27 Oct
2025
27 Oct
'25
9:22 p.m.
On ETSY there were 24 pieces of the MPS3639 for a very reasonable price.
They sold a few hours ago, so Christian may have found what he was looking
for.
On Mon, Oct 27, 2025 at 6:33 PM Christian Corti via cctalk <
cctalk(a)classiccmp.org> wrote:
It seems that nowadays you can't get *any*
replacement for failing DEC
3639 aka 2N3639 transistors. All parts are obsolete and unobtanium, e.g.
2N3640, PN3640, MMBT3640 and so on.
So, what can be used instead? The most important electrical parameter is
the storage time. It needs to be *very* low, around 20-30 ns.
Does it mean that a failing PDP-8 will stay a dead PDP-8 from now on?
Christian