There are several types of tube-testers for the serviceman.
Simpson manufactures all different accepted types. Among
these, the Simpson Models 305 and 305RC are the most modest
in price. But this does not mean that they are limited in
performance of necessary functions. Such instruments are
simply not produced by Simpson, because Simpson does not
manufacture to sell at a price. First consideration is the
design of an instrument that will do a thorough job.
Simpson Models 305 and 305RC are designed to provide
accurate testing for all tubes with filament voltages from
.5 volts to and including 120 volts. It tests loctals,
single ended tubes, bantams, midgets, miniatures, ballast
tubes, gaseous rectifiers, acorn tubes, Christmas tree
bulbs, and all popular radio receiver tubes.
Like other Simpson tube-testers, the 305's incorporate 3-way
switching which makes it possible to test any tube
regardless of its base connections or the internal
connections of its elements. This method, the result of
exhaustive research and expensive construction, protects the
Model 305's against obsolesence. No adapters or special
sockets are required. In addition to having a complete set
of sockets for every tube now on the market, this tester has
a spare socket, to provide for future tube developments.
On the Model 305RC, the "No-Backlash" Roll Chart prevents
the chart from being torn or from getting out of alignment
by automatically keeping chart in constant tension. This
gives precision selection at all times. If you will remove
the Roll Chart unit you will see the very superior Simpson
construction throughout. It is, beyond question, the finest
roll chart mechanism, in design and in quality manufacture,
on any tube tester today.