EntertainmentCommon

Alarm clock

Also called clock radio, bedside clock.

A small transformer or a capacitive supply, a speaker, buttons, and sometimes a VFD. Capacitive-dropper clocks are not isolated. If you do not see a transformer, treat every wire as mains.

A donor is the dead machine. The parts below are what is still worth removing from it. “Leave it” is a part that is physically in there and should stay in there: too dangerous, too worn, or only useful as part of a repair you are not doing.

What you are looking at

A scrapped machine is a box of parts that failed at different times. The reason it was thrown out is often one bad piece. The motor, the cord, the supply, and the screws are frequently still good. This index says which is which.

Why it is in the trash while the parts are not

The display died, or it was replaced by a phone.

Before you open it

Do this while it is still unplugged, cool, and not leaking. Unplug. Look for a transformer before you touch the board.

Mains voltage

Where the dead machine usually is

Living room and entertainment stack — In the house
Thrift store — Retail
Bulk trash day — Curb

Everywhere.

How it comes apart

Bottom screws. The transformer, if there is one, is the heavy corner.

Tools: Phillips, Meter.

Words on this page

mains: Ordinary household wall power. It can kill. Unplug before you open anything that used it, and do not experiment on live wiring.
isolated: The low-voltage side is not electrically connected to the wall. A proper brick usually is. Many cheap lamp boards are not.
transformer: Two coils on an iron core. It changes voltage and, in a proper one, isolates the output from the wall. Heavy old adapters are this. Microwave oven transformers are a different, dangerous kind.

What to take

The table is the short version. The notes under it describe that part inside this machine, not only the general description.

Parts in this donor
Part	Call	How many	How often	Where to look
Iron transformer	Prize	1	sometimes	Inside older clocks.
Speaker driver	Worth pulling	1	usually	The back.
Tactile switch	Worth pulling	several	usually	The top.
Vacuum fluorescent display	Bonus	1	sometimes	The display.
Indicator LED	Bonus	several	usually	LED-display models.
Switch-mode wall supply	Leave it	1	sometimes	Capacitive dropper supplies.

Prize

Prize — take this firstIron transformer1 · sometimes
Small iron transformer.
Inside older clocks.
Measure it.
Good.

Worth pulling

Worth pullingSpeaker driver1 · usually
Small, for the buzzer.
The back.
Fine.
Good.
Worth pullingTactile switchseveral · usually
Snooze and time-set.
The top.
Keep the board.
Good.

Bonus

Bonus, if you are already in thereVacuum fluorescent display1 · sometimes
Hard to drive off-board.
The display.
With its chip only.
Working and stubborn.
Bonus, if you are already in thereIndicator LEDseveral · usually
Multiplexed digits.
LED-display models.
The digit board is the usable unit.
Good.

Leave it

Leave it — present, not yours to reuseSwitch-mode wall supply1 · sometimes
Not isolated.
Capacitive dropper supplies.
Do not reuse as a bench supply.
Dangerous if misunderstood.