[Boatanchors] NC-240D question

[jeremy-ca]

I decided to start to work today on a recently acquired NC-240D. The first 
thing that I noticed is that the mixer tube was missing a grid cap and it 
turned out that a 6SB7Y was installed.
I removed the bottom cover and after removing the mouse nest over the xfmr 
area and moving the rack over I noticed that the rcvr had been recapped at 
some time in the past. It had the same Sprague caps that National used in 
the Service Dept in the 60's for overhaul of the oldies and the same 
neatness that the Svc Dept was known for.

The 6SB7Y conversion also looked factory neat and you would swear it was 
original. The question is: does anyone know of that conversion and/or know 
if National might have done it? I was in the Svc Dept 1964-67 but dont 
remember anyone mentioning that swap. However lots of strange things went on 
back then, especially with the HRO-50 & 60 so nothing would surprise me.

The 6SB7Y has almost 3X the transconductance of the 6K8 and the late 50's 
sunspot peak probably prompted someone to hop the old girl up on 10M.

Carl
KM1H
National Radio 1963-69