Michael Black wrote:
I gather those with HRO-500s have had some problem replacing germanium
transistors (and probably the germanium transistors need replacing because
they've gone bad over time).


Germanium transistors are cheap and plentiful on eBay. You need to figure
out which ones made in the Soviet Union replace the ones made in the west.

Germanium transistors were mostly PNP, so NPN ones are harder to find.

Replacements for CK722, 2n404, 2n107 and 2n109 are less than a $.25 each
including postage. I am sure there are others, but those were the ones
I needed.


I found 100 assorted Tesla (eastern Europe, not actually Soviet) ones
for less than $.50 each including postage.

Geoff.

--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379