PA-30 pilot reported losing radios and the transponder while flying on an IFR clearance.

Narrative:

Picked up aircraft from avionics shop; test flight only one anomaly altitude hold inoperative. They worked on it; I departed and lost the transponder and radios south of hevvn; before the number 2 [radio] failed it defaulted to guard; unable to reach jax on guard I used a relay; told jax I was [diverting] to lal. Through relay I was told to descend to 5;000 ft; then that radio failed; I descended to 5;000 ft; cleared traffic out the window; turned away from the airway then descended and called flight watch on the telephone-asked them to call jax and tell them I was landing at inf; upon landing I immediately called flight watch for the jax number; called jax center on the phone; spoke with the supervisor and let him know I was safely on the ground. Never entered IMC during flight and was approaching WX so the safe decision was to turn around and maintain VFR. Chose not to [divert] to lal as I was a primary target without transponder to avoid adding stress to tampa approach. Called flight watch on the phone to advise of my intentions to avoid concern on the part of jax center etc. I was able to make that call before my anticipated arrival in tampa airspace.

Original NASA ASRS Text

Title: PA-30 pilot reported losing radios and the transponder while flying on an IFR clearance.

Narrative: Picked up aircraft from avionics shop; test flight only one anomaly altitude hold INOP. They worked on it; I departed and lost the transponder and radios south of HEVVN; before the Number 2 [radio] failed it defaulted to guard; unable to reach JAX on guard I used a relay; told JAX I was [diverting] to LAL. Through relay I was told to descend to 5;000 ft; then that radio failed; I descended to 5;000 ft; cleared traffic out the window; turned away from the airway then descended and called flight watch on the telephone-asked them to call JAX and tell them I was landing at INF; upon landing I immediately called flight watch for the JAX number; called JAX center on the phone; spoke with the supervisor and let him know I was safely on the ground. Never entered IMC during flight and was approaching WX so the safe decision was to turn around and maintain VFR. Chose not to [divert] to LAL as I was a primary target without transponder to avoid adding stress to Tampa approach. Called flight watch on the phone to advise of my intentions to avoid concern on the part of JAX Center etc. I was able to make that call before my anticipated arrival in Tampa airspace.

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.

Attributes
ACN	1522386
Time
Date	201802
Local Time Of Day	1201-1800
Place
Locale Reference	ZJX.ARTCC
State Reference	FL
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	PA-30 Twin Comanche
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Airway V97
Flight Plan	IFR
Person 1
Function	Single Pilot
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 35 Flight Crew Total 9000 Flight Crew Type 170
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Clearance