Hi Wayne,
To answer question 3… there is a better transistor for replacing the BS170’s - TN0606. The data sheet can be found here:
Note that the source and drain pins are reversed from the BS170 so you’d flip the TN0606 upside down (flat side against the washer). Others have made this substitution with excellent results. Again, it’s a good idea to place a very thin layer of thermal grease on both sides of the transistors to maximize heat transfer to the board.
Hope this helps!
Tony - AC9QY
Hey, all. First--I have been having a great time with my QDX. I've made numerous FT8 and JS8 contacts. I've even worked with other FSK modes with this little transmitter. I built mine for 9VDC input and I am seeing 5W on 80, 40, and 30 meters. I sometimes see between 5.3 and 5.6 on 40M. I am getting 3.8W on 20 meters.
So, Right when I was working an FT8 QSO, I heard what sounded like a crack sound from inside the QDX enclosure. Then, the smell. I knew then something went terribly wrong. I found the cracked BS170 as soon as I pulled the board out of the enclosure. I'm in the process of buying new BS170s. I know it is a TO-92 style, but I am seeing other variants of the transistor: D26Z, D74Z, etc. I have three questions:
1) Is there a specific BS170 I should get or will any of them work provided it's a TO-92?
2) Is there anything else I should do to prevent another BS170 fail?
3) Has anyone found an alternative to the BS170 that has less potential for failure?
Thanks,
Wayne KB4DSF
