Tektronix 570, Manual

Page: 30 / 134

out of regulation. The amount of current
which can be drawn in the reverse direction can
be increased by appropriate external loads
s uch as described under Thermionic Diode
Curves.
OSCI LLAT I O N OF D I S P LAY
Occasionally a tube will oscillate when placed
in the test socket. This oscillation will be
indicated on the s creen by obvious oscillation
o r by unexplained discontinuities in the display.
This will almost certainly occur if two tubes
are connected in parallel. For this reason,
parasitic-os cillation - suppression resistors
have been built into special patch cords and
ferramic beads have been installed on the leads
running from the tube socket on the adapter
panels. Usually the resistors in the patch cords
will prevent any oscillation if they are connected
to the control grid of the tube under test.
If the special patch cords are used, the effect
of any grid current which may flow should be
considered when evaluating the curves . The
ferramic beads are to prevent oscillation on the
display when displaying tube curves of high­
gain tubes.
2 - 1 2 Operating Instructions - Type
570 AA