On 02/17/2017 02:31 PM, Michael Black wrote:
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.
Michael
Point contact devices especially.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net