Sony RM-785 Service Manual page 34

PVM-3230
RM-785
SECTION 4
SAFETY RELATED ADJUSTMENTS
CONFIRMATION METHOD
(HOLD-DOWN CONFIRMATION) AND
READJUSTMENTS (BR691)
The following adjustments should always be performed when
replacing the following components (marked with
~
on the
schematic diagram).
~
on FB BOARD: R67.5, R676, R688, R690, R691, R692.
R693, R694, R695, R696, R697, D698,
Q699, !C699
~ Oil
Dl BOARD: R534, R536, R538, Rl570, C509, 0503,
D508, D552, IC501, IC504
I. Input a monoscope signal.
2. Set PICTURE and BRIGHT controls to maximum.
3. Connect a digital multimeter to Pin
®
of FB-4 connector.
4. Confirm that the voltage is more than 15.3V DC.
5. Apply an external DC voltage gradually to TPJ on the FB
board, and when the voltage of Pin @ of FB-4 connector
becomes 18.951_
1
V DC, confirm the HOLD DOWN
circuit operates immediately and raster disappears.
When the HOLD DOWN circuit starts operating, switch
OFF the Power of the set immediately.
6. Turn the POWER switch ON, and apply an external DC
voltage gradually to TPl, and when the voltage of Pin ® of
FB-4 connector becomes 17.501· 1 V DC, confirm the
HOLD DOWN circuit does not operate.
If
the HOLD DOWN circuit operate, switch OFF the Power
of the set immediately.
7. Input a dot signal.
8. Set PICTURE and BRIGHT controls to minimum.
9. Apply DC voltage to TPl, and when the voltage of Pin® of
FB-4 connector becomes 19.85
::t
V DC, confirm the
HOLD DOWN circuit operates immediately and raster
disappears.
When the HOLD DOWN circuit starts operating, switch
OFF the Power of the set immediately.
10.
Turn the POWER switch ON, and apply
DC
voltage to TPl,
and when the voltage of Pin ® of FB-4 connector becomes
18.40
~2'
1
V DC, confirm the HOLD DOWN circuit does
not operate.
If the HOLD DOWN circuit operate, swithch OFF the
Power of the set immediately.
11. Input a dot signal.
12. Set PICTURE and BRIGHT controls to minimum.
13.
Confirm that the voltage of TP502 on the DI Board is more
than 133.0V DC.
14. Apply an external DC voltage to TP502, and when the
voltage becomes 141.68
±
0.5V DC, confirm the HOLD
DOWN circuit operates immediately and raster disappears.
When the HOLD DOWN circuit starts operating, switch
OFF the Power of the set immediately.
l.5. Tum the POWER switch ON, and when the voltage
becomes 138.50
±
0.SV DC, confirm the HOLD DOWN
circuit does not operate.
If the HOLD DOWN circuit operate, switch OFF the Power
of the set immediately.
16. When step 4 to 10 is not satisfied, readjustment should be
performed by altering the resistance value of
8
R691 on the
FB Board.
IB+ MAX VOLTAGE CONFIRMATION ( 8 R684
1
~685~
The following adjustments should always be performed when
replacing the following components (marked with
8
on the
schematic diagram).
Gil
on FA BOARD: RV65l, RV652, R664, R665, R670, R684,
R685, TH651, D663, IC602
1. Supply 130
:1
V AC, 60 Hz with variable auto-transformer.
2.
Input
a
monoscope signal.
3. Rotate RV651 on the FA board fully counterclockwise (B+
up}, and set RV652 to mechanical center.
Connect the regulated load to the following power supply
line.
+B (135V) line: FA-7 Pin(i). 800 mA (168Q) ... highlight.
4. Select temporarily R684 so that B+ voltage becomes about
135VDC.
5. Select R685 so that the voltage on Pin 0) of IC651 becomes
nearly 3.2
V DC
(less than 3.3V DC).
6. Rotate RV652 fully clockwise (B+ up).
7. Select R684 so that B+ voltage becomes 137 ~t l V DC.
fB+
ADJUSTMENT (FA BOARD)!
l. Adjust RV65 l so that B+ becomes 135
±
1 V,
2. Adjust RV652 so that the level
at Pin (l) of
IC651 becomes
3.2 ± 0.1\/
3. Repeat the adjustment until both (l) and (2) meet the
respective specifications.
4. After adjustment, fix RV652 with epoxy resin to lock
confirmly.
!CONFIRMATION WHEN REPLACING HVRj
Confinn that
the
voltage of Pin ® of FB-4 connector
is
more
than !5.3V DC when replacing HVR.
--36-
digital
multimeter
regulated-de
power supply
~--
l
--37--
PVM-3230
RM-785
digital
multimeter
,---'----'---;li
~
I I '
I
digital
multimeter
regulated-de
power supply
foc5l
L___;_9.J
~
PVM-3230
RM-785
--38 --