Salvaged from a "grand-daddy" valve oscilloscope - a Taylor Model 31A
Taylor Electrical Instruments were a designer & manufacturer of test equipment in England
The company was purchased by AVO in 1958 and eventually AVO (which was purchased by Metal Industries in 1959) was purchased by Thorn Industries. A lot of structural changes were occurring in the electronics industry at this time.
The equipment dates from the early 1950's! see the photograph to view this ugly beast in all its former glory.
After evaluation, I decided that full restoration of this Taylor scope was not a viable project so this is one of the parts I have removed, FULLY TESTED prior to removal.
Philips Miniwatt Valve
British made
Type: 5V4G
Classic coke bottle glass envelope design
Type code markings are:
ε358
A1
The first character, at first glance looks to be a 1 but looking more closely it appears to be a calculus symbol ε, meaning this valve came from the Marconi factory.
The world of type codes is tricky, have a look for yourself at:
http://www.audiotubes.com/mullcode.htm
Black plates
Mica top section
Shows very little use visually (and that would be right because I know the scope has not been turned on since around the mid 1970's)
But just looking at the tube doesn't tell you if it is working, so (in the absence of my valve testers - all have now been sold) I did this:
Left the 5V4G in circuit but no filtering on the output, no load - the old electrolytics were all shot, so I was looking at raw DC from the rectifier.
Wired in full wave configuration, 360-0-360V AC from the power transformer - it is advertised separately.
From cold, there is of course no voltage at the anode but suddenly as it warms up I had 290V DC and this is very quickly followed by reaching 410V DC and staying steady.
So this basic go/no-go tells me that the rectifier is working as it should.
But wait there's more....
This comes with a very special tube retainer "hat" - not one of your modern all metal jobbies, this is so cool to look at.
This hat must be one of cutest valve retainer setups I have ever seen!
It looks like a little old grannie's hat, with springs down each side.
The material is NOT metal but a sort of high temperature fabric, it certainly has not melted! In all my years I have never seen one of these before, very unusual.
See the photographs for this tube "in-situ" with the hat on her head.
