Akai GX-221D User Manual

.REC.BIAS ADJ. LEFT_CH.REC. BIAS ADu.
RIGHT ES06 TOP TC505 7OP
ait
Fig. 28 OSC. P.C. BOARD (Face Side)
4. RECORDING LEVEL ADJUSTMENT
1) Connect an Audio Frequency Oscillator to the line
input terminals through an attenuator, and con-
nect a high sensitivity V.T.V.M. to the line output
terminals.
2) Set both the Tape Speed Switch and the Equalizer
Switch to 7-1/2ips (19 cm/sec), depress the
STEREO Track Selector, and set the Monitor
Switch to TAPE position.
3) In case of model GX-225D, set Noise Reduction
Switch to OFF position.
4) Set Recording Level Controls to maximum and
load a blank tape (AKAI 100L Tape).
5) Set recorder to recording mode, and supply a
1,000 Hz signal from the Audio Frequency Oscil-
lator. Adjust attenuator to obtain a V.T.V.M.
indication of 4 dB.
6) Set Monitor Switch to SOURCE position, and
adjust Rec. Amp. P.C. Board recording level
adjustment semi-fixed resistors VR301 20kB
(Left Channel), and VR301b 20kB (Right
Channel) shown in Fig. 20 to obtain a V.T.V.M.
indication of 4 dB on both channels.
5. RECORDING BIAS FREQUENCY
MEASURING METHOD
Method I
1) As shown in Fig. 27, install a 1 to 2 Q resistor in
series with the recording head and connect the
vertical input of an oscilloscope to these terminals
(a and b).
2) Supply a sine wave signal from an Audio Fre-
quency Oscillator to the horizontal input of the
oscilloscope.
Fig. 29 OSC. P.C. BOARD MS-5025 (Reverse Side)
3) Set the recorder to recording mode, and vary the
oscillation frequency of the Audio Frequency
Oscillator until the waveform of the oscilloscope
displays a circular or linear pattern.
4) At the time of a circular or linear pattern display,
if the audio frequency oscillator indication is
within a range of 100 kHz +5%, the recording bias
frequency is correct.
Method 2
As shown in Fig. 27, connect a frequency counter to
terminals a and b, set recorder to recording mode,
and take a frequency counter reading.
. RECORDING BIAS VOLTAGE ADSJUST-
MENT (Frequency Response Adjustment)
1) Employ the same measuring instruments used in
Recording Level Adjustment procedure and con-
nect them in the same way.
2) Foollow Recording Level Adjustment procedure
through Item 5), and then set the attenuator to
—20 dB.
3) Under these conditions, adjust OSC P.C. Board
recording bias voltage adjustment trimmer con-
densers TC505 70P (Left Channel) and TC506 70P
(Right Channel) shown in Fig. 20 to obtain an
equally flat response at 1,000 Hz and 10,000 Hz.
4) Recording bias voltage, following frequency res-
ponse adjustment, is from 1.3 to 1.4 V A.C.
5) Ideal erase voltage is 70 V A.C.
NOTE: The frequency response will vary depending
“upon the tape being used. As a rule, AKAI
100F Tape (Fuji F tape) is used for this
adjustment.
21

Akai GX-221D Specifications

General

Brand	Akai
Model	GX-221D
Category	Tape Deck
Language	English