(true)MIDI USB Board

[estregan]

1. Without PIC18F2550 in the socket and disconnected from the Digital board list all resistances between pin 8 and every other pin of the PIC18F2550 socket.

All resistances between pin 8 and every other pins are indefinitely high except for pin 19, where resistance is 0.

2. Still without PIC18F2550 in the socket, connect Digital board and apply power. List all voltages between pin 8 and every other pin of the PIC18F2550 socket.

All voltage measured between pin 8 and every other pin is 0 except for pin 1, 17, 18 and 20 where voltage is +5.

[dmitri]

1. While disconnected from the Digital board and without PIC18F2550, measure resistance between every pair of pins, i.e. between 1 and 2, 2 and 3, 3 and 4, ..., 27 and 28.

2. Take a picture of the board with PIC18F2550 in the socket. Post it here.

[dmitri]

2. Still without PIC18F2550 in the socket, connect Digital board and apply power. List all voltages between pin 8 and every other pin of the PIC18F2550 socket.

All voltage measured between pin 8 and every other pin is 0 except for pin 1, 17, 18 and 20 where voltage is +5.

There shouldn't be +5 on the pin 17. Mine reads around +1.5V. Check shortcuts on the Digital board between pin 14 of the Atmega32 socket and VCC.

[dmitri]

And also check and list resistances between pin 20 and every other pin of the PIC18F2550 socket without IC in the socket.

[estregan]

1. While disconnected from the Digital board and without PIC18F2550, measure resistance between every pair of pins, i.e. between 1 and 2, 2 and 3, 3 and 4, ..., 27 and 28.

All pairing combinations measure indefinitely high resistance.

2. Take a picture of the board with PIC18F2550 in the socket. Post it here.

Here's the picture of the board with the IC installed.

There shouldn't be +5 on the pin 17. Mine reads around +1.5V. Check shortcuts on the Digital board between pin 14 of the Atmega32 socket and VCC.

We'll get back to you on this, we're investigating further.

And also check and list resistances between pin 20 and every other pin of the PIC18F2550 socket without IC in the socket.

Resistance measured between pin 20 and all other pins is indefinitely high except for pin 1 where resistance is about 3k.

[dmitri]

So, what's up with the pin 17?

[estregan]

So, what's up with the pin 17?

We didn't find any shortcuts in digital board with vcc and pin 14 of atmega32. The only connection to VCC we saw was with R26, which leads me to ask: Should R25 (220) and R26 (4k7) lower the voltage in pin 14? It appears its not lowering the voltage since we still measure +5 on pin 14.

[dmitri]

On the USB board remove R4 and measure voltage on the pin 17 again.

[estregan]

On the USB board remove R4 and measure voltage on the pin 17 again.

Voltage measured is 0.

[dmitri]

1. Disconnect wires 2,3 and 6 of the USBExt connector. Place PIC18F2550 into the socket, power it up. Is the voltage on the pin 14 still not 3.3v? Is the IC still getting hot? If so, go to step 2.
2. Disconnect C4. Measure voltage on the pin 14 again. Is it 3.3V?