Oscillating voltage 0-2-0

Thread Starter

aditz

Joined Dec 13, 2016
5
Hello

I have a device that stopped working suddenly. Now the voltage required by it is not constant anymore. It is just 0V, 2V, 0V and so on, changing every second. Could anyone guide me into finding the cause of it?

Thank you!
 

Thread Starter

aditz

Joined Dec 13, 2016
5
The device is an iPad. I have a small device that reads the required voltage in series with the usb cable (charger->voltage read device->usb cable->ipad) and this is how I saw the "anomaly". I am a beginner in electronics and I don't know the terms so good. I was curios what component can cause this oscillating behavior.
 

AlbertHall

Joined Jun 4, 2014
12,345
Does the iPad fail to charge properly? Does the iPad, in other respects, work correctly?
The charger should provide a fixed voltage which should be 5V if it is USB. It is possible that the iPad is faulty and drawing too much current and so dragging the charger output down. It is also possible that the charger is faulty and is failing to provide the correct voltage. I guess it is also possible that it is the voltage measurement part is faulty.
To decide which is happening you need to either use a different charger or a different iPad.
 

Thread Starter

aditz

Joined Dec 13, 2016
5
Thank you for your reply.
The charger is tested on another ipad and works good.
The part with "drawing too much current" is interesting. Could you please give me more details? Should I go to the ipad's mainboard to check for something? What can cause this power draw? ICs or caps?
 

AlbertHall

Joined Jun 4, 2014
12,345
Thank you for your reply.
The charger is tested on another ipad and works good.
The part with "drawing too much current" is interesting. Could you please give me more details? Should I go to the ipad's mainboard to check for something? What can cause this power draw? ICs or caps?
When the charger was tested on the other iPad, was the voltage measurement gadget in circuit, and what reading did you get?
Does the 'problem' iPad charge from the 'problem' charger? If not, then does it charge properly without the voltage measurement device?
Does the 'problem' iPad charge from a different charger?
 

Thread Starter

aditz

Joined Dec 13, 2016
5
Yes, the gadget was also in series when I tested the other ipad. It was 4.9V, so let's assume 5 because of small error in reading.
I tested the problem ipad without the gadget and it does not charge/display anything at all.
There is no problem charger. The same charger works on the good ipad, but doesnt charge the problem ipad.
I also tested the problem ipad with another new charger and still doesn't charge. Exactly the same behavior like with the first charger.
 

AlbertHall

Joined Jun 4, 2014
12,345
So the iPad is defunct. It may be the battery (I don't know whether a defective battery can do this or not) so it would be worth checking this iPad with a battery from a working iPad to eliminate (or confirm) the battery.
 

Thread Starter

aditz

Joined Dec 13, 2016
5
I will check this. Thank you very much. As a side topic: what could cause this intermittent voltage up/down, besides the battery?
 

AlbertHall

Joined Jun 4, 2014
12,345
I will check this. Thank you very much. As a side topic: what could cause this intermittent voltage up/down, besides the battery?
I don't know that the battery can cause this. Suggesting any possible cause, based on present information, can be only wild guesses.
 

hp1729

Joined Nov 23, 2015
2,304
Hello

I have a device that stopped working suddenly. Now the voltage required by it is not constant anymore. It is just 0V, 2V, 0V and so on, changing every second. Could anyone guide me into finding the cause of it?

Thank you!
Most likely a capacitor causing an over current condition. It goes into over current and shuts down. When it shuts down the over current goes away and it tries to turn on again. Goes into over current ...

You can get a USB test fixture that monitors voltage and current. Electronic Goldmine sells two types. G21171 and G21309. About $5 to $10 as I recall.
 

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JUNELER

Joined Jul 13, 2015
183
Hi,
intermittent voltage up/down is a sign of having a a problem in a circuit either partially over voltage or
over current that was detected by the circuit of fully controlled output, to protect to totally damaged
the charger device in used.Also the Ipad itself had the same circuitry to do the same thing as the charger.

Since you are starting to isolate one at a time by swapping the battery / ipad or charger to working one,
this is called elimination technique or process doing by all technicians or engineer.
 
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