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Fried my board?

Question asked by Greg73 on Dec 1, 2011
Latest reply on Feb 22, 2013 by Clive One

I hooked up an 2x16 LCD display with backlight to the board's EXT_3V pin and GND. (The display is a 3V type: both logic and backlight, so not the typical 5V one). I didn't experience any trouble, the USB didn't disconnect indicating high current etc. The display had lit up and one line of blocks showed up - that's the expected behaviour. A few minutes later I disconnected the board from my laptop.

An hour had gone with coding and I wanted to download my code so connected it. It gave me an error message box:

Fatal error: ST-Link, No MCU Device found.
Session aborted!

After pressing OK another message box appeared indicating that the flash loader was failed.

I dis/reconnected the board, restarted IAR, restarted Windows with of no avail. The strange thing that the MCU is seems to be working - my last code is running, flashing the LEDs in every 5s as I was experimenting with RTC alarm interrupt.

I checked the voltages and they are correct. Checked the U1 LDO and it has the correct output voltage of 3.3V which is forwarded by D1 Schottky with the loss of ~0.3V - OK. The red LED is lit, the dual colour LED is also working, it is red. The jumpers are OK too.

Measured the MCO output with freq counter at SB17 and had 8 MHz readout.

No idea. Is it the  U2 (STM32F103C8T6) which is corrupted? I can't imagine how since it has a normal 8MHz output clock. Or the main MCU? It seems to be up and running with a fairly complex code.

I just ordered a new one anyway, but would like to know if it can be repaired so I'd thank any idea...