WEBSTER CHICAGO 79 - Page 33

WEBSTER
1
CHICAGO
BULLETIN 79P038
MODEL 79 AND MODEL 80
CONDENSED FACTORY TEST SPECIFICATIONS
Follow this simple routine and be certain that
the entire wire recorder is completely tested and
adjusted.
MECHANICAL
Motor — Shaded pole induction type. 18 watts
at 120 volts, 60 cycles Alternating Current ( no
load). Starting torque 1.7 inch ounces on 120
volts, 60 cycles A.C. at room temperature. Rotor
speed 1720 to 1740 RPM ( no load). All motor
leads No. 20 stranded, tinned copper wire with
Underwriters approved insulation.
Motor Tension — Tension on motor tension cam
follower ( Located on top surface of Motor Cover)
is by tension spring, tension is 20 oz. plus and
minus 1 oz. Adjustment is made by bending shear
form lug. At 18 oz. spring shall retract cam lever.
Shafts — Chuck ( supply spool) shaft and Drum
(take-up drum) shaft must be free running with
no brake pressure. Adjustments by nut under bot-
tom plate.
Speed — Speed of Take-up Drum when recording
or transcribing shall be 109 to 115 RPM.
Brakes — See sketch in this manual for care and
adjustments.
Slide — Be sure slide has a free up and down
motion without binding or lateral play. Make cer-
tain all leads allow slide to work free.
Recording Head — No lateral play. Should feed
wire to either drum or supply spool equidistant
between flanges.
Drive Wheel Pressure — Pressure of the drive
wheel tire in the " Run" position, on the Take-up
Drum should be from 7 to 9 oz.
Motor Shaft Pressure — Pressure on the idler
wheel in the " Rewind" position of the Motor Shaft
should be from 2 to 3 oz.
"Wow" — When recording or transcribing should
not be more than 1/2 of 1%.
AMPLIFIER AND PANEL
Limits — All limits are based on an Input Voltage
of 117.0.
Voltages — Record Listen Switch in Record posi-
tion, Voltages should be as indicated on Voltage
chart.
Power Consumption — Amplifier 46 Watts. Motor
18 Watts — Total 64 Watts.
"RECORD- LISTEN" SWITCH IN
"LISTEN" POSITION
Amplifier Check No. 1 — With output switch in No.
1 position and volume and tone control fully ad-
vanced, . 005 Volts at 1000 cycles is fed to grid
side of 68,000 Ohm — . 001 MFD equalizing net-
work. Check speaker for audible distortion and
rattle. Tap tubes for microphonic and possible
failure.
Amplifier Check No. 2 — With output switch in No.
2 position, volume and tone controls fully ad-
vanced, and signal applied as in above, output
voltage across an external 3.2 Ohm load should
be 2.2 Volt minimum, undistorted. If output volt-
age is greater than 2.2 Volts but distorted, the
volume control setting may be retarded until the
output wave shape is undistorted. This setting is
allright if the output voltage across the 3.2 Ohm
load is at least 2.2 Volts.
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