JVC MF-47L - Cassette Deck Circuit Board Adjustment

MF-47L/ML
3. Adjust screw () so that indication of V.T.V.M. will 2. Adjustment of Level Meter
become max.
When the azimuth adjustment standard tape is not
available, play a music cassette.
Make the treble sound optimum with turning the screw
4. After this adjustment, the screw @ should be locked 3.
with a bond.
If necessary, adjust playback level, recording bias
current, bias and trap etc.
After adjustment of Dolby Noise Reduction Level
was completed, adjust the VR303 (L) & VR304 (R) so
that the level meter indicates Cal (+3dB). (Refer to Fig.
14)
Playback level
1. Set SOURCE SELECT switch to “CASS”.
2. Set EQUALIZER switch to “NORMAL”.
3. Set DOLBY N.R switch to “OFF”.
4. Play the reference tape VTT-664, (1kHz), and adjust
VR301 (L-ch) and VR302 (R-ch) so that the level
meter will indicate OVU.
4. Adjustment of Recording bias and frequency
1. Connect a resistor 10022 to the earth side terminal
of R/P head in recording state, and connect AC
milivoltmeter to the both terminals of the resistor.
(Refer to Fig. 13)
R/P
Head
Fig. 12 Frequency
is counter
Cassette Deck Circuit
Board Adjustment Ac mitivatemete
Fig. 13
Item of Adjustment
1. DolbyNoise Reduction Level Dotby NR TP(L)(-2.5dBm)
2.
Level
meter
VR305
3.
Playback
Gain
Dolby
T.P(R)
VR306
VRSOT
4. Recording bias current (-2.5dBm) VR308 1301
5. Recording current
Equipment and measuring
instruments to be used
for adjustment
. VTVM (measuring AC in milivolts)
. Oscilloscope
. Oscillator
. Attenuator
Frequency counter
. Standard tape VTT-664 (1kHz 16mM/mm)
. C-60 Normal sub-standard tape
. 1002 Resistor
_
. DOLBY N.R. Level
1. Set SOURCE SELECT switch to “AUX”.
2. Set DOLBY N.R. switch to “OFF”.
3. Set the deck in recording mode.
4. Apply 1kHz_ signal of proper level (0.5V
approximately) to “AUX” input terminal.
. Adjust the front REC VOLUME so that the signal
level will be -24 dBm at the terminals of VR401
(t-ch) and VR402 (R-ch) respectively. (Refer to Fig.
14)
6. Finally adjust VR401 and 402 so that the level will
be -2.5 dBm at the DIN T.P. (L) and (R).
ao
10=
VR309
*VR303 *VR302 *VR301
VR402(-24dBm)
*VR304
VR401(-24dBm)
*These V.R. are positioned on the lower Circuit Board.
Fig. 14