I built another batch of Junebugs and all worked but one.
I washed the backside of the PCB with flux cleaner.
You can see parts of the PCB at http://www.rocklore.com/3v0/jbp/
VPP is fine (reports 11.9V) without a processor in the target socket.
With a processor and all switches open reported VPP drops to 8.1.
With a processor and switch positions 1-3 closed a short is reported.
VUSB is 4.85 with and without the target chip.
Target pin 1 connects to the charlieplexed LEDs. On a working Junebug without a target processor this pin to gnd is an open circuit. With this unit is shows 2.6K to gnd.
I can not think of a logical reason for VPP to drop with the processor installed and the switches open.
My DVM reads a bit on the low side so 11.9 could be 12 and 4.85 could be very close to 5.
3v0
I washed the backside of the PCB with flux cleaner.
You can see parts of the PCB at http://www.rocklore.com/3v0/jbp/
VPP is fine (reports 11.9V) without a processor in the target socket.
With a processor and all switches open reported VPP drops to 8.1.
With a processor and switch positions 1-3 closed a short is reported.
VUSB is 4.85 with and without the target chip.
Target pin 1 connects to the charlieplexed LEDs. On a working Junebug without a target processor this pin to gnd is an open circuit. With this unit is shows 2.6K to gnd.
I can not think of a logical reason for VPP to drop with the processor installed and the switches open.
My DVM reads a bit on the low side so 11.9 could be 12 and 4.85 could be very close to 5.
3v0