[Boatanchors] Tube Testers

[Larry Kirkland]

I recently had a friend give me a Swan 500C in really great cosmetic 
condition.  It received well, but the power output was only barely 
measurable on the wattmeter.  My first suspicion was weak tubes.  All 
checked OK on my military TV-7D, but I could not check the final output 
tubes (6LQ6/6JE6) on the TV-7 because of the oddball compactron base on 
these tubes.  I remembered that I had a B&K portable tester that would 
test them, so I used it and they tested "very good".

One of the radio's main symptoms was very low idling current on the 
output tubes.  Even turning the bias pot all the way down only showed 5 
ma. of idling current.  Plate voltage was good, and the screen voltage 
was to specs.  The cathode resistors were "on-the-money" and the 
metering circuit was without fault.

I scratched my head for several days on this one.  Then looking through 
my tube stock, I found a "very used" 6LQ6 and substituted it for one of 
the final tubes, and guess what?  The idling current had increased to 40 ma.

So I guess my question to this group is:  What kind of tube tester is it 
that shows a tube as "very good" when it obviously has almost zero emission?

Moral to story:  Take tube tester readings with a big grain of salt!

If anyone has any 6LQ6/6JE6's for sale or swap, please let me know.

73's
Larry W4LK