Dual C 839 RC Service Manual page 8

To check NF-record ing currence, the NF vo Itage may be measured
with filter on checkp. 1 and chekp. 2
Harmonic distortion
When recording at 333 Hz with 0 dB level (LED display), har-
monic distrotion K3
must not exceed 2% for Fe DIN tape and
must not exceed 3% for Cr02 DIN tape.
Erasure
RECORD, Cr02, supply 1 kHz at 0 dB (LED display)
Erasure (measured selectively) greater than 62 dB
Limiter
Set R 4121 and R 4121' Ion switchboard) to fully counterclock-
wise.
LIMITER ON, RECORD,
Supply 400 Hz at the DIN input (+3 dB LED display). Slowly
rotate R 4121 or 4121' clockwise until the LED displays indi-
cate 0 dB.
When the voltage is briefly increased 10-fold (20 dB) at the
input, lt should take between 4 and 6 seconds (decay time) for
the LED display to reach —10 d8.
Fade Edit
Insert a recorded cassette. Switch the tape selector switch to the
relevant position. When FADE EDIT is operated, the level must
fade out within 3 — 5 seconds and the tape must be fully erased
after 10 seconds.
With the MPX filter switched off and FADE EDIT key depressed,
set minimum voltage at the output using L 4002 and L 4002'.
Overall frequency responses
For Fe203 DIN tape and Cr02 DIN tape, the overall frequency
responses must be within the specified tolerances stipulated in
DIN 45 500, sheet 4.
Recordings must be made at —26 dB (LED display). The units
must meet the requirements of DIN 45500, sheet 4 with Dolby
NR.
MIZMIIMISIIIIIIIIIIIIIMINI111111112
BZNIIIIIZZIIIIII11111111111113.111111«
aniiINIMMILIMPRZEME1111.1
nal1111111131z5 1111 11
111.11111111111M
I
1111111111111311111 1111 11
1111113111111M
B311111111M111 1111.1111M1111111B1
M311111111M113131 1111•3111111111111»
1111111111111102/11111111111»1111111112113111
zwearadonnon nm Nm
31111111111113 IN 1111
MINI III
f(Hz)20
40 250
1000 6300 20000
Lower limiting frequency = 40 Hz, upper limiting fre-
quency = 12.5 kHz
0.1 mNm = 1 pcm
Supply friction: (basic brake)
Left reel
0.8 — 1.2 mNm
Right reel 0.6 — 1
mNm (without counter belt)
0.8 — 1.2 mNm (with counter belt)
Tape tension at the supply reel:
By means of slow braking of the reel in question (both direc-
tions)
7 mNm
Braking the motor at end of tape:
During play or rapid wind/rewind, the motor must stop imme-
diately when a wind spindle is braked.
Tape tension between the capstans:
The capstan leading at any time must run more quickly than the
trailer capstan. (Tested by means of wow measurement — Dual
cassette 3150 Hz).
Briefly brake the front pressure roller so that a tape loop is for-
med between the capstans. Tape speed must now measure 0.1 —
0.3 % higher than previously.
Static tests on C 839 tape drive
(Tape drive not connected)
Test point DC resistance ± 20 %
1. Magnetic heads
1.1 Record/playback head track 1
track 2
treck 3
treck 4
1 rg
00000000h
00000000
9
1.2. Erase heads
2. Tape drive
1
J 00000000000L
'0000000000001
2.1. Wind motor
At points 2.1 and 2.2.,
the motor must be turned
over very slowly at 1 rpm
and inspected for inter-
ruption IRco I
2.3. Tacho generator
12
9/7
340
n
6/4 340
n
5/7 340
S- Z
8/4
340
SZ
1/3 4.25 S-2
2/3 4.25
SZ
7/8 12/10.5&2
60/50
n
" This value must be
measured 10 times
per revolution of
the motor at mini-
mum angle of
rotation.
11/1
2.4. Solenoids
(Kaltwiderstand) = initial, cold resistance
M4
2/6 30
n
M5
3/6
2.5. Cassette compartment lighting
6/
20 —60
n
2.6. Safety levers/sensors
Ca ssette senso r
Record dafety lever 1
Record safety lever 2
without with
cassette cassette
CO
2.7. Ground line
Plug/rear printed < 0.2
SZ
circuit board
12/1
514-
4/4.
Safety regulations
Servicing work on electronic devices may only be carried out by
trained personnel. During servicing, the device should be driven
via an isolating transformer. The safety regulations stipulated in
VDE 0860 H should always by observed.
Amongst other things, the design characteristics of the device
must not be changed in a way which would reduce its safety (i.e.
covering panels, mechanically secured lines, Ieakage paths and air
gaps etc.). Replacement parts must be equivalent to original re-
placementparts and be correctly fitted. After repair work has
been carried out, you must ensure that all exposed conductive
sections carry no line voltage.
8