FZ-1A transistors again

[SonicVI]

Do AC107 or 2N404's have proper specs to be used in an FZ-1A clone (after being tested for gain and leakage) ?

[petemoore]

Schematic, or at least what Q's it calls for, then The type and G/L #'s of your Q's.

[brett]

I'm no expert, and I'm relying on memory, but here goes anyway....
I'm thinking of Q1 here.  The FZ1A uses an old-fashioned method of biasing that relies on leakage.  You'll notice that there's no V+ to base resistor to supply the base current and voltage.  AFAIK this will probably mean that only a small range of devices will work.  First, no Si devices will work coz they're too low leakage.  It's designed for Ge device leakage.  Second, the leakage can't bee too high or too low.  I *think* I can hear some mis-bias (like having a noise gate turned up too far) in the riff of the Stone's "Satisfaction".  So maybe the transistor was a little under-leaky (??) and the voltage on the base might have been a bit too low (??).  Anyway, that's wild speculation.  (Though someone with the CD could look at the waveform and see if it's very asymetric).

I can't remember what the setup is for Q2.  If the base looks like it needs voltage/current from the collector it too will have to be a leaky device.

I hope that helps somewhat.

As pete said, *please* include a link to a schematic with questions such as this. It makes it much easier to give good answers and saves the answerer time, so it's a win-win.

cheers

[petemoore]

Interesting about Q1 which looks like a 'common' emitter stage with a bit larger resistor.
 Gueseppe wonders what it is about Q1 in FZ1A that Requimends a 'leaker'...only thing I 'see' that stands out Is the 10k...well the 20uf staging cap, but that wouldn't influence bias ..er...

[gez]

Getting the bias right seems to me more critical than the numbers on the can.  Get whatever Ge trannies you can and test them in an actual circuit.  Decide for yourself.  What you don't use can be used in other circuits.

Have you checked my notes on bias (I did quite extensive testing on all this)?  Use the search function and you'll find them in a number of threads.