"Michael Black" wrote in message
news:alpine.LNX.2.02.1702171429360.15904@darkstar. example.org...
On Fri, 17 Feb 2017, Jon Elson wrote:

Dave Platt wrote:


Thinking about it... I wonder whether those poor old transistors might
not just have been Plumb Tuckered Out?
Yes, that is another possibility I considered. If the module had been in
use for a long time, with no cooling, these are the highest power
dissipation of all the signal transistors in the unit. Always on at 23
mA.

I repaired an HP synthesizer that had about 400 Germanium transistors in
it,
and about a dozen had failed. I replaced them with Silicon transistors
and
then sold it on eBay before any more units went out.

I thought germanium transistors in general had a tendency to go bad over
time. They'd start leaking. Maybe manufacturing improved over time, but
then at some point, silicon took over completely, except for a handful of
uses. So you can't easily get replacements, because few germanium devices
are made now.

In the very early days, germanium transistors were epoxy potted - it wasn't
very moisture proof.

They've been much better since hermetically sealed metal cans.

If you're used to silicon, the leakage on germanium devices is going to seem
pretty dire anyway.