[Rod]

I think I have blown one or more transistors on my circuit board. Last night I left my scope unattended while in tracking mode. While I was away the laptop shut down while the board was on. Unfortunately I can no longer slew in altitude and the motor just makes a faint buzz sound in tracking mode. I replaced the hex inverters but still have the same problem. I tried another computer and had the same problem so it is not the parallel port.

I am thinking I should replace one or more of the darlington transistors on the altitude side. I am using TIP102s but I have 4 TIP122s which I believe can be used instead. Should I just replace all 4 on the altitude side or is there a simple way to identify which of the transistors is damaged? I have a cheapo multimeter but I am pretty ignorant when it comes to electronics - can do basic soldering though.

Thanks,

Rod.