I first draw out the map of all the tubes, place the correct tube designator and Tube number. This ensures i have the correct tube placement and that as I test i can mark off “bad” or “good” or “weak”. The weak might be good enough to get the amplifier working, but will need replacement for long term use.
Next I select a tube and and gently remove the glass electron masterpiece.
As you can see, some tubes are in great shape and others need some cleaning to be able to read the tube part number.
I have several resources to verify that the tube I have can be tested in the Knight Kit Tube tester that I have had for over 20 years.
If the tube is old enough I can use the scroll paper inside the KNIGHT “KG” 600 “B” (Why they had the letters KGB in the nomenclature of the tester I have no idea!) Kit test kit with the back lit scroll.
If not I have to turn to my other resource book with newer tubes. As the case for this very cool 6AL7 radio tuning tube. The tube lights the upper part of the glass on a grid that allows the user to “see” how in tune the radio station is getting. (I was very impressed as i have never see a working signal strength tube in working condition, and was surprised about how bright it really was.)
It was go time… setting the correct switches, turning to the correct voltage and socket selector I was ready to test!
After a test of all tubes my failed list will be easy to acquire from E-Bay as I have already started the bidding process!
Here are tubes I need to replace out of 14 tubes: