Miscellaneous varieties of valves 1
|
This is a rat bag of valves which considering
the scarcity of ordinary types will all be now pretty rare
|
DLS19 Thermal Relay
|
 |
This is quite a rare thing
(meaning that I've only ever seen this one example).
With valved equipment it's advisable
to delay application of HT until valve heaters have reached normal
operating temperatures. Most equipments used rectifier valves
which of course need to warm up before they can pass current
and this delay ensures the rest of the valves would have time
to warm up also.
Once semiconductor diodes had
been commercially released and used in valved equipments there
was a problem. Turning on the mains switch would instantly result
in HT being applied to the valves. There had been devices prior
to this encapsulated thermal relay which had been used in military
equipment. These were thermal relays using a heating coil wrapped
around a bi-metal assembly carrying contacts. They were about
3 or 4 inches tall and about 2 inches wide and an inch thick
enclosed in a perforated metal case. Their delay time was partly
dependent on ambient temperature and they needed to be adjusted
with a screwdriver.
The DLS19 and similar devices
made the thermal relay easier to embody in an equipment and provide
a reasonably toleranced delay without the need for careful adjustment
and testing. This device operates on the equipment's valve heater
voltage and can be fitted alongside the valves. When the thing
expired or became unreliable it could be swapped without the
need for dismantling, soldering and adjusting like the previous
variety.
This example was designed to
switch up to an amp at DC and a couple of amps at AC |
|
24T12 Thermal Relay
|
 |
Having found one thermal
relay in my collection of valves, I found a second shortly after.
This type has a faster operating
time than the DLS19 See the specification |
ZM1175 Numeric indicator
tube, commonly called a "Nixie" tube.
|
 |
This example, kindly donated
by Donald Thomson is the Mullard ZM1175, which uses a wire ended
base. The valve has a set of numbers arranged in front of one
another and uses the neon glow effect to illuminate one of the
digits. They use an HT voltage to strike the neon and this is
applied to the particular digit to be displayed. Usually the
colour is red or orange.
The tubes were used extensively
in electronic test equipment and industrial equipments from the
50s until LED's took over. The latter are still occasionally
used, but in turn have given way to low power LCD displays. Another
type of display is a high-vacuum type that uses a filament and
was found in most VCRs.
Coupled with the development
of displays are the decoders needed to drive them. In particular
LED types normally employ segments, which are lit in a particular
pattern to display specific numbers. Special decoder chips that
convert either binary codes or one of ten address lines to illuminate
the required pattern of segments were used for many years, later
to be made redundant by including the necessary decoding into
processor chips that integrated many other functions. These make
use of a data bus that can route codes and commands around the
equipment. |
NSP1 Strobe Lamp
|
 |
Robert Holmes who used
to be kept busy at the Gem Mill works of Ferranti tells me that
the NSP1 was still made there at the tail end of valve production
in 1969 and is a "Strobe lamp" used in things such
as stroboscopes. I guess the modern equivalent of this type,
which must have been used into the 70's, is a flash tube filled
with Xenon. High power lasers are a distant relative of these
devices. I recently read an article in a very old electrical
engineering book about the different effects obtained when applying
a high voltage across a glass tube carrying a soft vacuum of
either plain air, traces of various metallic elements or rare
gases. From that science, which developed through experimentation
and trial and error, sprang fluorescent tubes, voltage stabilisers
and presumably this device. Until the discovery of the electron,
near the end of Queen Victoria's reign, scientists were hard
pressed to explain what they saw. One old chap who was a famous
physicist at the turn of the century hadn't got to grips with
new fangled electrons and was convinced that current flowed through
the gutta percha insulation of undersea telephone cables rather
than the metallic conductor. In terms of exactly where the current
flowed he wasn't too far off the mark. The majority actually
flowed in the outer skin of the conductor and hardly any in the
main body of the wire. |
VME4 Tuning Indicator
|
 |
Anyone that used to have
a good quality wireless will recognise this type of valve.
This one is on the rare side
as its got an old B7 base rather than the more common Octal style.
The top circular area lit up
in a rather nice shade of green, something like a newish snooker
table baize. With no signal the lit area was about 270 degrees
and as a station was tuned in the lower unlit section, which
was about 90 degrees started to get smaller until, if the signal
was very strong, closed right up.
There probably are very few
around now that light up with a decent colour because as the
valve gets older the original rich green gets weaker.
I read somewhere that decent
illumination can be restored. Was it baking in an oven or popping
in the microwave for 10 seconds? Maybe someone has tried this
and could let me know? |
Cold Cathode Indicator
Valve
|
 |
I have quite a few of
these things. The end of the valve has an array of little neon
elements which light up in a circular pattern. Its use was in
things like counters where the neons would be externally numbered
0 to 9.
The valve does not have a heater,
hence the description "cold". |
RG1-240A Mercury
Vapour Rectifier
|
|
This type of valve
was used to provide a high current at a high voltage.
This example is an RG1-240A
which has an anode rating of 2.2kvolts and can supply a maximum
rectified current of quarter of an amp. It's big brother the
RG3-1250 is rated at 8000 volts 1.25 amp.
The envelope contains mercury
vapour and when operating glows in the typical eerie greenish
blue colour of mercury vapour lamps used to light some streets.
Because mercury is considered
to be pretty dangerous the valve was rolled up inside it's box
in several yards of soft wrapping paper.
Judging from the note which
accompanied this example, this type of valve was not an easy
thing to use. The circuitry should have a delayed action relay
to prevent the HT supply turning on too early and the equipment
operator must have had to be pretty intimate with its pattern
of use!
A big problem was the heater
supply whose insulation needed to be up to the mark. |
Barretter
|
 |
I discovered this device,
looking like a festoon lamp, in a box of early radio parts. I
realised it was a barretter by the markings and then noticed
it had two markings. STC B1C/1E and at the other side CV433.
It's designed to produce a fixed defined current of about 1Amp.
The specification tells me it's a ballast lamp giving a stabilised
nominal current of 0.98 Amps over a voltage range of 3 to 9.5
volts with a spread of 0.88 to 1.07 Amps. As a lamp this equates
to 3 to 9.5 watts. |
|
|
|
|
|
|