[Milsurplus] Germanium diodes

[mikea]

On Tue, Jan 22, 2008 at 10:50:20AM -0500, Ray Fantini wrote:
> Anyone have any ideas about the affects of age on Germanium
> diodes? starting to suspect that several of the diodes used in
> the 618S/ ARC-38 family of radios I have been working on are
> failing to provide sufficient voltage to work properly. they work
> in discriminator circuits to provide reference voltage to servo
> amplifiers. The newest ones are from 1959/60 so they are over forty
> years old and do not know if their internal resistance increased
> with age? 

I saw someone posting (here? elsewhere?) about why tunnel diodes of 
about the same vintage might not be as good as brand-new, because the 
dopant gradient might not be as sharp owing to diffusion over time.
It certainly seems possible to me that the same mechanism would affect
other semiconductors, though only those that depended on extremely 
sharp dopant gradients would show problems quickly. 

Can you try more recently manufactured silicon diodes with about the 
same characteristics, or perhaps one of the hot carrier diodes being
sold as "germanium diode equivalent"? 

Some folks have found that forward-biased hot-carrier diodes are
*extremely* sensitive, so if you can work out a way to bias one to
_just_ below the turn-on point, you might be very happy with the
results.

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin