[sdiy] Newbie & Zener D equivalents

[Scott Bernardi]

I used a old 2N2712 I had left over from 25 years ago when I was
building PAIA 2700 modules from scratch (PAIA used a lot of 2N2712's).
It was weird - it would intermittently jump the noise level up by a
factor of ten for a second or so, then back down. I think that's called
"popcorn noise". Sounded horrible.  I replaced it with a 2N3903 and got
nice even noise, although I had to increase the gain (since it's a much
quieter transistor than the 2N2712).
Here's my noise source:
http://members.home.net/sbernardi/elec/og2/og2_noise_source.gif

harry wrote:

> Howdy...
>
> you reverse bias the base - emitter junction (for an NPN) by putting
> the
> positive voltage on the emitter and the negative voltage on the base.
>
> Selected 2N2712 were the favorites back in the 70's.  I just got a few
>
> brand new ones in surface mount. Maybe I can try one or two out....
>
> H^) harry
>
> "THOMAS, Mervyn" wrote:
>
>> IIRC the Z1J is(was) a noise diode - there was also a Z5J. I don't
>> think
>> they're available any more but you could use a transistor in its
>> place. I
>> can't remember which 2 pins of the TR you use (B-E || C-E) but I'm
>> sure
>> someone else on the list will have the answer to that one.
>>
>>
>> Merv Thomas
>> UNIX CAE SysAdmin - Portsmouth
>> *Email: mervyn.thomas at astrium-space.com
>> *Tel.:    +(0)23 9270 5394
>> * Fax.:    +(0)23 9270 8663
>>
>> -----Original Message-----
>> From: sandrotraversi [mailto:straversi at libero.it]
>> Sent: 26 November 2001 02:56:PM
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: [sdiy] Newbie & Zener D equivalents
>>
>>
>> Hi All,
>>
>> I'm a newbie and I'm trying to build a Noise Generator from an old
>> Practical
>> Electronic Sound Synthsizer modul
>> http://omega.tellus.vallentuna.se/anders/pdf/pess5.pdf
>> <http://omega.tellus.vallentuna.se/anders/pdf/pess5.pdf>
>>
>> The schematic needs a zener diode marketed in 1973 (!) by Semitron
>> Ltd as
>> Z1J.
>>
>> Which equivalent Z diode can I use in place of that ? ( possibly
>> available
>> in Italy) .
>>
>> 2nd Q - circuit needs also 2 caps about 0.01 uF - may I use
>> polyester type
>> or better ceramic disks ?
>>
>> Sandro
>>
>>
>>
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>>     --------------------------------------------------------------
>> IIRC the Z1J is(was) a noise diode - there was also a Z5J. I don't
>> think they're available any more but you could use a transistor in
>> its place. I can't remember which 2 pins of the TR you use (B-E ||
>> C-E) but I'm sure someone else on the list will have the answer to
>> that one. Merv Thomas
>> UNIX CAE SysAdmin - Portsmouth
>> *Email:mervyn.thomas at astrium-space.com
>> (Tel.:+(0)23 9270 5394
>> 2 Fax.:+(0)23 9270 8663
>>
>>      -----Original Message-----
>>      From: sandrotraversi [mailto:straversi at libero.it]
>>      Sent: 26 November 2001 02:56:PM
>>      To: synth-diy at dropmix.xs4all.nl
>>      Subject: [sdiy] Newbie & Zener D equivalents
>>      Hi All, I'm a newbie and I'm trying to build a Noise
>>      Generator from an old Practical Electronic Sound
>>      Synthsizer modul
>>      http://omega.tellus.vallentuna.se/anders/pdf/pess5.pdf The
>>      schematic needs a zener diode marketed in 1973 (!) by
>>      Semitron Ltd as Z1J. Which equivalent Z diode can I use in
>>      place of that ? ( possibly available in Italy) . 2nd Q -
>>      circuit needs also 2 caps about 0.01 uF - may I use
>>      polyester type or better ceramic disks ? Sandro
>>
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--
Scott Bernardi
sbernardi at home.net