Pioneer RX-P840 Service Manual page 14

RX-P840
3. Adjusting the Operating Temperature Setting of the Fan Motor (VR7701)
This adjustment is necessary when 1C7403 (+12V
regulator), Q7301 and Q7302 (temperature sensors), or
VR7701 has been replaced, or when the entire split board
Assy of the Power Amp Module Assy has been replaced.
Wi Adjustment-Related Cautions
@ Make sure the heat sink has sufficiently cooled (is the
same as room temperature Ta.)
@ Once the power has been turned ON, make FAN
measurements and adjustments as quickly as possible. (If +12V
too much time is taken, the heat sink temperature will
rise, and the measurements will deviate from the Ta
measurement point.)
FRONT ASSY FOR 100W
START
R7712 [DLING
R7708
R7714
i Adjustment R77093
1. Connect a voltmeter between TEMP and TP (or between
1IC7702 terminals No.3 and 2). (Refer to Figs. 2—3 and
1¢7702
2-6.) R7710
2. Determine the fan motor operating temperature setting
by means of the following formula. (Tolerance is within R7711 =
+30mV.)
Formula: (85°C — Ta) x 19 (mV) VR7701 S—
Ta: ambient temperature (°C)
3. Adjust VR7701 so that the voltage between TEMP and @
io?
TP is the value obtained from the above formula.
77
Digital voltmeter or tester
For example:
when the room temperature is 25°C,
set value = (85 — 25) x 19 (mV)
Fig. 2—6
Adjustment of Operating Temperature Setting of Fan
= 1140mV (tolerance within +30mV). Motor
Note:
Adjustment during service should be +30mV, but if this
value cannot be obtained with the measuring instruments
used for adjustment, +50mV is acceptable.
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