(tr)uSDX Forum

A failure on the main board occurred when I was attempting to measure voltages and/or waveforms on the main board header. I was being very careful and used a grounded antistatic mat with a wrist strap… Apparently not careful enough.
Long story short, Vcc now measures zero ohms to ground. Since nearly every active device uses Vcc, finding the cause or causes of the failure will be very difficult. The U2 regulator is OK when I lift L1 off the board.
If anyone has been down this road and can provide insights into what the failure might be, please let me know so I can narrow my search.
73, thanks
John K1JD

Hi John,

Most likely the AtMega got zapped.
Si5351 also fails sometimes

The easiest way to figure it out for sure, is a thermal camera and a Power Supply with current limitation set to max 100mA. Then connect it for max 5 s and see what heats up. This is the bad part to swap.

73 Manuel; DL2MAN

In the absence of a thermal camera, a finger searching for heat is also quite effective.

Ugh, already replaced the Mega once. Thanks info.
73,
John K1JD

hi


my mainboard is also out of working. i made a short between Rf and FWD.
atmega was replaced but when i program the bootloader i see unknowed device.

any suggestion ? 73 Jean-Marie

>>>: avrdude
truSDX-initial_Bootloader(1).hex: 32 366 / 32 768 Bytes (98,77%)
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
>>>: avrdude -c avrisp -p m328p -P COM4 -b 19200 -e -U flash:w:"C:\Users\JM\Documents\Downloads\truSDX-initial_Bootloader(1).hex":a -U lfuse:w:0xFF:m -U hfuse:w:0xD6:m -U efuse:w:0xFD:m

avrdude.exe: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.02s

avrdude.exe: Device signature = 0xffffff (probably .xmega) (retrying)

Reading | ################################################## | 100% 0.02s

avrdude.exe: Device signature = 0xffffff (probably .xmega) (retrying)

Reading | ################################################## | 100% 0.02s

avrdude.exe: Device signature = 0xffffff (probably .xmega)
avrdude.exe: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override
this check.


avrdude.exe done. Thank you.

I use an infrared thermometer gun to check the temperatures of devices in my circuits. It's not as quick or convenient as an IR camera for finding shorts and heat problems, but it works well and provides a precise value for the temperature.