A little known fact is that there is no reliable way to measure the
expected remaining life of a tube. Though we have two vastly different tube
testers, they do not accurately measure the expected remaining lifetime of a
tube. We can measure whether a tube is currently dead or defective. All the
tubes we install in radios which we are repairing or restoring are NOS [new
old stock]. This simply means they may have been manufactured many years
ago, but to our knowledge have never been used.
We test the tubes in each radio, replacing if they seem marginal or
dead. The fact that they tested "good or better" simply means that they are currently
functional. It is not an indicator of remaining life. Tubes generally last
many thousands of hours, and the most common reason for failure of a radio
that comes in to us, is bad Electrolytics, not tubes. Thus-
TUBES -LIMITED WARRANTY
The warranty on tubes is ninety days [90 days]. This applies to all
unit warranties of 90 days, six months or 1 and 3 years. We simply cannot
warrant issues we cannot control.
Radio Repair Guy