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LED mirror failure due to hight DC voltage

newway

Sep 15, 2019
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Sep 15, 2019
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My wife bought a LED makeup mirror from China, it comes with a 12V DC adapter.
With infinite wisdom, she uses another 24V DC adapter and tries to turn it on - it didn't turn on.
When I discover this and use the original adapter, it won't power on either.

I suspect certain circuit component(s) were damaged, but I have no idea where to start.
This mirror is not available outside China so we can't find a store to return or fix.

I managed to take the mirror apart, in the attached photo is the first circuit board, which I think would be the most likely place if anything's damaged.
Now my question is:
  1. What is this component for? all I know is it takes 12V DC as input.
  2. Which component would be the most likely to be damaged, due to the high voltage?
My wife's really upset and I really want to see if I can fix it, but I have very limited hardware circuit knowledge so any clue would be appreciated! Let me know if you need any information

PS not sure if this helps, when I connect this circuit to the 12DC adapter, the left bottom two components (resistor/capacitor?) gets really hot.

Thank you!

IMG_20190915_210309.jpg
 

73's de Edd

Aug 21, 2015
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3,634
Sir newway . . . . .


Referencing to your picture . . . . .

The adapters power comes into the top connector and then should pass down thru the
boards inline components to the small J1 connector mounted to the side.
Initially unplug the connector, presently plugged into J1, so that no damage can be incurred to its plugged in electronics on downstream .
Then observe that the top J1 terminal will be receiving - incoming power and the bottom will be of the positive power polarity.
Connect a voltmeter set up for DC voltage mode and at a range > than 12 VDC . . .unless its being a smart autoranging unit.
Plug in the CORRECT power adapter and see if there is ~ 12 VDC at those terminals.

You say . . .
PS not sure if this helps, when I connect this circuit to the 12DC adapter, the left bottom two components (resistor/capacitor?) gets really hot.

Is that still the situation, when the J1 is without its loading ?
(That heat presence on the varistor and the in line choke, tells us that the K fuse has not blown . . . . . . . .YET.

VIEWED COMPONENTS . . .
K . . .surface mount fuse 1.5A @ 63 WV
White ceramic monolithic block capacitor
LK . . . . 14V breakdown Vishay Transzorb Varistor
220uh inline choke coil


If so . . . .then . . .we continue . . . . if not . . . . . then you need to get a new wife that is higher on up the intelligentia scale.


73's de Edd . . . . .


By the time you have all the right answers, no one is asking you questions anymore .



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newway

Sep 15, 2019
2
Joined
Sep 15, 2019
Messages
2
Connect a voltmeter set up for DC voltage mode and at a range > than 12 VDC . . .unless its being a smart autoranging unit.
Plug in the CORRECT power adapter and see if there is ~ 12 VDC at those terminals.
.

thanks for your help!
I tried this and No, J1 terminals doesn't yield anywhere close to 12V, it is alternating between 0-1v (without load).
what is this board for? if it supposedly takes 12vdc input and outputs also 12v dc, what is the point?
 

73's de Edd

Aug 21, 2015
3,634
Joined
Aug 21, 2015
Messages
3,634
Sir newway . . . .

what is this board for? if it supposedly takes 12vdc input and outputs also 12v dc, what is the point?

This small board mounts the DC power input jack and fusing and DC surge protection into one select area and then remotes the output to the main board /circuitry.
Some times BAD things can happen to a main board if power connectors are mounted within them, like jerking action actions from drops or pulls and ripping apart the board or connecting parts.

This mechanical isolation procedure keeps the main board protected from such situations and typically access for DC input repair will also be easier access..

WELL NOW . . . . . . if that 12 VDC DC voltage is not present at the J1 connector, lets just go back to its origin at the Wall Wart power supply cube.
Unplug the coaxial end from this power supply board unit and then check at the outer shell and inner contact of that WW's wire ends coaxial connector and see if the 12VDC is even coming in from the Wall Wart.

IF NOT, check your metering to see that you are not erroneously in AC mode instead of DC. If being in DC check out your meter on some 1 1/2 V cells or a 9 V battery or go out and check your car battery at its terminals.

OR . . . . check the other adapter to see if it is putting out its specified 24VDC.

My question left unanswered . . . . . If the wall wart was plugged in as well as J1's connection, you said that 2 parts were getting HOT. ( the Varistor and L1 choke coil ? )
If J1's connection was opened by its unplugging, do those same parts still heat up, or are they cooooool then ?
BTW I can read the white J1 silk screen printing as well as the L1, but what does the hidden area above the LK varistor designate.

73's de Edd

Asking dumb questions is easier than correcting dumb mistakes.


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