[quote]SK1 (top left to bottom right):
3.3 0 0 0 0 0 3.3 0 0.5
0 3.3 3.3 0 0 0 0 1.7 0.1[/quote]
All the voltages are OK except on pin 15 (1.7V), where should be 3.3V and on pin 17 (0.1V), where should be 0.0V.
[quote]The previous voltages are taken again after removing excess flux from the board, which apparently interfered with the measurements.[/quote]If this was the cause of the previous problem, there may still be some remaining flux under the SK1 connector causing some conductivity and pulling the voltage of the pin 15 too low and cause also voltage rise on pin 17, due to possible leakage current.
You may “gently” try to force the pin 15 to higher voltage by following way:
- Solder (about) 10k resistor in parallel with diode D8 on the bottom board.
- Attach the top board and check the voltage on pin 15 of SK1.
If the voltage increases, this may indicate there is still some excess flux on the board.
Also the voltage values when top board detached are all OK except the last one (1.2V), should be about 0.3V.
[quote]SK7 (top left to bottom right):
3.3 3.3 3.3 3.3 3.3 0 3.3 0 0
0 3.3 3.3 3.3 3.3 3.3 0 3.3 1.2[/quote]
Maybe also on this board there is still some flux, but the main cause of the problem may be on the top board.