General > General Technical Chat
Power adapter advice - Magic smoke from 12V 1.5A portable hard disk
(1/4) > >>
mroguy:
Hi all,
I plugged a 12V 5A power adapter into a portable hard disk which has 12V 1.5A (1.5A) written on the back. It started smoking and is now completely gone.

This was following the advice of a tech guy at my local Apple store who told me that as long as the Voltage matches then there will be no issues. I've seen other posts online that back this up but obviously something has gone wrong here.

Can anyone give crystal clear advice on the rulset for mixing adapters? I've got about 20 portble hard drives and no adapters for them (lost during a home move). Do I need to match the exact Ampage on these as well as the Voltage. Have I just been unlucky here or is there a fixed rulset for this sort of thing.

Hoping some of you guys can advise.

BrokenYugo:
Polarity must match! Not all barrel connectors are wired center positive.
mroguy:
Thanks BrokenYugo. Going to as a dumb question but how do i tell if the adapter polarity matches the hard drive? the 12V has the minus symbol on it. Next to that there are three dots with a +.

Does that help me figure it out?
tooki:
You should find one of the two symbols here:


They need to match on adapter and device.

If an adapter lacks a symbol, it’s easy to measure with a multimeter. Determining what an unmarked device requires can be trickier.
Ian.M:

--- Quote from: BrokenYugo on July 01, 2021, 06:22:00 pm ---Polarity must match! Not all barrel connectors are center positive.

--- End quote ---
*THIS*

However its incredibly annoying when a device has its power requirements marked on it without its DC jack polarity.  In many cases there's an I/O connector somewhere on the device with a nominally grounded shell, so if the DC jack polarity isn't marked its a good idea to test continuity between each contract of the DC jack and the other connector shell.  If there's good continuity, odds are that contact is DC negative.   However if there's any doubt, open up the device and trace the circuit from the DC jack inwards. There's usually a polarized capacitor, an anti-parallel or series diode or an identifiable regulator IC you can look up specs for which will give you the DC jack polarity and even some idea of the operating voltage if the label is missing.

Your portable hard drive may be salvageable - there are often protection diodes that fail shorted if a high current reversed polarity supply is used.  Don't give up on it without investigating it and posting good closeup photos of the damage here.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod