[R-390] OT: Leakage testing a 1L6

[Barry Hauser]

N4BUQ wrote:
> I know some heaters are known to sag when hot and touch other electrodes
but
> I figured in a 1.4 volt tube, this wasn't very likely.  Is the leakage
> something other than one electrode touching another?

I don't know about the low filament voltage vs. "sagging", but the 1L6 is
one of those tubes you are NOT supposed to tap during the shorts test.
Never could fathom that fully, as these are mostly all used in portable
equipment.  But if it is already questionable -- a light tap or two might be
in order.  (If you had Nolan's trick hammer -- you could probably fix the
thing.)

> By the way, one of the symptoms the radio displays is that it works
(rather
> weakly) for about 30 to 45 seconds and slowly fades into nothingness.  I
> sort of assume this is heat-related and the leakage is "building up" after
> warmup, but I'm just guessing here.

Sounds like it.  I wonder what would happen if you ran the T/O on its side.
Sounds dumb, but ... well, yeah, probably is a dumb idea.

As I recall, you have an H-500.  Could be worse.  If it were a 600-series,
you'd also have a  ballast tube (50A1) to worry about.

Incidentally, it's a better value to buy another TO that's a tad shabby but
works.  Pay about $50-60 and get a good used 1L6 with radio included for
another $20.

Trouble with that plan is then you need another 1L6 for THAT radio.

You might want to consider getting a 1LA6 loctal tube and making up an
adapter out of a loctal socket and 7-pin tube base or plug.  (pretty much
pin for pin except the one extra.)  The word is that they are electronically
identical, though the extra lead length involved in the adapter may
complicate alignment a bit.

Someone has also designed a solid state replacement for the 1L6.  Circuit
and photos are on a website which you can find with a search pretty easily.

Barry