Strange USB power voltage / no midi 3/4

[EsotericLabs]

I was getting irritated for screwing up so many midi 3/4 extensions for my LPC17 MBNG.   Just would not work over and over.  Not even midi out with only two bloody resistors. Quite annoying.

 

But now I found my core is probably running on too high a voltage. instead of 5V it reads 6.5 V  and instead of 3V3 it has 5.04V. It is USB powered from a Mac.

 

Do you think these issues are related?  Adn what to do about them? Thank you!

[Marxon]

Hi!

 

Such high values are desturbing. 

I would first measure the USB port voltage when nothing is connected.

 

Marxon

[EsotericLabs]

with the j17 USB power jumper unconnected, it also reads 6.6V. New powered USB hub?

 

Edit: probably weird volt meter. New duracell 1.5V reads 2.4V   :shocked: :no: Doublecheck tomo.

 

But how many ways can one scr&w up a midi extension??

Edited August 16, 2014 by EsotericLabs

[Marxon]

I meant to measure directly on the Mac USB port. 

If there is really a 6V output then might something wrong with your Mac.

[ilmenator]

There's been an interesting story in one of the last issues of German computer magazine c't about active USB hubs that can damage your computer by violating the specs and feeding current back into the host. Hopefully this is not related.

[EsotericLabs]

Better voltmeter, better readings (5V08 and 3V30) respectively. Sorry for the mess and thank you guys for your assistance!