Electrical Adjustments; Test Equipments/Tools Required; Dolby Nr Adjustment - Pioneer CT-5 Service Manual

12. ELECTRICAL ADJUSTMENTS
hecaution
1.. Mechanical 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. Adjustments and measurements should be per-
formed for both L ch and R ch with rated
power supply voltage.
6. Adjustments should be performed in the order
given in this service manual. Altering the order
can hinder proper adjustments, resulting in loss
of perforrnance.
Level during measurements are based on 0dBv
= lV. Connect a 50kQ (47 - 52kO ) dummy
resistor across the OUTPUT terminals.
Let the CT-5 warm up (aging) for a few
minutes before proceeding with the adjust-
ment.
Set the DOLBY NR switch to OFF and TAPE
SELECTOR to the NORM position unless
directed otherwise.
Test Equipments/Tools Required:
1. Test tape
STD-341A . . For pl4ybrck adjustment
STD-608A
. . NORMS,II blasrk tape
S T D - 6 0 3
. . . . C r O z b f a n h t a p e
S T D - 6 0 4
. . . . M E T A t r , b l a n k t a p e
2. Audio oscillator
3. AC millivoltmeter (AC mV)
4. Attenuator
5. Oscilloscope
6. Resistor 50kC2 (47 - 52kf,2 )
F i g . 1 2 . 1 C o n t e n t s o f t h e t e s t t d p e r S T D - 3 t 4 1 A
7 .
8.
9.
12.1 DOLBY NR ADJUSTMENT
Setting
Mode.
. . Record
I n p u t S i g n a l . . . . . 7 0 0 H 2 , - 1 0 d B v ( 3 1 6 m V )
to LINE INPUT
A C m V m e t e r 1 - . . . .
. . . . .
T P 1 ( L c h , R c h )
of the Dolby assembly
AC mV meter 2. . . .
TP2 (Lch, Rch)
of the Dolby assembly
Since the left and right channels are identical, numbering
of the TP terminals of the Dolby assembly is applied to
both channels. When adjustment, please refer to Fig. l2-9.
Procedure
1. Adjust the INPUT level control so that the AC
mV meter 1 reads -2.2dBv (776mV).
2. Adjust the VR403 (Lch) and VR503 (Rch) so
that the
AC mV meter 2 reads -2.2dBv
( 7 7 6 m V ) .
3. Next set the CT-5 to the playback mode and
apply the
input signal (700H2, -10dBv;
316mV) to the TP1 (Lch) and TP2 (Rch) of
the mother assembly.
4. Adjust the attenuator so that the AC mV meter
2 reads -2.2dBv (776mV) and then adjust the
3 3
VR401 (Lch) and VR501 (Rch) so that the AC
mV meter 1 reads -2.2dBv (77drnV1.
Apply
the input signal (70OHz, -1OdBv;
316mV) to LINE INPUT.
Set the CT-5 to the record hode and connect
the AC mV meter to the R.O. {REC OUT) ter-
minal of the Dolby asse$bly. Adjust the
INPUT level control so thatrthe AC mV meter
reads -32.6d8v (23.4mV).
Set the DOLBY NR switch tD ON (C type)
position and adjust the att{rqftor
so that the
AC mV meter 1 reads -eZ.6Anf (2B.4mV) and
then adjust the VR402 (Lch) a4d VR502 (Rch)
so that the AC mV meter 2 treads -21.6dBv
( 8 3 . 1 m V ) .
I
>
R E C / F I B . h e a d
5 .
6 .
n
l .
Fig. 12-2 Head azimuth #juttment