H5 C1 3.3v bus fix

[exxos]

For some bizarre reason, the resistors as highlighted below have been incorrectly fitted as inductors,Not resistors! :roll:

220K.JPG

These need changing with any generic 0805 220K resistors.

The fault is that the 3.3V rail is not actually being regulated by the 3.3V regulator. It is actually being powered from the 5V rail via the GTL buffers which have about 1.5V drop across them. So 5v input gives 5.0v-1.5v = 3.5V. Of course if the 5V is higher or lower, the changes are also reflected on the 3.3V rail. I do not believe it would cause any damage to the 3.3V addon boards. But the buffers are not designed to be used this way and could ultimately damage them.

If you are not using the 3.3V bus then you probably don't need to worry about this fix for now... But I would recommend doing the fix for when the 3.3V addons are released (as you may forget about it in the future otherwise!) .

[Icky]

I have been using the 3V3 bus for a long time on the H5C1 without issue but will replace these sometime this week.