That's it, the thing doesn't fire up as it should, and the bridge rectifier/voltage regulator and some IC get really hot.
It seems to be a short of some kind, as it is drawing a lot of current from the power supply.
I checked the voltage regulator output, it measures 2.2ohm :o between it and GND, but I haven't been able to track the cause of the short.
The strange thing is it worked ok last time I used it, then I go on vacation, and when I return, bang! it doesn't work anymore!
Could it be some SMD component (capacitor?) failing suddently, or may be a chip failing because of static discharge or something like that? I'm stuck.
I checked all those little smds things that I suspect are decoupling capacitors (they go between vreg and gnd) but none of them where the cause.
I think I'm gonna need to buy another programmer :icon_evil:
Regards!
That is strange. The STK500 is considered a fairly durable programmer that being said it is an exposed board so it is possible something happened. I believe there is a schematic for it published somewhere.
Do some poking around, searching first of course, at AVR Freaks to see what you can find.
Andrew
I have no idea what an STK500 is, but...I've fixed many things with the same problem.
Power it up and feel if any other devices are getting hot.
If you can, try and isolate the power supply from the circuit and see if it's functioning.
You may be able to see if something is burnt, or be able to check for a shorted component along the supply rail.
A really fun way to find a bad/shorted component is to use an external power supply instead of the internal one and feed it a ton of current until the bad part blows up!
There's a lot of info in AVRFreaks Forum, including the scheme for the STK500!
Sadly the component that was in short was the main MCU... so I'll have to buy another programmer :icon_rolleyes:. I could try to replace it (there are instructions at AVRFreaks) but I don't have any kind of tools to work on SMD at that level of complexity.
But what on Earth can cause this kind of failure? The last time I used it it was working fine, and 20 days later bum! it's dead.
Thanks guys
Miguel
Since I've probably replaced hundreds of SMD microcontollers and microprocessors I can only say S*&T happens.
sometimes a bad or failing buffer or something attatched to the MCU will take it out.