O/C Mastercard - P2 auxiliary connector

[Perik]

Shaun,

While the board is disconnected from both USBMaster and External Power please
check that all pins on U3 have connectivity to where they should.
Use the Ohm-meter and test between U3 – pin 1, 2, 3, 8, 13, 15 & 16
and the same pins on U4 (1 to 1, 2 to 2. etc.). The last to test is U4 pin 14 to U1 pin 7.
Then add your External Power and measure that you have +5V between pin 16 and pin 8 (GND) on U3.
If all OK then add your Expansion and see what's happen.

BTW - Have you verified your DB25 cable between Master and Expansion?

[nolatron]

Just so I have the pin numbering right for U3 and U4;

When looking at the back of the mastercard with the P2 and DB25 ports facing up, Pin 1 would be top row furthest right and Pin 9 bottom row furthest right?

[nolatron]

EDITED:

Got it working. While really checking out the pins on the chips, I discovered a barely visible piece of solder bridging two pin on U3 between the chip and the P2 port. Once I broke that connection, everything is working perfectly now (so far).

Thanks Perik for all your help!

[Perik]

Great Shaun,

As I said - "I'm sure you will succeed"

I don't know how OC do their testing of pre-build cards but this is not good!!
and not the first time. Nice thing though about OC hardware is that you usually can
"walk" into the circuit board. That’s not the case on some of the new hardware
options where a Microscope is a must.

Nice to able to give some "remote" help.