In Reply to: Replacment chip posted by R. Moore on 08/07/01 at 11:37 AM:
The 2N4900 and the 2N1671B may have some sources of supply. Try looking at:
For the other two devices though, I couldn't find any references at all. Given that the 2N1671B is a unijunction transistor, the spot welder must be thirty some-odd years old. As time goes on, availabilities of the parts with which it was designed will very likely diminish.
If the spot welder is just one piece and you really want to keep in in service, and if you know the existing circuitry and its design intents, you might consider redesigning the circuit board with more up to date components. Failing that, it may be time to shop for its replacement.
In any event, good luck.
John Dunn - President