Narrative:

IFR clearance was received in the air from center. Initial clearance was as filed with a climb to 9;000 feet. (That climb was revised to 7;000 feet by approach due to traffic.) shortly after a handoff to approach and while climbing through 5;000 feet; both navigation/communication radios (garmin 530W/430W) displayed a message indicator simultaneously. At the same time; a subtle static noise came through the headset. Within seconds of the message/static; smoke appeared in the cockpit along with a strong smell of an electrical fire or short circuit. I declared an emergency with ATC; switched off the autopilot and made a turn to the north while beginning a rapid descent. Based on my position; I knew there were two airports and flat terrain to the north/northeast. ATC gave me vectors to the nearest. After stabilizing the descent; I used the 'nearest' function on the garmin 530W and chose ZZZ. That airport was 3-5 miles further than the nearest; but I was more familiar with the airport and the surrounding area. It also had a longer runway for a downwind landing and terrain short was suitable for an off-field landing. The electrical smell and smoke cleared in about 30-60 seconds after it appeared. I leveled off around 800 feet AGL. At around 7 miles; the airport came into view. I performed a downwind landing to the north. Touchdown and rollout were normal. I contacted approach clear of the runway and notified them that I had landed without incident. Post flight inspection revealed the garmin gtx 330 transponder had failed internally with indications of heat visible on the main circuit board. At least two areas showed charring/melted solder. The fuse on the main fuse panel did not trip. Garmin gtx 330 was installed in february 2013 and had around 250 hours of flight time in service since new. Unit has been returned to garmin for warranty service.

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Original NASA ASRS Text

Title: PA32 pilot on an IFR flight plan experiences smoke in the cockpit and diverts to a suitable airport with the aid of ATC. Post flight inspection revealed that the transponder had failed internally.

Narrative: IFR clearance was received in the air from Center. Initial clearance was as filed with a climb to 9;000 feet. (That climb was revised to 7;000 feet by Approach due to traffic.) Shortly after a handoff to Approach and while climbing through 5;000 feet; both NAV/COM radios (Garmin 530W/430W) displayed a message indicator simultaneously. At the same time; a subtle static noise came through the headset. Within seconds of the message/static; smoke appeared in the cockpit along with a strong smell of an electrical fire or short circuit. I declared an emergency with ATC; switched off the autopilot and made a turn to the north while beginning a rapid descent. Based on my position; I knew there were two airports and flat terrain to the north/northeast. ATC gave me vectors to the nearest. After stabilizing the descent; I used the 'nearest' function on the Garmin 530W and chose ZZZ. That airport was 3-5 miles further than the nearest; but I was more familiar with the airport and the surrounding area. It also had a longer runway for a downwind landing and terrain short was suitable for an off-field landing. The electrical smell and smoke cleared in about 30-60 seconds after it appeared. I leveled off around 800 feet AGL. At around 7 miles; the airport came into view. I performed a downwind landing to the north. Touchdown and rollout were normal. I contacted Approach clear of the runway and notified them that I had landed without incident. Post flight inspection revealed the Garmin GTX 330 transponder had failed internally with indications of heat visible on the main circuit board. At least two areas showed charring/melted solder. The fuse on the main fuse panel did NOT trip. Garmin GTX 330 was installed in February 2013 and had around 250 hours of flight time in service since new. Unit has been returned to Garmin for warranty service.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.