Bryan Mayland
TVWBB Hall of Fame
As discovered in the From and for an electronics newbie thread, the v4.1 boards that have been out for a while have an error in the board file which prevents the LED1 (the lower one) from lighting.
The problem is that the trace doesn't reach the ATmega pin
If you have an existing v4.1 board, you can fix this by running a small wire to replace it, as shown here by Steve_M.
Board file is updated with the LED1 trace fixed. Pushed to github, shared on OSHPark and updated capnbry.net's HeaterMeter PCB.
I also nudged the 5V regulator up 0.01" to allow the ground plane trace to reach it directly. This may alleviate the need for the "white wire" ground fix.
The problem is that the trace doesn't reach the ATmega pin

If you have an existing v4.1 board, you can fix this by running a small wire to replace it, as shown here by Steve_M.

Board file is updated with the LED1 trace fixed. Pushed to github, shared on OSHPark and updated capnbry.net's HeaterMeter PCB.
I also nudged the 5V regulator up 0.01" to allow the ground plane trace to reach it directly. This may alleviate the need for the "white wire" ground fix.