Anker 71an7105 Usb power adapter

[clearchris]

A few years back, I performed a fix where I replaced blown fuses with resettable fuses. So I'm not ready to let this go. https://www.badcaps.net/forum/showthread.php?t=45797

Anyway, usb charger is dead, it won't charge anything. It seems to be something on the high side. Here is what I have done so far.

Removed main transformer to remove the low side from the equation.
Swapped rectifier with a known working one. The original seemed to test ok with diode mode on my meter.
Tested high side mosfet on my lcr-4. Checked ok.
Tested high side diodes on board with main transformer out. Checked ok.
Checked high side cap on lcr-4. Was 10% less than label.

Here's what I observe. With the main transformer, and high side mosfet out, I see 125v AC going into the toroidal transformer (I think that's what it is) that is right before the rectifier. Coming out, I get around 6.5v. On a known working model, it's around 160v-180v AC(can't remember exactly). On the bad model, with the rectifier out, it measures 160-180v. So the toroidal transformer is ok. With a known good rectifier on the bad board, it still measures 6.5v. I have left it plugged in for a while and checked for heat (unplugged), but nothing seems hot. I labeled in the picture where I am measuring.

Anyone have an idea?

[sam_sam_sam]

Re: Anker 71an7105 Usb power adapter

Dose this switching power supply have a ic chip that is a switching power regulator
You will have to look up the ic chip numbers to figure out which it is now more than likely it is on the hot side of the board

I can find it with the picture that you posted

What is the voltage on the optic sensor ic chip on a good one and what is the voltage on the one that does not work correctly

[clearchris]

Re: Anker 71an7105 Usb power adapter

Something just didn't smell right in my testing. Turns out one of my probes was going intermittent. Once I used a new set of probes, I was able to chase it down to this. I'm surprised I was even seeing 6-9v with one of the legs on the toroidal transformer broken off.



I resoldered it, but haven't tested it yet. This looks pretty conclusive though unless I broke it during disassembly.

[sam_sam_sam]

Re: Anker 71an7105 Usb power adapter

You could have but from this picture I kind-a doubt it looks to me either a bad soldering joint that broke loose or could broke when you took apart but if this is case why did it not tare the trace apart

But I could be wrong

[budm]

Re: Anker 71an7105 Usb power adapter

It looks like poor solder works to me, probably that is all wrong with it, I would re-solder all 4 legs of that TOROID, I would also do the same on the other TOROID and the transformer legs as well, just use flux and new lead solder.

[clearchris]

Re: Anker 71an7105 Usb power adapter

Well, the wire actually broke, the other end of the wire was sticking out the opposite side of the board. The toroid was glued in place, but it was probably dropped a few too many times, and the wire broke. This was my wife's travel charger, so I'm sure it was jostled a bit, one too many times apparently. Or it was nicked during installation, and just fully fractured over time. The bend in the wire is pretty strange, that's how I found it.

I reassembled it and tested it, all is good now, so that also eliminates the possibility of my breaking it when I took it apart.

Thanks everyone, the charger lives on!

[ttbloke]

Re: Anker 71an7105 Usb power adapter

Nice one 👍.

I have two of those units and they have been great workhorse family chargers. My units slightly predate Apple 2.4A charging so the smart ICs only give 2.1A max. I fixed this by cutting all the traces from the five smart ICs to the USB data pins, solder-bridging each pair of data pins, and jumpering all five pairs together with 30AWG enameled wire over to to a resistor voltage divider which i soldered in amongst the low side circuitry. (I used 43k Ω to +5v, 49.9k Ω to ground, yields approx 2.7 to 2.8 v). Now the units charges Apple devices such as iPads and newer phones at the full 2.4A / 12W maximum Apple spec for 5v. Android devices still charge too because of the shorted D+/D- pins. Some very old android devices that didn't conform to official USB charging standards would likely still have an issue as a result of the mod (or charge v slowly) eg orig samsung galaxy tabs that wanted +1.25v at each data pin. But we don't have any of those so that “smart” IC isn't needed at all. 👍

I also added a silicon pad / white paste to ensure heat sink plate has direct thermal contact with inside of plastic housing.

[sam_sam_sam]

Re: Anker 71an7105 Usb power adapter

But we don’t have any of those so that “smart” IC isn’t needed at all.

The nice thing about the “smart ic chip “ is that when it works RIGHT it selects the right charger CURRENT for your device but when it does not work correctly it a real pain in the ass

The most reliable setup is the resistor network is still the better choice if the right resistors are chosen

[ttbloke]

Re: Anker 71an7105 Usb power adapter

Agreed. The choice of resistor network has gotten much simpler. If you use the single divider I describe and pipe that 2.8v into shorted D-/D+ pins, 100% of Apple devices will draw their maximum capability, and every Android device I have tested draws their own maximum. In fact, no USB device I’ve ever plugged in - of any type - has ever refused to charge using this scheme. This is all because two critical criteria are simultaneously satisfied:

1) +2.8v is present at both D- and D+ pins, which signals all Apple devices to draw their maximum capable current

2) D- / D+ are shorted together, thus conforming to official USB high current dedicated charging spec

Every USB charger I have purchased that can meet these current levels has been cracked open and modded this way. I’ve been doing this successfully for 7+ years now. Of course this is all going obsolete in the new world of fast charging / USB-C PD etc. And I should point out that the “maximums” I refer to above are all in the context of traditional USB 5v. The actual maximums are obviously higher for fast charging capable devices, which typically seem to employ a higher voltage level than 5v, and perhaps employ additional conductors etc.

[sam_sam_sam]

Re: Anker 71an7105 Usb power adapter

But it is not only the resistor network but also you need to have at least 5.00 volts at device input for this to work

So when you have a 10 foot cord you might have to have 5.25 coming out of charger to over come the voltage loss and on the cable

Here is the type of switching power supply that I use for all of my usb devices

https://www.badcaps.net/forum/showth...t+power+supply