Quote Originally Posted by jimkarl View Post
Don't have any of those but can order them. I have BC549B's and BC547's.
Can't find hardly any info on a TZ81. Only thing I saw on a data sheet was hfe value of 60. Google search on alternatives yields only 2 or 3 mentions of alternatives. One said 2n9249 was the alternative but now defunct. Another said people have used 2n3904 with success. Those seem to be readily available too. Thoughts on that vs the BC550c (or my 549 or 547) given the limited info on the TZ81 spec? I confess I'm a novice with respect to understanding transistor specs (and a lot of other electronic related things too lol but i like to learn.)
Pretty much any NPN transistor should work. The BC550C is a low noise very high gain device. The BC549B is of the same family and should work great. Any similar spec USA part should work just the same as well.