Tube testers have always fascinated me.
Although it is easy to set up a simple test circuit to verify that the valves
you have are still working to their intended specifications, it takes quite a
lot of tinkering if you want to carry out more tests on a valve or if you
need to test different types. A test circuit for every test.
It is much more
convenient to have a single box that contains test circuits for all conceivable
tests for all types of valves you think you want to test.
Now it is possible to build a tube tester yourself, but you will have to
calculate the right operating conditions and expected readings from the data
sheets for every type of valve you want to test.
For a radio serviceman (including those in the Armed Services) it will save a lot
of time if the settings of such a box are easily made, and if a booklet
comes with it that states the settings and acceptable readings for all types.
By doing so, he can rely on the knowledge of the manufacturer of the tube
tester.
The Hickok I-177 is an American tube tester from WW-II.
This model has specifically been built for the US armed forces.
My specimen has a label “US Army Signal Corps” and the case
is painted olive drab.
It is a robust tester, offering gm (mutual conductance) and emission tests.
It has a limitation though: originally it can only test US tubes
from WW-II.
Newer types can be tested using an extension box, the MX-949 A/U Adapter
that contains 7 and 9-pin miniature sockets.
I don't have such an adapter, but it is easy to construct one.
This tube tester contains two rectifiers to supply the testing voltages:
- 83 mercury vapour rectifier as plate voltage rectifier;
- 5Y3GT vacuum rectifier for grid bias voltage.
The reason why I bought this type of tester was that I needed
to test the rectifiers in my B&K 700 tester.
And I wanted a tester that I could be easily adapted to test valves
that I have data for, but which are not in the tables.
The B&K 700 tester is
not easily used for that.
I bought this tester through an Internet auction site in January 2009.
The price was right, but I had to accept that the case was quite rusted.
When I collected it, the smell made clear that it had been stored in quite
damp conditions.
But I will try and make it work again...
