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: [email protected] <[email protected]> On Behalf Of [email protected]
Sent: Wednesday, October 22, 2025 11:38 AM
To: [email protected]
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