Recently I was repairing a USB charger (a six-output power supply) that was theoretically supposed to provide up to 6 amps at 5 volts (30W).
I repaired the power supply, but once it was repaired, it would not deliver 6 amps and as soon as the consumption got close to 2 amps the output would cut off.
I am writing this post as a complement to the video I posted on YouTube with the repair, to expand on the information and to leave some additional thoughts and notes.
I recommend that you first watch the repair video (if you haven't already).
Making these videos takes a lot of work. If you like the video don't forget to like and subscribe to the channel. That will motivate me to keep making more videos like these.
- 1 Symptoms
- 2 Diagnosis
- 3 Repair
- 4 Results
- 5 The surprise: when is 30W power adaptor not a 30W power adaptor?
- 6 The truth of the "30W 6A" USB charger
- 7 Material used in the repair of the USB charger
The power supply worked well for several years, with several devices permanently connected to it 24 hours a day, although none of them really consumed too much (I estimate that with everything connected, the power consumption must have been between 1 and 1.5 amps).
One day the power supply simply stopped working. There was no voltage at the output. I had to get on with repairing the USB charger.
I measured the output of the power supply and it was: no load (nothing connected), 5.04V, which is correct, but when I connected anything it turned off (I tested it with a 1A load), interrupting the output and turning off the power indicator LED.
The first thing I did was to open the power supply, to access the board, and make a detailed visual inspection. Often the failure in this type of device can be seen with the naked eye (inflated electrolytic capacitors, burnt or exploded components, overheating marks, etc.).
There was nothing obvious that could indicate what the problem was, so I moved on to the measurement stage.
For the repair of the USB charger, I was going to focus on the electrolytic capacitors in the low voltage area, as experience showed me that they were the most prone to cause a failure like this.
Indeed, the three capacitors had a very high Equivalent Series Resistance (ESR) and had lost part of their capacitance.
The first one had an ESR of about 6Ω, the second one about 8Ω and the third one 2.5Ω.
In this table you can see typical values for electrolytic capacitors of different capacitance and voltage:
These 470µF, 10V capacitors should be about 0.42Ω.
The repair of the USB charger consisted of replacing the three capacitors with new ones of the same value.
The capacitors I put in had an ESR of about 0.7Ω but I took them for good, as they are cheap Chinese capacitors, bought on AliExpress and you can't expect much from them either.
A capacitor is usually said to be in poor condition when its ESR is more than twice its typical value.
Once the repair had been carried out, it was time to check the results and to consider it good or not.
The first check showed us that the power supply, at no load, gave us 5.03V, which is correct.
The next check was to connect a load (the same 1A load we had used before) to see if it was still working properly.
Indeed, with a load of 1A at the output it still worked, with an output voltage of 5.05V.
The next test? Try it with higher consumptions?
When I tried 3A, the source would immediately shut down.
I repeated the attempt with 2A and it also shut down....
Should I take the repair for good or not? I decided to leave it for a while and think...
The surprise: when is 30W power adaptor not a 30W power adaptor?
Not satisfied with the result, I started to investigate, and found the following...
The THX203H integrated circuit
First, I checked the datasheet of the THX203H integrated circuit, which is the IC used by the power supply. It was not difficult to find it.
The first surprise was to find that this IC is capable of providing a maximum of 12W continuous and 18W peak. This means that at 5V it provides a maximum 2.4A with peaks of 3.6A.
How had I been sold a 30W power supply which used a controller that could give a maximum of 12W?
Did the power supply have "something" extra that made it able to deliver 30W?
Schematic diagram of the power supply board
In order to easily check if the board had "something" that allowed it to give the 30W, without spending a lot of time analysing each component of the board, I tried to locate the electronic schematic and, although I didn't find the exact schematic of this board (which is marked WA9003-AD0G), I found the WAA020 board schematicwhich is very similar and which a person called Rindeal (Jan Chren) had been kind enough to reverse engineer.
There was nothing in the schematic to increase the power output, but I found something interesting: this power supply, which was almost the same, and which also used the THX203H controller, was declared to be of 5V and 1.5A
The WA9003-AD0G board
So I went looking for the board... and found it.
Several sellers on AliExpress had this board for sale, for example these two:
AC-DC switching power supply module, 5V, 2A, 2000Ma switch, for replacing/repairing LED power supply board
AC-DC-switching power supply module, short-circuit, over-voltage, over-current protection, AC 100V-240V to DC 5V 2A
It is certainly incredible that these power supplies cost less than 1€ (plus shipping costs, which are also cheap).
I want to make one thing clear: in my opinion these power supplies are not bad, on the contrary, I think they are quite well built (especially compared to many "2A chargers" I have seen around...) the problem, and what I am criticising here, is not the board or its manufacturer, but the manufacturer of the charger, who is deceiving us.
The truth of the "30W 6A" USB charger
Made up his mind, once the USB charger repair was done, that I had been cheatedI decided to treat it as a "normal" charger (around 1.5A or 2A) and tested again.
In this case, what I wanted to know was how many amps it could actually supply.
For the new tests, I used an EDB-USB+ electronic load to be able to analyse more easily and to get some graphs by connecting it to the PC.
In this way I could clearly see that the power supply performs perfectly up to almost 2A consumption, as you can see in the graph below.
In the light of the above, what we can say is that:
- We are being deceived by selling us this power supply/charger as being capable of supplying 30W 6A, they should be selling it as 1.5A (or 2A in the most optimistic case).
- That said, the charger is not bad and, if we had been told the truth, it would be a recommended purchase..
Material used in the repair of the USB charger
For this repair I used the following material:
👉 Soldering iron TS101 (in the video I use an older model, the TS100)
👉 TC1 Component Tester (a must in any workshop)
👉 USB Tester FNB58 (similar to mine, which can no longer be found, but much better)