• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Charging Unit for smartphone - Continuity between + and - ?

Dominover

New Member
I'm currently repairing a charging unit for a Blackview BV6000 smartphone. I'm about to attach a 5 pint Micro USB femal socket to it. The old one wasn't making
contact so it had to go.

On these 5 pin sockets the first pin is + Positive and the last pin is the - Ground. I noticed when I use a continuity tester that there is continuity between the + and Ground terminals where I solder the female connector to. I went ahead and soldered the connector to it anyway (tested all the connections and they contact well) but when I plug in the charger the actual charging unit I plugged the phone into switches off. I feel it may be to do with that continuity between the + and - terminals.

I realise it's probably better to use a multimeter to test resistance between the + and - terminal but I don't have one.. I'm stuck in India due to this pandemic.

Should there be continuity between the + and - terminals even when the socket is not attached? They are all surface mount components by the way.

Any help on this will save my life.. Thanks very much to anyone who can shed some light on this. Diagram below.

5PinMicroUSB.jpg
 

alec_t

Well-Known Member
Most Helpful Member
If you don't have a multimeter how did you detect 'continuity'?
You could expect some finite resistance between pins 1 and 5 (depending on the charger's circuitry), but not 'continuity'.
 

Dominover

New Member
I tested it with a continuity tester. It's just a battery powered light, two rods joined by a wire. The light comes on when I place one rod on the
+ and one rod on the - .

So you say there should not be any continuity between them? There's definitely now solder bridging the gaps so I'm not sure where this continuity is coming from.

Am I interpreting that light wrong?
 

Pommie

Well-Known Member
Most Helpful Member
Your continuity tester is supplying power to the circuit and the bulb indicated it's taking power. Continuity testers are only good for testing conductors, not circuits. AND, if it's a 9V battery it may have destroyed the circuit - and caused it to conduct. Plus, what do you mean by " There's definitely now solder bridging the gaps ", have you shorted the connections?

Mike.
 

Dominover

New Member
Your continuity tester is supplying power to the circuit and the bulb indicated it's taking power. Continuity testers are only good for testing conductors, not circuits. AND, if it's a 9V battery it may have destroyed the circuit - and caused it to conduct. Plus, what do you mean by " There's definitely now solder bridging the gaps ", have you shorted the connections?

Mike.
There's definitely 'NO' solder between the gaps on the circuit board. That's what I meant.. Type The continuity tester is 1.5 volts for a circuit that takes in USB 5 Volts 2 amps approx..

So the fact that the light turns on isn't necessarily a bad thing? Is that the case?
 

alec_t

Well-Known Member
Most Helpful Member
Did you ensure you had the correct polarity (tester +ve to charger +ve) when you used the continuity tester?
If you did, and the light lit, it suggests the charger is faulty and has a short-circuit between pins 1 and 5, i.e there is indeed 'continuity' when there shouldn't be.
 

Dominover

New Member
Did you ensure you had the correct polarity (tester +ve to charger +ve) when you used the continuity tester?
If you did, and the light lit, it suggests the charger is faulty and has a short-circuit between pins 1 and 5, i.e there is indeed 'continuity' when there shouldn't be.
Just to be clear, it's the charging unit which goes inside the phone. It's a separate module inside the phone which has a female micro usb port soldered to it. I was changing the port which is why I have now discovered it.. My charger (the charger I plug into the wall and plug my USB cable into) works fine. It charges other things using the same cables too, but not the phone.. When I take the Micro USB cable and plug it into the wall charger and the other end into the phone, the light on the wall charger turns off. It stops working completely. I gather it's some kind of safety mechanism in the wall charger but is triggered by the charging circuit inside my phone.. Since I've been working on it..

That's why I'm asking about why a continuity tester light comes on when I place one wand on the + and the other on the - terminal in the phone where the micro USB female port is supposed to be soldered to. If I switch the wands around the light still comes on. Current runs both ways it seems.

What does all this tell you? I'm in India right now, stuck here. I took the unit to a professional phone repair place the other day and it was like watching a bunch of 12 year olds tamper with a nuclear bomb. They made me so nervous I just took the part and left. That's why I'm fixing it myself. I've done this kind of thing before.
 

alec_t

Well-Known Member
Most Helpful Member
What does all this tell you?
It tells me (perhaps wrongly) that the module in the phone is faulty and is drawing excessive current which is causing the wall-mount charger to shut down in self-protect mode.
 

gophert

Well-Known Member
Most Helpful Member
Yes, Most chargers (Most good and safe chargers) shut down when the circuit draws too much current.
 

Latest threads

EE World Online Articles

Loading
Top