If the tube was multi section tube, there would be asecond and possibly
athird list of settings on the chart to test the additional sections. See Fig- 8.
Tube Type Heater “A” “B" ilQtf socket He.
6BN8 635 682
635 612
635 662
Figure 8.
SERVICE INSTRUCTIONS
The sensitivity of the grid emission test circuit is adjusted at the factory
so that aleakage of 25 megohms just reads in the “Grid Emission-Reject” area
on the meter scale. This order of sensitivity is the level that tube manufacturers
recommend, in order not to reject good tubes. The adjustment of this sensitivity
is ascrewdriver adjustment available through asmall opening just above and
to the right of the Quality button. This adjustment is made in the following
manner.
Place switch “B” to position 6, and switch “C” to position 1. Connect a20
megohm resistor between Pins 1and 7of socket No. 1, push Grid Emission
button, adjust the control for areading of 20 on the meter. If you wish to
make the Grid Emission test at greatly increased sensitivity, the following
adjustment will give you asensitivity in excess of 100 megohms. Place switch
“B” in position 6and switch “C” to position 1, push Grid Emission button and
with no resistor in the socket adjust the Grid Emission Sensitivity Control so
that the meter just reads zero.
This instrument has an internal adjustment for sensitivity of the short test
circuit. This control has been set at the factory for anominal 1megohm sensi-
tivity. This should be checked occasionally by placing a1megohm resistor be-
tween pin #3 and pin #8 of socket #8 with the Bswitch at 6and the Cswitch
at 3. Should this sensitivity control require re-adjusting, proceed in the follow-
ing manner:
1. Remove panel from case.
2. Locate short sensitivity control which is across the short lite socket base.
3. Place 1meg external resistor in test socket as outlined above. Rotate con-
trol so that the short lite just comes on, starting from end of control
where lite is out.
4. Re-assemble tester, be sure to remove 1meg resistor before testing tube.
The enclosed schematic diagram shows all voltage readings for the
instrument and the parts list is printed on the back of the schematic diagram.
In order to keep your tube chart up to date, it is recommended that you
subscribe to the B&Kchart mailing service at acost of $2.50 per year. This
service will provide mailings every 90 days. Two mailings will consist of com-
pletely new charts and will occur in January and July. In addition, in April
and October supplementary sheets will be mailed listing only the additional
new types which have come out since the last complete chart was mailed. This
will mean that within 90 days of the introduction of anew tube type you will
automatically have the information on how it is tested in your B&K
Tube Tester.
If you do not wish to use this “4 times per year” subscription service, the
latest available chart may be obtained at any time by remitting $1.50 to the
factory with the Model and Serial Number of your instrument.
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