Sometimes you have lightbulb moments, but this was the opposite of that.

My old older son brought this two week old, $25 battery powered USB rechargable desk lamp to me, and complained that it kept turning off.

The Obvious

When I went to confirm that the lamp was plugged in, the Micro-USB port was visibly loose. Not a good sign! These ports often weaken and have poor connector retention, but in this case the entire shroud of the port was wiggling around.

My first instinct was to blame my son for being too forceful, or maybe inserting the connector in upside-down. As it happens though, he wasn’t entirely to blame.

Repairability

4/5 Stars

The hardest part about repairing cheap electronics is generally that they aren’t made to come apart. Thankfully, this unit is held in place with 3 plastic clips around the top of the base. Grabbing the “stem” and pulling widened this crack enough to insert a small plastic cell phone repair pry-bar into the gap and work my way around the top, revealing the following:

Inside, the unit is pretty simple:

An 18650 LiPo battery (or similar), possibly with an integrated protection circuit
A bit of copper tape inside the touch-button, forming a capacitive panel
Two wires running up the lamp to power the LEDs
A length of iron bar as a counterweight
A plastic clip holding the weight and battery in place
The control circuit managing on/off/dimming from the capacitive sensor, a connector for the battery, a charging indicator LED, and the errant micro-usb connector

Pros:

Components are screwed together
Case came apart without breaking entirely
Battery has a connector!

Cons:

It broke!
The copper foil for the touch sensor wasn’t very sticky and fell off after opening. I could see this falling off inside if the unit was dropped. Worse, since it’s copper, it could short the top of the PCB if it was feeling particularly malicious.

The Problem

Once inside, the problem was very clear:

The USB connector had detached from the PCB entirely!

This USB connector is a fairly common design, and while not the most robust in the world, does have 5 flat pins, and two mounting tabs on the sides, which should secure it decently.

Unfortunately, in this case the board designers decided against using the mounting tabs, instead soldering two small globs in the back corners of the connector (not really intended for mounting). On top of that, they only soldered the power and ground pads, despite having pads for all 5, further reducing the physical mounting durability.

These two factors alone shouldn’t have been enough to cause issue, but a third problem pushed this over the edge:

There are two plastic mounting posts at the back of the board, but what’s supporting the front (USB) side? Why, the poorly soldered USB connector of course!

As a result, when the connector is inserted at an ill-advised angle, the pressure is born entirely by 4 solder connections: two cold-solder blobs touching the back of the connector, and two surface mount traces. The blob connections cracked, the traces sheared off, and the USB port was free!

Repair

The repair was simple enough:

Scrape the 5V and Gnd trace solder mask off withing 0.5mm of where the pads sheared off
Use a fine tip iron to tin the newly created pads
Place the USB connector back on the board
Solder the power/ground back in place
Solder the mounting tabs!

Once complete, the unit was quickly re-assembled and fully functional.

Why?

I have absolutely no idea why there isn’t a small ridge under the USB port side of the board to support it. It would easily fit the injection molded part’s mold profile, and this probably wouldn’t happen.

The mounting tabs being ignored is less puzzling. The rest of the PCB only has solder on the top, so they likely didn’t want to add a step to solder the mounting tabs on the bottom after reflow.

That said, the LED and sensor wires are probably hand-soldered, as well as the weird solder blob port mounting bodge, so maybe this was just unclear assembly instructions or the worker taking a shortcut?