HL2 PA issue

[Jim Gonthier]

Hi All, 

Sporadic behavior - Thetis+Hermes TUNE into a dummy load shows 6w. However, hl2setup.exe utility shows PA bias fluctuates in the 1200-1300ma range.

I started to investigate because under normal operation (external amp, making FT8 contacts) everything would be working right, then go to 0w output.

So, do we think I need to replace the two AFT504 transistors, or perhaps try to do a reflow under them?

Appreciate your thoughts,

Thanks, -Jim

KC1WAY

[Steve Haynal]

Hi Jim,

What temperature are you seeing when you tune? Some bias fluctuation is expected. It may be going to 0W because it is overheating.

73,

Steve

kf7o

[Jim Gonthier]

Hi Steve,

I ended up replacing the two AFT504 transistors and now getting a consistent 7w output (as shown in Thetis). The temperature reading goes to -50c (yes negative) during transmission but the rest of the time shows rational readings in the 30 to 40s Celsius. I now suspect my soldering work (soldering iron and hot air) may have damaged the temp sensors, which I learned after the fact is near the AFT504 and I didn't protect with Kapton tape during the soldering session. I've made several FT8 contacts in this current state and getting consistent behavior from Hermes so thinking I leave things as they are for now.

Thanks for you help and 73,

-Jim

KC1WAY