[Hallicrafters] Bumblee Caps.

[Ross Stenberg]

Yes but do they have the effervescence, sonic purity, musicality, and 
clarity of those old caps :^)

 >>>They were indeed made by Sprague. Check old catalogues. Sprague made 
both Black Beauty and Telecaps. They look the same. The BB's have the 
code stripes on them which was an industry standard at the time. BB's 
were oil-filled and that was part of the problem. The filling was done 
by means of a tube also used to hold the lead on one side. The solder 
for the lead sealed the tube. If too much heat was applied when 
installing the cap the solder melted enough to cause a slow leak. There 
may have been other problems: all the BB's I've dissected had distorted 
windings. Perhaps done to adjust them but I think more likely 
unintended. Not all molded body caps of the period were bad and Sprague 
also made a similar cap in a dipped resin case and these seem not to 
have had an unusually high failure rate. The winding was plastic 
impregnated paper and should have lasted longer than the plain paper 
dielectric in the wax paper type caps. Life limitation due to 
degradation of the paper was well known at the time and all 
manufacturers of paper caps supplied derating charts showing life 
expectancy as a function of applied voltage. The higher the ratio of 
rated to applied voltage the longer the expected life was. Oil filling 
was supposed to reduce this effect. I think Sprague made some blunder in 
their manufacturing procedure. BB caps are found in some very high 
quality equipment and are not always bad but usually are and are worth 
replacing on sight. Beside, modern film caps have much better 
characteristics than these old caps did when they were new.