[sdiy] Zener issues (again)

[Rutger Vlek]

Could it have been a difference in the capacitance of the zeners? I recall
discussing zener capacitance with Ian Fritz as we both ran into it when
designing the saturation stage of a filter and had problems with HF
tracking of self-oscillation.

Rutger

Op ma 30 nov. 2020 09:39 schreef David G Dixon <dixon at mail.ubc.ca>:

> Well, it was the zeners.  I swapped the old ones in and the circuit worked
> perfectly.  What a shit-show.
>
> I think maybe I'll order some 1N5231s instead.  They are rated for half the
> power dissipation, so they should all work, right?  Right?  Plus, Newark
> has
> Vishay ones on sale for $0.03 apiece.
>
>
>
> -----Original Message-----
> From: Roman Sowa [mailto:modular at go2.pl]
> Sent: Sunday, November 29, 2020 11:56 PM
> To: David G Dixon; 'synth-diy mailing list'
> Subject: Re: [sdiy] Zener issues (again)
>
> [CAUTION: Non-UBC Email]
>
> It's not the first time that you write here about counterfreight parts.
> Maybe you should consider changing regular parts source?
> 1W and 5W zener definitely need different package, so the mistake was made
> on the die level. If it wasn't checked before packaging, it could have been
> some small garage IC maker deep in China forest. Or rice field, China does
> not have much forest I think.
>
> Make one measurement - voltage at the test current shown in datasheet that
> is 49mA for one and 240mA for the other diode. You'll know for sure.
> BTW, when I searched for datasheets for them, it showed up about 20
> different brands making those diodes, and I have never heard of any of
> them.
> That sort of tells you what kind of reliability and repeatability to
> expect.
>
> BTW2, instead of 5.1V zener you can use 5V R-R opamp for clipping
> trapezoids
> and it will work much more precise, plus free buffering.
>
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