> for "cost savings" ?
Perhaps. It may really be better.
Look at a miniature tube (12AX7). Fairly fat leads come through a thick glass bottom button.
Bust-open the base of a dud conventional Octal tube. The leads are very thin, long, and must be threaded to and soldered into pins on a separate glued-on base.
The reason is that it is hard to get a long-lasting vacuum seal metal-to-glass, especially over a wide range of temperatures. Glass and metal expand at different rates, and the seal wants to crack. Historically, smaller leads reduce the problem. However small leads are near useless for carrying heat out of the electrodes. For several reasons, larger leads became practical as the Miniature tubes were developed. This allows a short fat connection. It also allows the lead to be the pin, saving threading and added parts. The instigation may have been low loss at very high (radio) frequency. But a fair amount of heat can be carried out the same way. And once debugged it was somewhat cheaper.
Conventional Octals were in decline. After the first decade of Tube TV, the Octal-size jobs went to large tubes on Miniature-type bases (but larger), like we find in a few Bogens. Since the old Octal designs and machines were working well, the few Octals still in production stuck with the old ways.
But by the 1970s the Octal machines may have been getting tired, or being sold-off to Hungary and other odd corners. And the total tube production in each hanging-on factory may not have justified *two* base systems with different machines and different materials to stock.
I think the coin-cell Octal is a giant Miniature, plus an adapter to fit Octal sockets. Note the stiff leads come out in the right places. No threading thin leads into the right pins, it just drops in.
The threading of Octal leads to pins may parallel the early IC chip process, where the pads on the dies had to be stitched to the pins on the package by hand. Once the die production got good, hand-stitching the die leads became a major cost and unreliability problem for the industry. One approach was leg-less packages, where the die pads were grown larger and soldered direct to PCB (an early SMD). This that and another, the cost of terminating an IC die dropped from several dollars to several cents over a few years. The tube makers may have heard of this and decided to re-study their techniques. Miniature was hard to improve (reduced cost had been part of the project) but Octals begged for re-thinking with now-mature technology.
OTOH, we all hated coin-base (perhaps irrationally) and tube makers learned that their few remaining markets would pay the prices for a "real" (old style) base. So coin-base may be a good idea that we rejected.
Topic: What tube is this (Read 5412 times)