[MRCA] Germanium Transistors

[scottjohnson1 at cox.net]

The characteristics are of minimal concern in a low frequency inverter, they
operate cutoff and saturated, so linearity is not really an issue. These
days, most of these inverters could be served by a single pair of power
MOSFETs. I don't think that is the point.  There is huge satisfaction to be
had making this equipment work as designed, within the bounds of reason.  As
far as "rot" goes, there was a problem with early Germanium semiconductors
with "purple Plague"  wherein gold bond wires on aluminum metallization
formed an intermetallic compound (rather than a true alloy) which eventually
destroyed the device by virtue of its poor conductivity and very low melting
point.  Aluminum wire bonds eliminated the problem.  However, I have dozens
of devices that are up to 70 years old that are still percolating along
(ARC-58, URC-32, AIC-10 intercoms, PRC-21s, etc.  Some devices do and will
fail, but don't write all of them off unless there is evidence of a real
problem.  Hope this sheds some illumination of the topic.

 

Scott W7SVJ

 

From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> On Behalf
Of rl.boltz at mhsdesign.com
Sent: Wednesday, October 22, 2025 11:38 AM
To: mrca at mailman.qth.net
Subject: [MRCA] Germanium Transistors

 

Do NOS germanium transistors get "rot" or go bad from age?  I need to
replace the invertors in a PRC-47 and I have 5 NOS original germanium
transistors.  All test vastly different. I expect variations as not matched
sets but these are WAY off.  I suspect at least 60 years old and maybe much
more.

 

Ron Boltz

K3tzj

 

 

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