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[Somewhat solved] NES outputs 4.6V on controller port instead of 5V which prevents Blueretro from functioning properly (jlai.lu)

submitted 5 months ago* (last edited 5 months ago) by [email protected] to c/[email protected]

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EDIT: Thanks everyone for you help, that has been very instructive. I think I just have a very poor quality cable adapter. Given that Blueretro is mostly an opensource DIY project, I’ll make a cable adapter myself instead of trying to fix what would obviously not function properly.

Hi everyone,

First of all let me say that I’m a total noob in electronics (I really only know the basics) and I’m facing an issue that I really don’t know how to tackle.

I have bought a Blueretro NES adapter on Aliexpress (this one) and it does behave erratically when powered by the console alone (Bluetooth not working, LED indicator down, random outputs to the console).

When I’m powering via USB, everything function properly.

So I guessed that I might have a voltage issue on the NES side. I tested mine and make a few friend test theirs (5 in total including mine) and the result is still the same: the controller ports outputs between 4.6 and 4.8V instead of 5V.

The Blueretro itself apparently uses an AMS1117 (picture here) which, from my understanding, is stepping down 5V to 3.3V (wild guess, I don’t really know what it does, just quickly read the datasheet).

So, sorry for the long intro, here are my questions:

Is it wise to try to step up the voltage from the NES to the Blueretro from 4.6V to 5V? How would it be possible? Is it even possible?
Given that the Blueretro is taking 3.3V apparently, is it possible to step down from 4.6V to 3.3V instead? Is it wiser than stepping up?

Thanks in advance and sorry for the long post :)

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[–] [email protected] 3 points 5 months ago* (last edited 5 months ago) (1 children)

What I’ve measured so far:

from the controller port directly: 4.8V
from the wires inside the adapter without Blueretro attached: 4.6V
from the wires inside the adapter with Blueretro attached: 3.9V

There are some active components inside the adapter itself, I guess this could explain the drop 0.2V drop.

So is it sagging?

[–] [email protected] 2 points 5 months ago (1 children)

The 74AHCT125N appears to be a 3v to 5v level shifter, which I wouldn't expect to be drawing a lot of current. So if just the adapter's presence is causing 0.2v drop, then yeah, that would suggest the output current of the port's voltage rail isn't very high, causing substantial sag.

To be abundantly clear, is the Blueretro meant to work when only powered by the console? It certainly wouldn't be as convenient -- an extra cable and power block to deal with -- but everything is functional when externally powered by USB, yes?

Do I understand that your original post is debugging why the console isn't sufficient to power the Blueretro?

[–] [email protected] 2 points 5 months ago* (last edited 5 months ago)

The 74AHCT125N appears to be a 3v to 5v level shifter

I don’t think the cable adapter is using this particular chip. I see two much smaller ones. Maybe that’s the issue.

To be abundantly clear, is the Blueretro meant to work when only powered by the console? It certainly wouldn’t be as convenient – an extra cable and power block to deal with – but everything is functional when externally powered by USB, yes?

That’s right Blueretro is supposed to be powered by the console alone. When powerd by USB, it is perfectly functional.

Do I understand that your original post is debugging why the console isn’t sufficient to power the Blueretro?

That’s correct.