for several hours in a specialized cleaning solution.
  • The PCB will be rinsed, dried and inspected.
  • Any residue remaining will be hand cleaned.
  • Removed components are re-installed (using new parts for electro mechanical parts – batteries, capacitors, microphones, speakers, cameras, etc to avoid latent failure and reduce the time needed to test each component individually)
  • Each path / circuit (charging, audio, display, etc) on the PCB must be tested for electrical continuity.
  • Breaks in continuity will need to be isolated by testing the path at  various points to isolate the damaged component.
  • The affected component is replaced and the circuit re-tested.
  • The procedure is repeated until all paths are verified.

Then the process is repeated for secondary PCBs.  In many cases, those secondary boards will simply be replaced.  For any clam shell or ‘flip’ phone, the flexible PCBs will also need to be replaced.

As part of the re-assembly procedure, the Liquid Crystal Displays (LCDs) will be replaced.  Most LCDs are now part of an integrated PCB that does not allow for cleaning and testing.  Since there is a high potential failure rate for LCDs once exposed to moisture, failure to replace them will compromise the repair.

When the foregoing has been completed the unit is re-assembled with a new battery.  This is important because batteries are sealed units, with high probability that they short internally once wet. Since a defective battery can damage the newly repaired cell phone it would be pointless to repair the phone and not replace a potentially damaged battery. With a new battery installed the repaired cell phone is put through a series of final tests to ensure correct operation.

Most phones that we have encountered that were exposed to moisture had NOT been submerged, instead coming in contact with a minimal amount of liquid.   This may lead one to believe that it may be possible to forgo a number of the repair steps previously noted, including replacing flex PCBs, LCDs and batteries.  However, liquid is very pervasive and its affects on electronic circuits is very damaging.  Since any portion / component of a phone that comes into contact with liquid needs to be cleaned or replaced to properly repair the cell phone,  even minimal exposure to liquid will require 2 to 3 hours to evaluate, clean and test the phone.  At shop rates of $50 to $75 per hour, very few phones are even worth repairing, fewer still once the cost for parts is added.

Consequently, based on accepting the work that should be done to properly repair a water/liquid damaged cell phone (assuming it can be repaired), it is not economically logical to perform such repairs, and it would be most prudent to be extremely skeptical of any repair shop that offers or claims to be able to do so because it just can’t be justified.

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Wet cell phones CANNOT be (economically) repaired…

Monday, January 4th, 2010

The number of cell phone ‘repair centers’ that claim they can fix liquid damaged cell phones, then claim a 70% or better success rate is truly incredible.  I say this because, in virtually every case, the proper repair of a wet cell phone will almost certainly cost more than the phone’s replacement value. AND, even if it would be cost-efficient (which is not very likely) it is doubtful there are many (if any!!) places that have the capability to even perform the proper repair.

The typical repair service offered by most shops generally starts with a warning to remove your battery immediately and ship in your phone ASAP.  The actual repair consists of dis-assembly, cleaning the printed circuit board (PCB) by hand scrubbing with a brush, using an ultrasonic cleaning filled with isopropyl alcohol as needed, and possibly replacing parts (like displays), and finishing with reassembly.  These phones are then quickly tested, deemed repaired and returned with no warranty.  At best, this is a quick, temporary fix, but no way does it mean the phone has been truly repaired.  How can this be, you may ask.

Your cell phone is a small computer designed around a densely populated central printed circuit board with an integrated LCD display and keyboard.  There may be secondary PCBs as well as flexible PCBs (the flex cables that connect the two halves).  The PCB is, by definition, designed to mechanically support and electrically connect electronic components (resistors, capacitors, radio chips, etc) using conductive pathways, tracks, or traces, etched from copper sheets laminated onto a non-conductive substrate.  (http://en.wikipedia.org/wiki/Printed_circuit_board).

As expected, liquid creates a significant number of issues with the electrical connections throughout the PCB.  The severity of these issues is higher when the liquid involved contains electrically conductive materials, and the greater the quantity of these materials, the more likely, and more / significant, the damage.  Water, soda pop, milk and most other liquids commonly involved in cell phone damage are electrically conductive to some degree.  The conductive nature of these liquids, combined with the moisture, lowers resistance between the electronic components and the underlying circuit paths.  Lower resistance results in high current within the circuit causing a large amount of energy output within a short time frame leading to damaged components.  Additionally, open or short circuits can occur when deposits left on the board result in bridges or unwanted connections between the leads of board components.  In the most extreme cases, this can lead to arcing and fires. (We have quite a few boards displaying such damage.)

So can water damaged cell phones be repaired?  Depending on the liquid, the amount of time the cell phone was in contact with the liquid, and the actions taken immediately following the liquid damage, it is possible.  Is it likely?  No.  Is it cost effective?  Definitely not.

We will continue this discussion in our next post (http://bit.ly/acsmIN), detailing the proper repair procedure and illustrating what is involved, to better be able to understand why it is not cost effective to repair water damaged phones.

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Is your charger failing you?

Monday, November 16th, 2009

One of the biggest issues we see on a daily basis is charging related problems. Normally a cell phone that does not charge or a battery that will not hold a charge.   While a broken charger port is very likely to blame, far too often the port is fine and the issue lies with the charger.  It is important to understand that just because the charger ‘fits’, that does not mean it should be used.

Your cell phone charger is a transformer designed to convert household current to safe levels for charging your cell phone.  On your charger, there is a label containing two sets of figures, one for input and one for output values.  The input values are pretty standard at 100-240v~50/60 Hz. (what the charger can accept from AC current).  The output values, the voltage and amperage, will vary to some degree.  For optimum charging, as well as phone, charger, and battery life, it is important that these numbers match your phone’s charging requirements.

Output voltage – Most cell phones use 3.6 volt to 3.7 volt batteries (fully charged at 4.2 volts).  The charger used must have a voltage output value greater than 4.2 but not significantly higher to avoid damage.  The vast majority of cell phone chargers on the market are generally rated at 5.0 or 5.1 volts.

Output amperage – This indicates the maximum amount of current available from the charger.  Using a charger with an amp output rating lower than required by WILL create a number of issues ranging from very slow charge rates to complete device failure.  The greater the difference between the charger’s output and the cell phone’s need, the greater the risk for catastrophic damage.

Using a charger with a higher amp output is normally safe.  The amp rating indicates, as mentioned, the amount of current available – not the amount of current that WILL be supplied.  If your phone requires 700mA to charge and you use a charger with a 1A output, the phone will draw only up to the 700mA.  The charger simply operates below its maximum limit.  However, failure can still occur.  While cell phones and batteries have internal regulators to protect against overcharging, this protection may be compromised.  Defective or damaged batteries, damage from prior use of low amp chargers, etc. can result in the cell phone drawing excess current if the supply allows it.  The end result can be a burnt main board.

One additional consideration must be given to the charger used – the design of the charge circuit in the phone.  While it would seem acceptable to use a Motorola charger with your Blackberry (interestingly, a vast majority of the Blackberry models we see with charging issues come in with Motorola chargers), as the Blackberry requires 500 to 700mA and Motorola chargers are rated to 850mA, there is an issue as illustrated by a recent repair.  After replacing the charger port on a Blackberry 8320, the phone was reassembled and tested (inadvertently) with a Motorola charger. When the charger was connected, the phone charged successfully.  However, when I went back and connected the 8320 to the Blackberry charger, it failed to charge!  After re-examining the port, I found an open short at one of the soldered connections.  After re-repair, and further testing, the Blackberry worked as expected.

So, while the Motorola charger was safe to use based on its rating, it provided current through a different path than designed.  Depending on the charge path utilized by the Motorola charger and circuit protection through that path, significant damage can occur.

What does all of this mean to you?  Using a low quality, universal, or the wrong high quality charger can lead to poor charging performance, damaged batteries, or permanent damage to your cell phone.  It is the equivalent to replacing the tires on your high performance sports car with ones that have a lower speed rating than recommended just to save a few bucks.  The tires will not last and when they fail, the results could be catastrophic.

Our recommendation – ONLY use the charger designed for your phone by its manufacturer!  Have a Blackberry, use a Blackberry charger.

Not sure if you have the correct charger, give us a shout.  Even if you choose to buy the charger elsewhere, we will happily provide you with the correct part number for the charger you need.

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