Did many silicon transistors ever come in T05 packages?

[Nitefly182]

I opened up a rather obscure pedal today and saw a pair of unmarked T05 transistors on the board and was a little surprised because the builder doesn't seem like the type that would use a part with potential temperature instability or inconsistency of parts normally associated with germanium. I haven't seen any T05 silicons though so Im wondering what the deal is. Anyone know?

[John Lyons]

I have a several big metal can silicon devices that I thought were germanium at first.
When they came to me I assumed they were mislabeled as silicon but they had no
temperature fluctuation when I tested them so they must be silicon...

Not sure how common they are/were...

[Cliff Schecht]

I've got quite a few silicon large-can trannies (don't take that out of context) that I initially thought were germanium. If there is any particular one you're looking for, I have access to quite a few NOS 2NXXX and 2NXXXX series transistors .

[R.G.]

The TO5 case was the standard for silicon, just like it was for germanium, for most of the 1960s. In terms of raw quantities, there were many more silicon transistors in metal TO5 packages than germanium, because germanium use tapered off very quickly once silicon's production problems started getting solved - it was just a superior material for electronics in most ways. The sheer number of transistors made back then (about 1960-1970) was much smaller, as there were fewer electronic applications and transistors were *expensive*. In the beginning, only computer companies and the military could afford them. Later as Fairchild invented the "planar process" of cooking a whole batch of them at once on one 2in/50mm diameter wafer, production cost per transistor came down and the per-transistor price got better as the assembly process was automated.

Steel packages were used to hermetically seal the transistor die into the case. Before glass passivation was invented, contamination on the outside of the transistor die inside the package could ruin a transistor quickly. Hermetic sealing was the military answer, as it had bee for certain components in the tube era. When glass passivation was invented, there came some freedom to lighten up on the packaging, so the much-cheaper epoxy encapsulation packages were invented. They were universally thought to be cheap and shoddy contrivances in the engineering environment in which I stared work, but later became accepted when they (im)proved their reliability. As it always will, economics won out and the TO5 went the way of the dodo in the early 70s except for exact-replacement military work.

So yes, there are a LOT of silicon TO5s out there.

[cathexis]

2N3019



2N2218A

Both silicon, both great in the Axis Fuzz, especially the 2N2218A. Real low gain, like 60-120 maybe...

LARS

[Nitefly182]

OK so its a lot more than I thought. I was just surprised to see them in what I had originally thought was a primarily op-amp design. Thanks guys!