- Single trace
- 3 Valves (CV138, 5Y4G plus one unknown)
plus SenterCel E.H.T. rectifier
Initially this was a bit of a puzzle. From the outside I
wondered if this was a little scope perhaps used by the military. However,
opening it up shows that it is more like a home built effort - in fact,
a poor home built set.
The circuitry is pretty minimal, with no timebase speed switch just a variable
pot, so I assumed it was a homebrew effort from one of the period magazines
such as Practical Wireless. However, thanks to site visitor Ian Shorrocks
the true origin of the little 'scope is this :-
"The 1950s homebrew oscilloscope is not a homebrew. You may observe
that from the outside at least, it looks rather military in construction.
It is in fact an apprentice piece. I believe that it was designed by (what
was then) the Radar Research Establishment at Malvern in Worcestershire.
Every apprentice at that establishment built one. It was a cheapish design
intented to teach the fundamentals equipment construction and of oscilloscope
usage and characteristics (hence the simple design and the odd front panel
connections). It had little other practical use because of its simplicity.
It was known as the 'Malvern Oscilloscope'. "
"It spawned a mark 2 design which it was my lot to build when I was
an apprentice. By this time the Mark 2 design had been adopted throughout
the Government establishment apprentice schemes. The Mk 2 used a DG7 tube;
two EF91s (actually the one I built used CV4014s), and a rectifier, whose
number I cannot remember (6X7?). The EHT rectifier was still a selenium
"You are quite lucky to find one because although thousands were built,
once built they were almost immediately taken apart again; the salvageable
parts recovered and recycled a year later into another Malvern Oscilloscope."
"In my establishment, the design was later abandoned in favour of a
more complex design based on the 3 inch Heathkit model (actually it was
a straight rip off). By this time apprentices were allowed to buy their
work for the cost of the salvageable parts and it was felt that by producing
a useable design, they would be bought and save on paying someone to take
them apart. It largely worked and many an apprentice picked up a useful
tool for about £20 or so (the price was based on commercial valve prices
and not the special quality valves (CV4000 series) that were actually used).
||Dirty. And if you think I'm gonna switch on a 50's kit in
a metal case and no earth you can think again !
||£2 from the Radiophile's March 2002 auction at Wetwood.
Not much to see really, though the big 5V4G rectifier
occupies more than its fair share of space.