One thing I can tell you about that rig was that Tom Knoll kr8c inherited the radio a heath sb102 from his sister in law who was killed while crossing a street in Michigan and Tom told me that he hasn't had to replace a tube in that rig for over 25 years.  He still compliments me on that alignment job I did on that rig even though it was 30 years ago. 73- pat kk3f