Heathkit TT-1 - Page 13

Position 1 - Cathode bus
Position 2 - Suppressor grid bus,
Position 2 - Plate Bie:
Position 4 - Screen grid bus,
Position 5 - Control grid bus,
Position 6 - Heater connection (high
Position 7 - Heater connection (oeround
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Position 8 - Space charge grid bus,
ca
2. oO
NS
The above listed positions are active when the
K, P and G switches are inthe#1 Position, With
these switches in the #2 Position, the cathode bus,
plate bus and control grid bus are switched to the
K, P and G positions of the SELECTOR switches,
PLATE Switch Positions
0- 26V DC
A - 20 V AC
B - 45 V AC
c-90V DC
D - 135 V DC
Q
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p>
BIAS Control and RANGE Switch
Range switch in L (low) position:
Ye
Control setting of 20 is approximately 2
volts, ete.
RANGE switch in H (high) position:
Control range is 0 to 20 volts negative.
Control setting of 10 is approximately 4
volts,
Vette
-
HEATHKIT
volts, etc.
SIGNAL switch positions:
1 - 2 volts RMS
2-1 volt RMS
4 - .5 volt RMS
The following example is based on the 6AU6 and
illustrates the steps involved in testing an un-
4 451. —_—
4
re
Reference to a tube manual (Specification
Sheet, Schematic Diagram, etc.) shows that
pin 1 of the tube is the control grid con-
nection. The SELECTOR switch corres-
ponding to this pin should therefore be
placed
in
the
control
grid
position
(Position
5).
Pin
2
is
the
suppressor
grid
connection;
the second SELECTOR switch is placed
in Position 2. Pin 3 is a heater con-
nection - SELECTOR switch to either Po
s Ww VLevs. CU
sition 6 or 7; Pin 4 (other heater connec-
tion) connects to the remaining heater po-
sition. Pin 5 is the plate connection - this
SELECTOR switch is indexed to’ Position
3. Pin 6 is the screen grid connection
(Position 4 on SELECTOR switch) and Pin?
is the cathode connection (Position 1). The
remaining two SELECTOR switches are not
used for a 7-pin tube and are therefore
placed in the 0 Position. The SELECTOR
switch setup for this tube would be:
52763-4100.
Set the FILAMENT switch to the proper
T+ s4h nw,
voltage or current position. If neither the
voltage nor the current canbe set exactly as
called for, use the next lower voltage value.
The 6AU6 would use the 6.3 volt position
of the FILAMENT switch.
Set the PLATE switch to the available
voitage nearest to that specified (always
use the lowest plate voltage that will pro-
duce a useable meter reading; in addition to
subjecting the tube under test to high plate
current, excessive plate voltage may givea
grid current indication on a good tube). The
"Typical Operation" chart for the 6AU6 lists
100 volts as the plate voltage; the PLATE
switch should therefore be set to Position
C (90 V DC). Page 13
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