Roberts Valve & Circuit Analyser

 

 

Roberts Valve & Circuit Analyser

Another antiquity from my loft, given to me by the son of the engineer who once actually used it.
 

Cast you mind back to the TV and radio sets of the late 1940’s early 1950’s
There was no circuit board unplugging and replacing with a known panel back then

Most of the electronic products of the post war era were built on a steel chassis 16 gauge or 1.6 mm thick, 

with a dozen or more valves (tubes).  They were point to point wired with the occasional tag strip

There was no way a service engineer on a house call could take out the chassis to take voltage measurements, sometimes on console models it took two people to carry the set to the van.

Only simple Valve replacements were conducted in the home
Faulty sets were taken to the workshop
Where an engineer would narrow down the fault to an area

Which is precisely where the Circuit tester comes in handy?

Here is the tester in a Classic post War Pressed steel case

With 4 external toggle latches & leather carry handle

The instrument

Showing 2 panel meters 1 current & 1 voltage- Resistance

With selector switches to alter the range of the two meters
The main switch selects the Valve (tube) electrode you wish to measure

Inside Cover picture 

                                              

 Showing Umbilical Cable and a range of valve (tube) sockets, some missing

Operation

Imagine a set with no sound, start by removing the sound output Valve (tube),
Plug the tester umbilical cord into the tester, top left marked “Adaptor”
On the other end of the tester umbilical cord fit a suitable valve (tube)  pin adapter to suit the Valve you’ve removed.

Plug that valve adaptor in the Sets now empty Valve (tube) Base
While plugging the original valve (tube) you’ve removed into the correct socket on the tester

Switch the set on and hey presto   
Read the voltages on each valve pin and compare readings taken with those marked on circuit diagram

Note

There was a small internal battery to power the Resistance Test
Separate Voltage & current tests could be conducted with flying leads connected to the three Insulated Thumbscrew Cable Terminal posts
Marked Amps +,  Volts/ohms +   and Neg

This in now in my collection, my thanks go to Ewart , RIP