Ampex 351 - Page 81

Step 3:
Step 2.
Step 3:
Step 4:
Step 4:
Step 5:
Step 5:
A
Step 6:
Step 6:
Record Amplifier Bias Adjustment
Record Level Calibration
Step 1:
Step 2:
8-8
Place the equipment in the record
mode at 714 ips tape speed.
NOTE
The reproduce level must be cali 
brated using standard tape before
89-0144
Issue A
Place
SWITCH
position.
Set the
SWITCH
Place the METER AND OUTPUT
SWITCH in the PLAYBACK position.
NOTE
Provided that the brand and type of
tape used is not changed, the BIAS
ADJUST capacitor 5C13 may be used
to reset the bias to a zero VU reading
on the VU meter with the METER
AND OUTPUT SWITCH in the BIAS
position whenever the unit is recali 
brated.
With a small screwdriver set the BIAS
ADJUST trimmer for a maximum
reading on the VU meter. Then adjust
the bias control clockwise until the
signal drops 14 db. Place the METER
AND OUTPUT SWITCH in the BIAS
position and note the reading on the
VU meter. With the METER AND
OUTPUT SWITCH again in the PLAY 
BACK position, turn the bias control
counterclockwise until the signal
again drops Vz db. Note the reading
on the VU meter with the METER
AND OUTPUT SWITCH in the BIAS
position. Set the bias at the median
of these two readings.
With the METER AND OUTPUT
SWITCH in the BIAS position, adjust
BIAS CALIBRATION control 5R24
for a reading of zero VU on the VU
meter.
Half Track and
Stereophonic
Equipment :
-14
NOTE
This adjustment should be made us 
ing the brand of tape that normally
will be used on the equipment.
NOTE
Erase current will be directly propor 
tional to line voltage and the vu meter
readings will reflect any changes from
the 117 volt a-c voltage.
Place the equipment in the record
mode.
Center the noise balance potentiom 
eter. When the user faces the front
panel, the slot should parallel the
face plate.
Set the oscillator frequency at 500
cycles per second (cps) with an out 
put of approximately 1 volt.
Place the RECORD LEVEL knob at a
position that will obtain an on-scalc
VU meter reading.
the
tn
METER AND OUTPUT
to the ERASE function.
INPUT TRANSFER
the UNBAL BRIDGE
Using a small screwdriver, set the
ERASE ADJUST trimmer on the back
of the electronic chassis to obtain
vu meter readings at 117 volt ac line
voltage as follows?
Full (Single)
Track Equipment?
NOTE
Bias is set at a specific wavelength.
It it is desired to set bias as 15 inch
tape speed, use a frequency of 1000
cps.
NOTE
Erase adjustment on stereophonic
recorders must be made with only
one amplifier in the record mode at a
time as false readings may be ob 
tained if both amplifiers are in the
record mode.