A typical collection
of old valves
Occasionally, I buy or I'm offered
a collection of valves. Sometimes the types are intriguing and
a few days ago I received a collection from Chris Hampton of
"Hampton Colours" Stroud (see below). The valves once
belonged to his brother-in-law, a physics lecturer.
Below is the listing and, at
first sight the valves are fairly standard, however they're not.
Mostly collections are defunct TV valves put back in boxes belonging
to their new replacements; rarely they're all radio valves, but
in this case I suspect they were bought for things really technical,
maybe early computer equipment?
They total 48 in all and are
mostly what's termed "new old stock" with the 6060
and EAC91 being most prolific. The Brimar 6060 is classed as
a "special quality" ECC81, which often means it was
designed for much longer life. Although electrically similar
to the ECC81 it has smaller electrodes and despite being thought
of as an audio valve this particular version can be used at UHF
up to 500MHz. Some of the valves listed below are datewise quite
late and would represent examples from the end of the valve era.
At the end of my Electrical
Engineering course at Liverpool University in the early 1960s
I chose as my thesis a simple voice scrambler. This produced
two low-frequency-chopped amplitude modulated signals transmitted
on adjacent radio frequencies. To hear speech one needed two
radio receivers. The equipment was built on an aluminium chassis
and used mainly ECC81 valves. To make the project as legal as
possible I chose frequencies in Top Band.