error on small bear Fuzz Face transistor tester?

[dai h.]

http://www.smallbearelec.com/HowTos/...eFAQ/FFFAQ.htm

by any chance, should C be E be reversed in this diagram?



If I reverse C and E and hook up everything as shown (with a PNP Ge transistor), I get a picoamp current reading on my DVM on the 200uA setting. (At the moment a 2SB187 that has settled at about 9.7uA which goes up if hold it between my fingers which sounds like the hypersensitivy to temp. described in articles.) If I hook up as shown in the diagram, the current reading shoots up.

Thanks!

[dai h.]

well, I guess the diagram is right and I have a bunch of leaky Germaniums... lol. Even ones out of the package (NOS condition) have greater than 300uA of leakage. And the leakage seems to directly correspond to the amount of gain (i.e. the more the leakage measured, the greater the gain).

[Enzo]

Seems to me in my aging recollection that Ge xstrs tend to be leaky in the first place.

[dai h.]

right, I was hoping for good results since some people reported good results with Japanese Germaniums. Anyway, I did finally manage to find one under 300uA of leakage for the higher gain one (228uA) and some more for the lower gain one plus even more lower gain and lower leakge ones which I are apparently useful for a Tone Bender copy. So I stuck one measuring about 84 for the 1st one, and 135 for the second one (an NEC 2SB163 and Matsushita 2SB176 respectively) in my Roger Mayer Classic Fuzz (variant of a Fuzz Face with slightly different values) and it sounds pretty good (doesn't clean up too well but *I think* that is from the difference in circuit values). This below, but the output volume pot is 47k log, tone 2k2 lin. and the 33k is a 47k trimmer (which I adjusted to 33k).



Just measured the originals ("AC128" E.Euro??), and the 1st one seems to have massive leakage and gain (around 1.5mA leakage, 3.5mA collector current so about a gain of 200--the reading doesn't stay very stable). The 2nd one had 453uA leakage, 1.427mA collector current, so gain about 108. With the originals, the fuzz never really worked that well or sounded particularly great (apparently other RM Classic Fuzzes which I gather are older production can contain other transistors and can sound good however, reportedly).