Wire & connectorsRebuild shelfHand tools, works as-is

USB cable

Also called USB-A, USB-C lead, charging cable.

A power cord for 5 V, until it is a data cable, until it is a USB-C cable that does not have the data pairs or the e-marker you assumed. The failures are at the strain relief. Cut the plug off a tired cable and you still have wire; you do not have a reliable data cable.

If you are new to this category

Wire and plugs are how power and signals move. The insulation is the safety, not the copper. Ethernet cable is fine for small signals and low voltage. It is not a substitute for a power cord. A connector you can unplug is worth more than a wire you have to solder every time.

Match the plug that came with the brick. Center-positive is common and not universal. The drawing on the label is a map: the dot is the center, the ring is the outside.

Center pin and outside sleeve

The drawing on the brick is the polarity. A dot inside a C-shaped ring means the center is positive when the plus sign points at the dot. Measure anyway. The two common hole sizes, 2.1 mm and 2.5 mm, almost fit each other and that is how the center pin gets bent.

Specification. The right-hand column is what is typical. The label on the part in your hand wins if they disagree.
What to look for	Usual figure
Power	Thin charge cables may be 28 AWG and get warm above an amp. A cable that charged a phone is not a 5 A cable.
USB-C	Some are power-only. Some are USB 2. Some negotiate 20 V only if both ends and the e-marker agree. Do not use a random C-to-C lead as a 20 V patch cord.
Colors	Red 5 V, black ground, green and white data, when anyone followed the convention. Confirm.

Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.

What people actually use it for

5 V distribution
A short data lead you have actually tested
Scrap copper and a connector

Leave this one when

Intermittent when wiggled. That is the whole failure mode of this part.

Buying a new one is the better idea when

A known-good data cable. This is not a part to be romantic about.

How to tell if this one still works

Load it. A cable that is 5.1 V unloaded and 4.4 V at 1 A is a heater, not a cable. Data: plug it into something that enumerates.

Tools you will want: Meter, A load.

Where people actually find it

7 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.

Harvest at a glance
From	Call	How many	How often	Where it sits
Optical mouse	Worth it	1	usually	Out the front.
Keyboard	Worth it	1	usually	Fixed or detachable.
Webcam	Worth it	1	always	Fixed cable.
Barcode scanner	Worth it	1	usually	Fixed or coiled.
Wall adapter	Worth it	1	sometimes	Fixed USB chargers.
Game controller	Bonus	1	sometimes	Wired pads.
Power strip	Bonus	1	sometimes	USB-outlet versions.

Worth pullingOptical mouse1 · usually
In this particular machine
USB-A. The failure is usually the first 50 mm.
Where to look
Out the front.
How to get it out
Cut off the frayed end and you still have a short cable, after you test it.
The condition to expect
Test under flex.
Worth pullingKeyboard1 · usually
In this particular machine
Detachable USB-C or mini-USB cables are the better prize.
Where to look
Fixed or detachable.
How to get it out
Unplug a detachable one. A fixed cable is ordinary USB.
The condition to expect
Good if it is not intermittent.
Worth pullingWebcam1 · always
In this particular machine
USB-A.
Where to look
Fixed cable.
How to get it out
The strain relief is the failure point.
The condition to expect
Test it.
Worth pullingBarcode scanner1 · usually
In this particular machine
Sometimes a replaceable cable.
Where to look
Fixed or coiled.
How to get it out
Test under flex.
The condition to expect
Coiled leads break at the ends.
Worth pullingWall adapter1 · sometimes
In this particular machine
Often power-only.
Where to look
Fixed USB chargers.
How to get it out
Load-test it.
The condition to expect
Fine.
Bonus, if you are already in thereGame controller1 · sometimes
In this particular machine
USB.
Where to look
Wired pads.
How to get it out
Test it.
The condition to expect
Fine.
Bonus, if you are already in therePower strip1 · sometimes
In this particular machine
A small 5 V supply inside.
Where to look
USB-outlet versions.
How to get it out
That supply is the interesting part. Isolation-check it.
The condition to expect
Mixed.