(true)MIDI USB Board

[dmitri]

Also, are you connecting USB and serial cable to the same computer? Since all wires, except Ground, on the serial port connected over 10k resistors, they cannot cause high current and so cannot cause IC to get hot. I can only suspect that ground, pin5 on DB9, is not properly wired.

[estregan]

Also, are you connecting USB and serial cable to the same computer? Since all wires, except Ground, on the serial port connected over 10k resistors, they cannot cause high current and so cannot cause IC to get hot. I can only suspect that ground, pin5 on DB9, is not properly wired.

Yes, we're connecting the USB and serial cable to the same computer. We'll investigate further and report back. Thanks for the quick answers as always.

Edit: Tested the board for shorts or open lines but found none, all wiring seems correct. I also tried connecting only the USB cable and the IC immediately got hot. Any ideas why this would happen without the ICSP cable connected to the computer and the board? Will post pictures of the board and the cable later.

[Marctwo]

I'm assuming that you're using a JDM type programmer. This shouldn't be connected at the same time as the USB as it does magical things in order to deliver 13v to MCLR from the +12v/-12v lines. Having done this already, you may well have blown a componant or 2 on your board/programmer/com port.

As your board is now overheating with just USB connection, I'd guess that you've blown a capacitor or something that's now creating a short. I think you're best to check all componats for faults before continuing.

In programming similar chips I've found PicPgm to be the most reliable software.

[dmitri]

I'm assuming that you're using a JDM type programmer. This shouldn't be connected at the same time as the USB as it does magical things in order to deliver 13v to MCLR from the +12v/-12v lines. Having done this already, you may well have blown a componant or 2 on your board/programmer/com port.

As your board is now overheating with just USB connection, I'd guess that you've blown a capacitor or something that's now creating a short. I think you're best to check all componats for faults before continuing.

In programming similar chips I've found PicPgm to be the most reliable software.

Wrong assumption so the explanation/suggestion is wrong.
You can, and actually must, connect both USB(to provide +5 to PIC18F2550) cable to an USB port and ICSP cable(shown on the Schematics page) to a serial port of the same computer at the same time so that the ground of both USB and ICSP (serial) cables were of a common origin. Even though you select JDM programmer in WinPic, you don't actually use a JDM programmer and PIC18F2550 is programmed using LVP (low voltage programming) mode.

I suggest you to keep looking for a mistake in your board: pins 8 and 19 on PIC18F2550 are ground pins (zero Ohm resistance between Digital board ground and these pins) and pin 20 is Vdd - you should read +5 between ground and this pin when power is applied to MegaDrum. Check if you inserted PIC18F2550 correctly into a socket, i.e. didn't turn it 180 degrees.

[estregan]

Wrong assumption so the explanation/suggestion is wrong.
You can, and actually must, connect both USB(to provide +5 to PIC18F2550) cable to an USB port and ICSP cable(shown on the Schematics page) to a serial port of the same computer at the same time so that the ground of both USB and ICSP (serial) cables were of a common origin. Even though you select JDM programmer in WinPic, you don't actually use a JDM programmer and PIC18F2550 is programmed using LVP (low voltage programming) mode.

I suggest you to keep looking for a mistake in your board: pins 8 and 19 on PIC18F2550 are ground pins (zero Ohm resistance between Digital board ground and these pins) and pin 20 is Vdd - you should read +5 between ground and this pin when power is applied to MegaDrum. Check if you inserted PIC18F2550 correctly into a socket, i.e. didn't turn it 180 degrees.

I kept looking for mistakes in the board but didn't find any. Followed your suggestions on what to test too. Here are some pictures of the unit as promised.

Here's the usb board and the cable connected to the digital board. The two capacitors in parallel at the upper right corner replaces the 470n that we couldn't find.


USB board and ICSP cable not connected:


USB board top:


Note that I had to flip this picture horizontally to easily match the board's top picture. Also, we didn't remove the lazer toner from the copper portion to use it as the mask to prevent corrosion.


ICSP cable top (i.e from pin 1 to 5)


ICSP cable bottom (i.e from pin 9 to 6)

[dmitri]

As it happened before with you, just saying you checked everything somehow doesn't persuade me that you did:)
PIC18F2550 should never ever get warm or hot, and especially so since you say it gets hot even without ICSP connected.

Without PIC18F2550 in the socket and disconnected from the Digital Board
1. What are the resistances between pin 4 of the USBExt connector and pins 1,2,3,5,6 of the same connector? Are they all indefinitely high?

