JVC D-M3 - Main Adjustment; Nena Eeeeeeeeeeeeeeeeenes

Main Adjustments
[) Equipment and measuring instruments
used for adjustment
1. Electrical adjustment
1) Electronic voltmeter
2) Audio frequency oscillator
(range: 50—20 kHz and output O dB with impedance
600 0)
3) Attenuator
4) Reference tapes for playback (JVC test tape)
OA-A231 (for head azimuth adj.)
2.4 cm/s OA-W212 } (for motor speed, wow
1.2 cm/s OA-W221
flutter adj.)
OA-L212 (for reference level! 1 kHz)
TMT6438 (for music scanning)
TMT6439 (for music scanning)
5) Standard tapes for REC/PB
Normal OA-B111
Metal MC-60
6) Resistor
} or equivalent
6000 (for attenuator matching)
7) Band pass filter.
. Mechanical adjustment.
1) Torque testing cassettes
TW-1112A (for playback torque)
TW-1231A (for FF and REW torque)
2) Tape scanning cassette
MC-60
R/P Head
Fig. 16
D-M3 A/B/C/E/J/U
[I] Adjustment and repaire of the mechanism
(Adjust the mechanism or confirm that it is in normal
operating condition prior to the adjustment of the
electrical circuit.)
¢ Tape-to-head contact adjustment.
1) Turn the adjusting screw for aligning the erase head
until it stops. Then, turn the screw in the reverse
direction by 1.5 revoltion.
2) Check the tape-to-head contact using a MC-60 tape
having pads. ,
3) Check it again with a metal tape.
Checking method:
Record a 400 Hz or 1 kHz signal with OVU + 20 dB.
Erase the recording. Checking if the erasing is
satisfactorily performed.
4) After adjustment, apply screw bond on the adjusting
screw to prevent its loosening.
Semi fixed resistor for speed adj.
1.2 cm/S
2.4 cm/S
Fig. 17
Item
Adjustment
Adjusting
record/playback
head azimuth
No
. Connect an electronic voltmeter to the
LINE OUT terminals.
. Playback the OA-A231 test tape.
. Adjust the heal angle with the screw
@® until the reading of the electronic
voltmeter becomes maximum for both
channels.
. After adjusting, set the screw with
screw bond.
Adjusting Standard
point value
Maximum lf the head is worn, disconnected or
exceedingly magnetized so as not to
provide the necessary characteristics, replace it with a new one.
After replacement, the head position adjustment as well as the
playback level adjustment, the bias current adjustment and the recor-
ding level adjustment are all necessary.
If the output difference between the left and right channels exceeds
3—4 dB, the head is defective.
Replace it with a new one.
Remarks
No. 4213