Tube Type Car Radio Repair Tip

Dale, I read that tip about 35 years ago. When i was working full time about 15 years back (And my memory was much better), I had a nightmare radio on the bench that was out of a 1950's car. Ran it for days and worked perfectly. Tubes all tested fine, even with the "tap test'.

 Somehow I remembered that tip and BAM! 3rd tube I tested upside down showed short.
 Replaced tube and radio worked just fine.

Sometimes collecting old radio & TV servicing magazines can save your bacon.
Honestly I don't think I would have thought of turning the tube tester upside down unless I had read & remembered that article. Somehow the weird faults were strange enough I remember them. Probably because I ran into so many odd ball things other shops refused or couldn't fix.

Wow - you could start a Crimestoppers Textbook for antique radio repair with that one. I'll bet a lot of us would not have thought of that trick.

If you have a car radio that mounts in the vehicle with the tubes upside down this can save you mass trouble. 
 me a couple of times.

Radio worked fine on the bench but in the car wouldn't work.

Testing the tubes in the normal fashion shows all the tubes test good.

Now put the tube in the tester and TURN THE TUBE TESTER UPSIDE DOWN, and test the tube.

Yes! I had the short appear ONLY with the tube upside down in the tube tester.

This was a tip from a very old electronics publication. I fought that radio for hours and it worked perfectly on the bench, but the minute it was turned upside down, as it was mounted in the car, it failed.  Fortunately I remembered this tip and I solved my problem. With the tube and tester inverted, the short light came on. Replacing that tube fixed the radio.

A real oddball rare problem, but I did have it happen to me.