tl;dr Always test a device before you return it to your customer. It's a good idea to test parts separately (if possible) before installing them. Never apply adhesive before testing a repaired device.

As soon as you receive a part, test it. Don't wait until the part is required for a repair for two reasons.

  1. Return: If an item is in your inventory for several months, it will be harder to return:
    • The part may no longer be returnable under the seller's return policy.
    • The seller may not exist anymore. Many online stores have a short lifespan.
    • If the return is mediated through eBay or elsewhere, the seller has a stronger claim that you may be trying to return a part that you broke or bought from somewhere else.
  2. Ready: The whole purpose of keeping inventory is making sure you're prepared. Simply having a part isn't being prepared. Having a functioning part is being prepared.

Note: always test a device before returning it "fixed" to a customer, even if you tested the parts before installing them. Never apply adhesive before testing the device.

Visual Test ¶ 

Do a visual test for both part quality and part integrity.

  • Part Quality: Are you willing to have your business' quality judged by the quality of this part?
    • For external parts, make sure there are no scuffs, scratches, discolorations, irregularities or other visual defects. The device is precious to your customer, make sure your inventory is perfect.
    • For internal parts, you may be less strict. Some parts (like batteries) may have irregular markings but work perfectly.
  • Part Integrity: Is the part complete?
    • Check all clips, connectors, and fasteners.

Function Test ¶ 

The only way to test the function of a replacement part is to install it and turn the device on. This poses difficulties:

  • If the device's malfunction isn't known, troubleshooting with unverified replacement parts could be a time consuming trial-and-error process.

Make this process easier by testing replacement parts with a device that is known to function properly.

Display Assembly Function Testing ¶ 

Testing replacement display assemblies is not optional. After installation, ensure that:

  1. It powers on.
  2. All pixels function.
  3. The entire touch screen functions.

We accomplish this function test by using a paint app on a verified device. Once the display assembly is installed and the paint application is launched, we select a small paintbrush size and paint over the whole "canvas" with a bright color. The bright color shows which pixels are functioning. And, if any pixels are lit, but weren't painted, it is clear that the unpainted section of the display assembly doesn't have touch functionality.

Test Stations ¶ 

For certain models of smart phones, test cables are available. We suggest that you use a test cable with a dedicated test device if testing a high volume of display assemblies. The internal connectors are fragile and will break with extended use. Similarly, a test cable has fragile connectors that will break with extended use. However, a test cable is much more inexpensive to replace than a working device.

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This test cable is secured to the device with the existing cable bracket.

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A display assembly test station with test cable extension.

Warnings ¶ 

A few warnings for testing replacement parts:

  • It is easier to test replacement parts by leaving the device "open." This is ok, just be extra careful with ESD.
  • If your display assembly doesn't work, how will you know if the device is off? Leave the battery exposed and use a spudger to disconnect the power supply before handling the internal components.

2 Comments

Good list of a straightforward, step-by-step, overall best practices on dealing with new and "to be repaired" components. Next would be the fun part of diagnosis of the "patient" and to do no harm before you know what you are dealing with!

J Brent Masters - Reply

What about testing Screens, Batteries, etc for Mac Laptops?

Gabe - Reply

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