Pioneer AS-LX70, Service Manual

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SX-LX70SW
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5.6 SPECIFICATIONS FOR THE PROTECTION CIRCUITS FOR THE DIGITAL AMPLIFIER
The protection circ u its for the Digital Amplifier are activated, following the specifications shown below. The error indication on
the FL display shows the reason a protection circ u it was activated.
Upon diagnosis of the Digital Amplifier, refer to the specifications for the protection circ u its here and the overview of the Digital
Amplifier circ u itry.
1. Overview
The system microcomp u ter monitors the ports for sh u tdown req u ests (Pin 3: /SD) and the ports for abnormal-temperat u re
detection (Pin 2 : /OT W ) of the Power Stage ICs (IC3201, IC3301, IC3401 and IC3501). As soon as any abnormality is
detected, it sh u ts the u nit down.
To notify the u ser of the possibility of a too high a vol u me, when the u nit is t u rned on the next time, the vol u me level will be set
to 0, and an error message will be displayed on the FL display.
2. Ports on the system microcomputer to be used for detection
Pin 77: SHUTDO WN
Low voltage at this pin means overc u rrent at the Power Stage ICs or that the power s u pply voltage for the gate
drive for the Power Stage ICs (= G V DD, Pins 1, 1 8 , 19 and 36), i.e., V G+12 is less than 10 V .
Pin 79: XOT W
Low voltage at this pin means the temperat u re at the Power Stage ICs exceeded 125
°
C.
Note: As one Power Stage IC is provided with two channels, fo u r Power Stage ICs (in total 8 channels) are mo u nted in
this u nit. For abnormality detection, the u nit implements a logical OR operation regarding these three ICs.
Therefore, which IC is abnormal cannot be known directly. To find which IC is abnormal, it is req u ired to check
whether abnormally detection is activated or not with the abnormality detection port of each IC open (by
temporarily removing a series resistor (IC3201: R3201, R3202, IC3301: R3301, R3302, IC3401: R3401, R3402,
IC3501: R3501, R3502)).
3. Detection timing
Start : Detection starts 500 ms after the P W RCO N T port (Pin 7 8 ) of the system microcomp u ter becomes active by yo u r
pressing the STA N DBY/O N key.
Finish : W hen the STA N DBY/O N key is pressed again (when the power-off process starts).
4. Operation of the protection circuits
The following three protection circ u its are activated when the conditions shown below are met:
Overc u rrent detection 1: Indication on the FL display: OC ERROR1
Conditions: If the SHUTDO WN ports, which are monitored every 10 ms, become low 7 times in s u ccession.
Overc u rrent detection 2: Indication on the FL display: OC ERROR2
Conditions: At the P.CO N FIG port (Pin21), which are monitored every 30 ms, 5.2A ( u com threshold 153) is fixed at
3000/6000 (MI N 1 8 0 sec/ MAX 270 sec).
Abnormal temperat u re detection 1: Indication on the FL display: O V ERTEMP
Conditions: If the XOT W ports, which are monitored every 10 ms, become low in s u ccession for one min u te.
Abnormal temperat u re detection 2: Indication on the FL display: O V ERTEMP
(Prereq u isite: The XOT W ports, which are monitored every 10 ms, become low three times in s u ccession.)
Conditions: The above prereq u isite is u pheld, and the conditions for an overc u rrent detection are met.
5. Process when the protection circuits are activated
The u nit is sh u t down within 30 ms after abnormality detection then the vol u me level is set to 0. The u nit can be t u rned on
immediately after the sh u tdown.