Connect the USB and Digital boards together.Without PIC18F2550 in the socket and without applying power (USB is disconnected) confirm the following:
1. Zero resistance between Digital board ground and pins 8 and 19 in the PIC18F2550 socket.
2. Zero resistance between VCC of Digital board and pin 20 in the PIC18F2550 socket.
3. What is the resistance between pins 19 and 20 in the PIC18F2550 socket? Is it more than 1k?
4. What is the resistance between pins 19 and 14 in the PIC18F2550 socket? Is it indefinitely high?

Still without PIC18F2550 in the socket apply power to Digital board.
1. What is the voltage between Digital board ground and pin 19 in the PIC18F2550 socket? Is it 0?
2. What is the voltage between Digital board ground and pin 20 in the PIC18F2550 socket? is it +5?
3. What is the voltage between Digital board ground and pin 14 in the PIC18F2550 socket? is it 0?

Disconnect the power, insert PIC18F2550 into the socket and apply power again.
1. What is the voltage between Digital board ground and pin 19 in the PIC18F2550 socket? Is it 0?
2. What is the voltage between Digital board ground and pin 20 in the PIC18F2550 socket? is it +5?
3. What is the voltage between Digital board ground and pin 14 in the PIC18F2550 socket? is it 3.3? Is it really?

[estregan]

As it happened before with you, just saying you checked everything somehow doesn't persuade me that you did:)
PIC18F2550 should never ever get warm or hot, and especially so since you say it gets hot even without ICSP connected.

Without PIC18F2550 in the socket and disconnected from the Digital Board
1. What are the resistances between pin 4 of the USBExt connector and pins 1,2,3,5,6 of the same connector? Are they all indefinitely high?

Edit: Yes, all are indefinitely high.

Connect the USB and Digital boards together.Without PIC18F2550 in the socket and without applying power (USB is disconnected) confirm the following:
1. Zero resistance between Digital board ground and pins 8 and 19 in the PIC18F2550 socket.

Yes, zero resistance confirmed.

2. Zero resistance between VCC of Digital board and pin 20 in the PIC18F2550 socket.

Yes, zero resistance confirmed.

3. What is the resistance between pins 19 and 20 in the PIC18F2550 socket? Is it more than 1k?

Yes, its more than 1k. When the (+) prod is on pin pin 20 and (-) prod is on pin 19 resistance measured is 4k. When prods are reversed, resistance measured is 10k.

4. What is the resistance between pins 19 and 14 in the PIC18F2550 socket? Is it indefinitely high?

Yes, confirmed that resistance is indefinitely high.

Still without PIC18F2550 in the socket apply power to Digital board.
1. What is the voltage between Digital board ground and pin 19 in the PIC18F2550 socket? Is it 0?

Yes, voltage is 0.

2. What is the voltage between Digital board ground and pin 20 in the PIC18F2550 socket? is it +5?

Yes, voltage is +5

3. What is the voltage between Digital board ground and pin 14 in the PIC18F2550 socket? is it 0?

Yes, voltage is 0.

Disconnect the power, insert PIC18F2550 into the socket and apply power again.
1. What is the voltage between Digital board ground and pin 19 in the PIC18F2550 socket? Is it 0?

Yes, voltage is 0 and the IC gets hot.

2. What is the voltage between Digital board ground and pin 20 in the PIC18F2550 socket? is it +5?

Voltage measured is only +4.2 and the IC gets hot.

3. What is the voltage between Digital board ground and pin 14 in the PIC18F2550 socket? is it 3.3? Is it really?

Voltage measured is only +1 and the IC gets hot.

On the last batch of questions, we disconnected the power when not measuring as the IC gets hot already.

[dmitri]

As it happened before with you, just saying you checked everything somehow doesn't persuade me that you did:)
PIC18F2550 should never ever get warm or hot, and especially so since you say it gets hot even without ICSP connected.

Without PIC18F2550 in the socket and disconnected from the Digital Board
1. What are the resistances between pin 4 of the USBExt connector and pins 1,2,3,5,6 of the same connector? Are they all indefinitely high?

No. Zero resistance is measured between those pins.

In my view it manifests shortcuts between ground and these pins. You should have stopped here.

[estregan]

In my view it manifests shortcuts between ground and these pins. You should have stopped here.

Ooopps! Sorry, I gave you a wrong answer as I misunderstood my partner on this. There are no shortcuts here, resistance is "really" indefinitely high.

[dmitri]

Ok. We will have to be thorough.

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.

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.