Mdcalvert wrote:

My Westinghouse Model WR-272 (circa 1937) requires an "orignal" design 6U5 tube
for the Tuning Indicator. The "original" design featured a glass bulb that was
shorter than the dimensions listed for the 6U5 in all of the online tube
manuals (RCA and Sylvania from 1943 on). In fact, the radio chassis is
designed so that the tube's maximum seated length (measured from bottom of base
to top of glass tube) can be no longer than 3 inches. The tube socket is loose
and connects to the tube base and the tube and socket can be adjusted back and
forth, in and out, from the hole in the backside of the tuning face of the
radio. Interestingly, the adjustment appears to accommodate tubes that are as
short as two inches.

Hi.
You might want to try this question on rec.antiques.radio+phono. I
personally haven't ever seen a short 6U5 and I'm struggling to visualize
your situation. Nearly always they are simply clamped into place and
the clamp could fall on the glass envelope as easily as the base...with
some buffer material between the tube and clamp, of course.
There are also the ST 'bottle' shaped tubes that sometimes won't fit but
the more common version is the straight sided tube that has the same
diameter from top to bottom.

HTH,

Bill