Ampex 351 - Page 83

Step 2; Step 2:
Step 3:
Step 4:
Step 5:
Step 6:
Step 7:
Step 8:
Record Noise Balance Adjustment
Step I:
8-10
Step 3:
Step 4:
If tolerances are not met, trouble-shooting
is indicated or the tape can be faulty.
Step 2:
Step 3:
NOTE
Models using 30750 or 30950 elec 
tronic assemblies utilize fixed equali 
zation.
Set the oscillator at 500 cycles and ad 
just the RECORD LEVEL control to
obtain a VTVM reading of approxi 
mately — 12 dbm (,195v).
Now place the METER and OUTPUT
SWITCH in the PLAYBACK LEVEL
position.
Make a frequency response check by
sweeping the oscillator through all
frequencies from 50 to 15,000 cycles.
89-0144
Issue A
NOTE
If the slot of the noise balance adjust 
ment is more than 45 degrees from a
line parallel to the plane of the face
plate, troubleshooting is indicated. If
the noise tends to null at either adjust 
ment extreme, it indicates excessive
leakage in capacitor 1C10, trouble in
the oscillator circuitry or magnetized
heads.
The high frequency response may vary with
tapes of different manufacturers. This machine
has been adjusted to give optimum perform 
ance within specification with an average tape.
The high frequency record equalizers 1C46 or
1C7 (depending on tape speed) may be ad 
justed to give the flattest possible response
with the tape you intend to use. Do not use
the playback equalizers 21130 or 2R3I to com 
pensate for tape variations. The bias setting
will also change the high frequency response,
especially at the lower tape speeds (3% and
7 1 / ’ ips ). Before adjusting the record equalizers
make sure the bias has been correctly adjusted
as previously described.
Position the RECORD LEVEL knob
fully counterclockwise.
Disconnect any input.
Plug a set of earphones into the mon 
itor jack and listen for the point of
minimum noise while adjusting the
noise balance control.
Place the METER and OUTPUT
SWITCH in the RECORD LEVEL
position.
Set the audio oscillator to 500 cps.
Set the record level to approximately
-20 reading on the VU meter for 3%
and 7W ips tape speed, -10 for 15 ips
tape speed.
Now place the METER and OUTPUT
SWITCH in the PLAYBACK LEVEL
position.
Note the position of the PLAYBACK
LEVEL knob for future reference.
Rotate the PLAYBACK LEVEL until
the 500 cycle plays back at a conven 
ient reference on the VU meter.
Sweep oscillator through the fre 
quency band checking response on
the VU meter.
Re-establish the PLAYBACK LEVEL
CONTROL setting by placing this
knob in its original position (sec Stop
6).
CAUTION
Changing bias may change the
RECORD LEVEL CALIBRATION and
may require re-adjustment as de 
scribed earlier in this section on "RE 
CORD LEVEL CALIBRATION."
Overall Frequency Response Using the
VU-Meter
Step 1: Thread blank tape along the pre 
scribed path.
CAUTION
For stereophonic equipment see
NOTES ON ALIGNING STEREO 
PHONIC EQUIPMENT.