I have soldered a simple adapter to connect my AVRISP mkII to my bradboard.
The AVRISP mkII couldn't communicate with the ATmega on my bradboard. After a while I figured out, that the voltage at the reset pin of the ATmega is only about 3.2 volts. I disconnected the AVRISP and still the voltage was at 3.2V. After plugging out my adapter the voltage was back at 5V.
After inspecting the solder pads and some cleaning (I even used a knife to be sure nothing shorted together) I reconnected the adapter and measured again. The voltage is at about 3.7V.
What is causing the voltage drop? Can the remains of flux conduct?
The picture shows my adapter (back and front) the red line is connected to the reset pin, the blue line to the GND pin.