Electrical Adjustments; Dolby Nr Adjustment - Pioneer CT-7R Service Manual

12. ELECTRICAL ADJUSTMENTS
Precaution
1. Mechanica.l adjustment should be completed.
2. Clean the following parts with an alcohol
moistened swab; Record/Playback head, pinch
roller, Erase head, Rubber belts and Capstan.
3. Demagnetize record/playback head with a head
demagnetizer.
4. Do not use magnetized screwdriver for adjust-
ments.
5. Adjustment and measurements should be per-
formed for both L-ch and R-ch with rated
power supply voltage.
Adjustments should be performed in the order
given in this service manual. Altering the order
can hinder proper adjustments, resulting in loss
of performance.
Level during measurements are based on
OdBv:1V. Connect a 50kO dummy resistor
across the OUTPUT terminals.
Let the CT-7R warrn up (aglng) for a few
minutes before proceeding with the adjust-
ment.
Set the DOLBY NR switch OFF unless direct-
ed otherwise.
Test Equipment/Tools Required;
1. Test tape
STD-331A
for general playback pur_
STD-341A
lo"rt"ptuyuu"t adjustment
STD-608A
NORMAL blank tape
STD-603
. .'CrO, blank tape
STD-604
. . METAL blank tape
Audio oscillator
AC millivoltmeter (AC mV)
Attenuator
Oscilloscope
Resistor 5OkSl (1/4W)
L E V E L ( d B }
I
6 .
12.1 DOLBY NR ADJUSTMENT
Step 1.
Setting:
Mode .
.. Record/pause
I n p u t S i g n a l
. . . . 7 O O H a - 1 0 d B v
(from INPUT)
( 3 1 6 m V )
AC mV meter 1 . . . .. . TP601 of the DOI.BY NR
assembly (L & Rch)
AC mV meter 2 . . . . . . TPG}2of the DOI"BY NR
assembly (L &Rch)
7 æ H r
l @ 8 !
1 3 1 6 n v I
7 .
8 .
L
^ h ç 2
r-J
'l-
TPbor \*_i/
|
t \ l
lutL_
- I -2 trClv
'1!lttrÈ!
2 .
3 .
4 .
5 .
6 .
o
-20
1OC) sec lO0 sec b0 sec 1OO sec
F i g . 1 2 - 1 C o n t e n t s o f t h e t e s t t a p e S T D - 3 4 1 A
a l
2 ? d A v
'e!2s^vtl
Procedure:
1. Adjust the INPUT level control so that the AC
mV meter 1 reads - 2.2dBv (ZZbmV).
2. Adjust the VR602 so that AC mV rneter 2
reads - 2.2dBv (775mV).
Step 2.
Setting:
Mode
. . Playback
I n p u t S i g n a l
. . . . 7 O O H z . - 1 0 d B v
(316mV) to TPIN of
the AMP assembly
A C m V m e t e r 1 . . . . . . T p 6 0 1 o f t h e m L B y
N R
assembly (L & Bchi)
AC mV meter 2 . . .. . . Tp602 of the DOLBY NR
assembly (L & BchD
Eg^
T m H z
! t u A v
l 3 l 6 m V l
,\
t ' v l
û
Procedure:
1. Adjust the ATT so that the
reads - 2.2dBv (Z?bmV).
2. Adjust the VR601 so that the
reads - 2.2dBv (TZbmv).
AC mV neter 2
AC mV $eter 1