Yesterday a friend came over with a freshly assembled MSI using the Ver. 3 board so we could test/stimulate it and load the newest firmware.

A few components were in backwards which I corrected, and the soldering job is not the best but the joints were good.

Unfortunately we could not get the board to boot. Upon power up, none of the LEDs blinked and Megatune would not communicate. Attempting to load firmware using the boot jumper also failed.

We began to troubleshoot the circuit starting with the 5V supply, which seemed fine. We then scoped the microprocessor clock to make sure there was a signal. Again, seemed fine. Things got weird when we checked the 5V supply rail with the scope.

On the 5V rail, almost everywhere in the circuit, was a squarewave at the same frequency of the microprocessor's oscillator. This was detectable at all the processor supply pins, the 5V regulator, filter capacitors, proto board, etc.

I've checked that all filters are installed in the proper polarity and that there are no solder bridges in the oscillator circuit. Things are complicated somewhat because the processor is soldered directly to the board.

Checking the schematic shows there should be no obvious interference path between the two and certainly the processor will never boot with that much noise on the board.

Thoughts? Anyone seen this before?

 

I've never seen this before. IF he soldered the CPU directly to the board, he may have fried something... I'd start by desoldering the CPU, and then scoping all the same traces again to see if that square-wave is still showing up.

Ken

 

That's what I'm thinking. The CPU pins were actually soldered very well, much better then the rest of the board. But of course that still doesn't mean that it was not overheated or zapped...

We began to unsolder the CPU but ran out of time before it could be removed from the board.

After weighing his options, I believe that he's just going to cut his losses and get another kit or one fully assembled. The amount of time and effort required to swap the non-socketed CPU makes starting from scratch an attractive option.

 

Heh, I have a nice desoldering tool, so I forget what a pain desoldering components can be with a solder wick for example.

Before I had a desoldering gun, sometimes I'd use one of those cans of air, and put on some safety glasses, and blow the solder away after heating it with an iron. That worked, but wasn't all that safe (hence the safety glasses).

Ken

 

Back in the day, I actually had a very good desoldering station. Then the element burned out and I didn't bother fixing the thing. Right now all I have is a vacuum solder sucker, made in China. Works well, but not for delicate stuff.

FYI, be careful when using the term "solder wick". The company that owns the trademark is insane about protecting it. I used that term in my desoldering page on my website and was served with a notice from their lawyer! Seriously.