Hi manekinen,
I built this to repair one Atmega328 that got wrong fuses because of some usbasp complications.
I built it and it worked the first time, so I was able to repair my 328p successfully. Thanks for that.
Some strange problems happened afterwards:
1. I put a atmega8 that was good, but just for a test. Let GREEN was blinking. Looking over serial connection, I saw the following: http://i45.tinypic.com/2hqrvr4.png
The chip became unreadable and it was working before via ISP, etc. Unable to fix it I tried to raise the voltage, from 12V to 18V, but that broke the chip permanently: the RED led turned on instead of the blinking green.
2. I tried with a working atmega168. It worked well – settings set back to default . Nice constant green led light.
3. I tried with another 328p . Worked good.
4. I tried with an Attiny2313 . It worked, but the Serial debugger showed some weird data:
http://i47.tinypic.com/iwq5hc.png
But this worked too.
5. I tried a brand new atmega8 . The green light was blinking. I then connected it via ISP and was able to use it correctly. Putting it back to Fusedoctor, showed blinking green light again. Why?
I connected the serial debugger. It showed everything was normal: http://i47.tinypic.com/15ezujs.png
I disconnected the serial/uart debugger, pressed the START button, but the green light was blinking again
6. Inspecting the PCB, I found an improper soldering at one of the 1K resistors. The circuit was interrupted there. Strange that atmega168 , attiny2313 and the atmega328p (the reason I built your tool) where all working. So I soldered the resistor correctly, BUT:
NOW NONE OF THE LEDS TURN ON. The debugger now only shows:
http://i48.tinypic.com/3466elu.png
And stops there . No leds turn on regardless of what I put in the sockets.
I hope this wasn’t a total waste of time, and there is something I can do to make it work as expected. What could be the cause of all this?
My only change to your original schematic was using 2x BC327 instead of BC557. Any help would be appreciated.