Fan & Servo Questions for New Build with RD3


 
Good progress... The ATMega is functioning fine as you can see...
So yes, it sounds like a reasonable assumption that the BS170 could be bad, or the large MOSFET could be bad, or there could still be a short somewhere...
Since you've narrowed it down perhaps it is time to pull the BS170 from the board, then reinstall Pin5 on the ATMega and at that point your blower should be off... If it is not off then the large MOSFET is toast or you've got a short somewhere.
 
Pulled the BS170, reinstalled the ATMega with all pins firmly seated and the blower is now off.

Time to order a new BS170, right?!
 
Yes, that seems like the proper coarse of action, unless you are impatient...
There is a BS170 that is used to drive the buzzer, Q2, it's right there next to the buzzer. You could pull that BS170 and use it in the blower circuit. (of coarse the buzzer will not work but everything else will) There's also a BS170 used to control the backlight of the LCD (Q4), you could use that one too, but the backlight is a more useful than the buzzer IMHO. Though you could just ground Pin 16 on the LCD and the backlight would come on at full brightness (but not respond to the HM backlight level setting). I would go for the buzzer transistor myself.
 
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I just placed an order for a handful from Mouser. I wouldn't call myself uber patient, but I would rather wait a few days and put in a new one instead of trying to remove the buzzer transistor. I didn't get the blower transistor off 100% clean. Part of the pin to ground broke off in the hole. I need to plan for the worst at this point knowing how I've manhandled this thing throughout.

Thanks again for guiding me each step of the way here Ralph!
 
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