Pioneer M-790 Service Manual page 22

M-790
5.3 Adjusting the Operating Temperature Setting of the Fan Motor (VR7201)
This adjustment is necessary when [C301 (+12¥V regulator), Q7301 and Q7302 (temperature sensors), or VR7201 has been replaced, or when
the entire split board Assy of the Power Amp. UNIT has been replaced.
CAUTION :
Before performing this adjustment, short the blow trigger shorting pin (shown in Fig. 2) of the FRONT ASSY to prevent the protection
IC from malfunction. After adjustment is completed, remove the short-circuit.
Adjustment-Related Cautions
@ Make sure the heat sink has sufficiently cooled (is the same as 2. Determine the fan motor operating temperature setting by means
room temperature Ta.) of the following formula. (Tolerance is within +30mV.)
@ Once the power has been tured ON, make measurements and Formula : (75°C — Ta) x 19 (mV)
adjustments as quickly as possible. (If too much time is taken, Ta : ambient temperature (°C)
the heat sink temperature will rise, and the measurements will 3. Adjust VR7201 so that the voltage between TEMP and TP is the
deviate from the Ta measurement point.) value obtaind from the above formula.
For example :
@ Adjustment when the room temperature is 25°C,
1. Connect a voltmeter between TEMP and TP (or between IC7201 setvalue = (75-25) x 19 (mV)
terminals No.7 and 9). (Refer to Figs.6 and 7.) = 950mV (tolerance within +30mV).
Note :
Adjustment during service should be +30mV, but if this value can-
not be obtained with the measuring instruments used for adjust-
ment, t50mV is acceptable.
REAR ASSY 107201 :PROTECTION IC
@ [te For Tene aoe ss [97301 and Q7302 must be same hFE rank
= © 7 CN7104
TP7202 ec KM200SA2
QKF1002 { m| S
n| > +
Qo} - eal FAN
c\stizm [9 Sak. = MOTOR
ow be) oO ype
+12M o Wa AXM7003
M12V
N
7 aN
HSS104~-02
FA wn
So o % FAN STOP 12Vv
Digital Voltmeter
or Tester
o
EAN EO UME
0 FAN HI -11V |
ee
oo0000
Ne
PO
TP7201 7V
RKF1002
NO EC
g oe t
TP FOR TEMP ADs | ON. RIVE
D72n?7
ROS GES8?
RB4410-40
REF GND
712-BL/GR
Fig. 7 Adjustment of Operating Temperature Setting of Fan Motor
29