Please check my logic on Lolin D1 Mini V4 issue

[Peabody]

There's a guy over on the Arduino forum who has a new Lolin D1 Mini V4 which he bought directly from the Lolin store on Aliexpress.  The problem is - when he powers with 5V from USB or from the 5V pin, he gets 5V on the 3.3V pin.

https://forum.arduino.cc/t/wemos-d1-mini-high-consumption-in-deep-sleep/977126/20

I've given him advice on what he might do to find the cause of the problem, which is to desolder and lift the output pin of the "3.3V" voltage regulator.  If he still gets any voltage on the 3.3V pin, then the problem is not the regulator, and there must be a solder blob, or perhaps even a wrongly-placed trace, which feeds 5V to the 3.3V rail.  The same would be the case if the voltage on the lifted output pin is now 3.3V - the regulator is fine, but something else is wrong on the board.  He would then check for continuity between the 5V and 3.3V pins, and try to locate where the bridge is.

But if the lifted output pin measures 5V, then either it has failed short (input to output), or they populated a 5V regulator instead of the correct 3.3V version.  From what I can tell, markings don't say what you have.  The regulator is the ME6211.  To distinguish between these last two situations, I would apply 7V, or a 9V battery, to the 5V pin.  If the ouput pin goes up to 7V or 9V, then the regulator has shorted.  But if it stays at 5V, then the regulator is good, but they put in the wrong regulator.

Does this make sense, or is there a better way to find out what's going on?  Does anyone know of a reason why it would be appropriate to apply 5V to an ESP8266?  Also, the Mini seems to actually work at 5V.  Is that typical?  I see nothing in the datsheet suggesting that is permitted.  Would this be a chip you would trust in the future having been run at 5V?

I have an earlier version, but not a V4.  Is there any chance all the V4s are like this? Anybody have one on hand that they could check?

[thm_w]

A lot of people have run the ESP8266 at 5V without issues: https://hackaday.com/2016/07/28/ask-hackaday-is-the-esp8266-5v-tolerant/
Probably gets a bit hotter though.

What you suggest makes sense, if they have soldering ability. They could also try probing for shorts with a multimeter.

[Peabody]

Thanks very much.  But this is not just hitting the GPIO pins with 5V.  This is running the 8266 on 5V on its Vcc pin(s).  And the flash chip as well.  The entire 3.3V net on the module is at 5V.  That's a bit different from "5V tolerant" IO pins.

[thm_w]

Thanks very much.  But this is not just hitting the GPIO pins with 5V.  This is running the 8266 on 5V on its Vcc pin(s).  And the flash chip as well.  The entire 3.3V net on the module is at 5V.  That's a bit different from "5V tolerant" IO pins.

Read the comments in the link:

TacticalNinja says:   
July 28, 2016 at 10:47 am

I agree, however I had a bunch of 8266’s that survived being connected to 5v. Not a single one burned. I noticed that the temperature difference when running with 3.3v is not significant than with 5v.