Harald,
Yes, the error is on the SBC v2 schematic for the Molex connector part.
Pins 1 and 4 are reversed.
The best way to be sure you have the right connection is to look at how
the PC power supply mates with the on-board connector. The confusion
lies in the pin numbering, so forget pin numbering entirely. Consider
that the Molex connector has two inner pins, and two outer pins:
** The red wire, +5, should go to the outer pad that powers the board.
Look at the bottom trace on the SBC card.
** The yellow wire, +12, should go the the outer pad that is not
connected anywhere.
** The two black wires, grounds, should connect to the two inner pads.
If you carefully followed the pin connections for mounting the Molex
connector to the SBC v2, there is a possibility that it is mounted
backwards from the way it needs to be. Unfortunately, this has happened
to a couple of builders. This error persisted for 2-3 years before
anyone caught it. It propagated from the SBCv1 to the SBCv2 to the
SBC-188v1 before it was noticed earlier this year.
I know the error is corrected on the SBC-188v2 (just back from
fabrication). I think the latest production run of the SBCv2 corrects
the error. I would have to see photos of the top and bottom of your
board in the area of the Molex connector to tell you whether you have
the error or not.
Just make sure you connect the red wire to the Molex pin that powers pin
14 (or 16) of most of the DIPs on the board. That is +5v.
--John
BTW: If you cut the yellow wire so it cannot connect to the SBCv2, you
can never burn the board. If +5 (red) connects to the wrong pin, you
will have an SBC that is not powered. The downside of doing this is you
will have compromised one connector on your PC power supply.
Post by Harald RauHello,
Thank you for your support, but I'm a little confused.
In the sbcv2 SBC-schematic PDF is PIN 1 +5V to PIN 2 and 3 at GND. PIN
4 is not connected! [see powersupply.jpg]
But i have a power supply for a external HD with a 4-pin Molex
connector. I have +12V between PIN 1 and 3? [see 1-3.jpg]
So i have +5V between PIN 4 and 2? [see 4-2.jpg]
Is the number on the plug wrong?
Thank you and greeting!
Harald!
Harald,
The 4-pin Molex connector on the N8VEM SBC's (all of them) was used with
PC power supplies in mind.
wire 1 is yellow, +12, and connects nowhere
wires 2&3, the middle wires, are black == GND
wire 4 is red, +5v, and powers the board
Due to an error in SBC board pad numbering, the +5 may connect to either
a square pad (older board) or a round pad (newer board). The +12,
similarly, may connect to either a round pad (older board) or a square
pad (newer board).
What matters is that the red wire powers the board, and the yellow wire
attaches to the pad that is not connected.
=============================================
The only problem you might have with a PC power supply is that the +5
load may not be great enough to allow the switching supply to turn on.
Some power supplies require a minimum load.
--John
Post by Harald RauHello,
How the power supply works?
Can i use from the PC power supply the plug for the hard drive
without
Post by Harald Rauchanges.
How many volts are between pins 1-4
In this photo works a PC power supply, is that correct?
http://n8vem-sbc.pbworks.com/w/file/fetch/39997419/2011-05-09%20SBC%20V2%20with%20Power%20Supply.JPG
Post by Harald RauGreetings Harald!
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