On Jan 1, 4:22*pm, "Arfa Daily" wrote:
"N_Cook" wrote in message

...





http://home.graffiti.net/diverse:gra...miniscope9.jpg

Made for ultra portability fits in an 8x11x 2.5 inch case when the
thyratron
and vibrator are removed from the chassis and stowed near the hinge. What
war time use was there for such a small 'scope, with in-the-field 12V
supply
capability?
War finish presumably means the off white enamel rather than black crackle
finish.
Plate on the brown casing lid
Miniscope
Miniature C/R oscilloscope
Pattern No 58259

Stencilled labels on the case are
R.L. 4
and No 1

Presumably somewhere would have info on the pattern number.
Even using "-dr who" googling does not find anything on Miniscope or that
pattern number, plenty on the 6K25 thyratron but nothing on 9 pin VR91,
10E/92 voltage regulator? or 9 pin CRT
VCR 522, 10E/787, Design Inspected CRT 4
(shattered probably when the shoulder carrying strap broke and corner
brace
broke off and split occured in the "suitcase" )
no other valves,
also Masteradio G650 12V vibrator, military trident symbol in a couple of
places , after an A on the VR91 and before a Z on the CRT
side panels missing, someone has crudely bodged in pot .

http://home.graffiti.net/diverse:gra...miniscope1.jpg
http://home.graffiti.net/diverse:gra...miniscope2.jpg
http://home.graffiti.net/diverse:gra...miniscope3.jpg
http://home.graffiti.net/diverse:gra...miniscope4.jpg
specs etc on hinge-down, prop-up plate
http://home.graffiti.net/diverse:gra...miniscope5.jpg
http://home.graffiti.net/diverse:gra...miniscope7.jpg

VR91 / EF50 was used in many wartime radios and early radar units (PPI and
pulse position). I owned a '1392 ex RAF vhf control tower receiver for many
years, and that was full of them.

Arfa- Hide quoted text -

- Show quoted text -

VR91/EF50 High gain pentode. Many of them were painted red. Some were
manufactured in the USA for Britain (I have one marked Sylvania').
They have a special 9 pin base. AIUI tube was based on a Dutch Philips
design.
Had always assumed they were a non-variable mu RF or IF pentode, which
were also used in some early mid-war aircraft radar receiver plug-in
units labelled RF24 through RF27 available on the surplus market after
WWII. But in a discussion some years ago on a group such as this, one
poster found the characteristics and pointed out that the tube did not
have a sharp control grid cut-off.
Cheers for 2009