After 2 years of perfect operation, my SunSDR2-Pro developed a PA failure. No output power on HF but VHF is fine. I have confirmed that all ExpertSDR2 settings are correct, and tried other ANT ports, etc.

Lacking schematics, does anyone know if there is U.S. based repair service?

Paul, W9AC

I decided to diagnose the failure on my own. Both Mitsubishi RD16HHF1 PA transistors show a hard gate-to-source short. I ordered several from RF Parts in California (USD $4.25 ea.) and got extras as back-ups. Access to the transistors is very easy. The only caveat is that the source lead is heat-sinked and requires extra heat to remove.

If anyone attempts this repair on their own, be careful to: (1) apply only enough heat to remove solder; and (2) only bend leads when solder is completely molten. Otherwise, you risk lifting the delicate PC board trace. I would not attempt to cut the transistor leads in this case. The cutting shock will also lift the PC board trace. If that happens, you will be extremely unhappy.

I will report back after the transistors arrive and are installed in my SunSDR2-Pro. Hopefully, the driver transistors have not also failed.

Paul, W9AC

Hi Paul,
www.nsiradio.com is authorized service center for Expert Electronics products in USA. After replacement of transistors bias adjustment is needed. We can help you over TeamViewer. Please create a support ticket online, will schedule convenient time and date.
73,
Yuri N3QQ

Thanks, Yuri. I'll contact you after the repair is complete.

Paul, W9AC

I completed the PA repair in about ten minutes. HF PA power is about 22W with a supply voltage of +15.3V. Installation of the new Mitsubishi RD16HHF1 MOSFETs was easy. A small dab of silicone thermal grease is applied to the back side of the MOSFETs and then they're screwed down to the heatsink. An insulated shoulder collar is not needed.

Now on to bias adjustment. Presently, Rx current is 1.10 Amp. Tx idle current is 1.54 Amp after the repair.

Paul, W9AC