Melcor 1731 Teardown

[TheseGoToEleven]

hfe depends on current level used, what was the current used for getting hfe = 75?

That is a good question. On all the transistors, I desoldered them from the board and popped them into a cheap tester, which I think runs a couple of different tests and reports the highest value of hFE it finds. At this point there are so many loose parts that it's probably easier to find the bad part by breadboarding the whole thing.

 

[Whoops]

edit: also regarding OSA, there were a looot of variants out there of their preamps. I've never seen one with a Melcor 1731 though.

the old OSA website it's still accessible in Way back machine:

https://web.archive.org/web/20070622114131/http://www.oldschoolaudio.com/products.html

 

[z11111]

the old OSA website it's still accessible in Way back machine:

https://web.archive.org/web/20070622114131/http://www.oldschoolaudio.com/products.html

thanks for the heads up, turns out ours is the "MP1-L3 a.k.a. "The Big Daddy"" lol. I've seen even weirder OSA stuff that never got released, as well.