EUROCOM 780W AC ADAPTER - 0.0V problem fixed

[Teo]

[PLEASE WORK WITH CAUTION] ⚠️ HIGH CURRENT IS STORAGE ON CAPACITORS

 

Hello everyone 

(Sorry for my poor English)

 

This is just a small walkthrough of how I fixed an issue with the EUROCOM 780W AC ADAPTER when it was not supplying power to the laptop and showed only 0.0V on the display. It was really frustrating and confusing why it didn’t have any power. This problem it didn’t appear right away, it did start happening slowly, some days it was just fine supplying 20v and some days I had to turn it off for few minutes and then turn it on back and it was fine until the problem became so persistent that it was not supplying power at all, just showed 0.0V.

 

At first I thought it was a ground issue, I used to have a Clevo P775TM where the Ac Adapter wouldn’t work if wasn't grounded. 
 

Next I thought it was an ID pin issue, but on these laptops or on my case (CLEVO X170KM) they don’t seem to have an ID pin, I had measured every pin on the connector and there isn’t any ID pin, just + and - as far as I know. 
 

So next was to open the AC ADAPTER itself.

first I headed for the MOSFETS, I thought something was not switching there or some IC chip was not sending the signal. 

Checked every single mosfet that I saw was hotter than usual thinking could have gotten shorted. None of them was faulty, next I checked all the coils and they were fine, not blow up or with lower capacitance. 
 

So last it lead me to the resistors, as I know for some experience the resistors helps to measure if voltage is passing (Sensor Resistors) or also to regulate voltage, pull down.

 

 

I headed to the resistors that is connected directly to the output. 
 

On my view these resistors were the one doing part of the heavy lifting so I went ahead and measured them out of the board, (while soldered into the board there was not proper reading).

 

 

For my surprise there were more than 4 resistors with low ohms, not too big of a difference but it already crossed the ratio limit. -5k is a lot and some around -10k, I believe the IC power controller it was stopping the AC ADAPTER to output that low voltage. 

 

(You can see 6x 1206 resistors on the upper part of the picture - those were fine - and 6x 1206 more at the middle, 4 having low resistance.)

 

After replacing one resistor the “9103” =910K ohms (dimension= 1206 for reference) with 1M ohms resistor (the closest I had at hand) the AC ADAPTER supplied 20.1v and it was working normally, not problem whatsoever. 
 

 

If you have this issue please replace the resistors with the same capacity, don’t do like I did, is a bit higher but I intend to replace it with right resistance when I get them. 
 

[PLEASE WORK WITH CAUTION ⚠️ HIGH CURRENT IS STORAGE ON CAPACITORS.]
 

All the best.