[Hallicrafters] SX-25 and Substitute for 6F6-G

[Al Parker]

Hi Jon,
    Substitution charts vary, some will only recommend direct subs only if
all parameters are the same, or at least if the specs of the original one
are less than the sub (e.g. plate or screen max. voltage).  For our
applications, the first thing to look at is pin compatibility.  I've got one
book that says the pinout of the 6F6 & 6V6 is different, but it isn't, for
our general purposes, if you look at it.
    1 of my bks says that the following may be subbed for a 6F6:   6DG6,
6K6, 6L6, 6U6, 6V6, 1611, 1621, 1622, 5881, EM84, EM840, KT63.   It won't
necessarily work in all cases, and particularly in the opposite direction,
but you're not likely to damage the circuit, and if only briefly, not the
tube.  You'd soon have problems in many applications if you sub a 6V6 for a
6L6.
    This is a generality, as many things can enter into particular tube
circuit design & tube selection.  That's why we have so many different nrs,
& many are substitutable.  But, go ahead and put in a pair of 6V6's in the
place of your 6F6's, and you're not likely to notice any difference, nor
will the radio.  I ckd the tube ratings, the 6V6 has higher plate & screen
voltage than the 6F6, it can supply more output power, and has lower
filament current.  (If you don't have a tube manual, you oughta find one).
(to paraphrase warranty statements, "your observed results may vary")
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info


----- Original Message -----
> I have a questions in regard to a viable substitute for a 6f6-G in a sx25.
I was told that as long as
> I replace both tubes in the audio output stage I could use a type 6V6.
This
> pleased me since I have several of those but no spare 6f6.  I looked at an
> online tube database but it listed no such substitution.  In fact, it
listed
> that there was no substitution at all for a 6f6-g.  So, do I go with the
6v6
> substitution, a different type, or just save the headache and buy a 6f6-g?