Harman Kardon ONYX STUDIO 2 Service Manual ▷ View online
General Description of OS2 circuits
1.1 OS2 system structure introduction
The OS2 circuits mainly consist of 5 chips: AKM AK7742, SUNITECK BM153, TI TPA31162, TI
TPS54331, TI BQ24090, TI LM3478.
The SUNITECK BM153 (U300) is a BT module with PCM interface and it sent the data to AKM
AK7742 (U400)
The AK7742 (U400) is 24bit 2ch ADC +24 bit 4ch DAC with audio DSP, The stereo DAC and
ADC feature high performance, archiving 106dB and 96dB dynamic range respectively, 8kHz to
96kHz sampling rate are supported. The audio DSP has 1536step/fs parallel processing power,
and 74k-bit delay memory allows surround processing, acoustic effect and parametric equalizers.
As the AK7742 is a RAM based DSP, it is programmable for user requirements.
TI TPA31162 (U500/ U501) 50W Filter-Free Class-D Stereo Amplifier Family with AM Avoidance,
it has a small heat-sink attached to its top side Power Pad.
The TI TPS54331 is a 28-V, 3-A non-synchronous buck converter that integrates a low RDS-on
high side MOSFET to increase efficiency at light loads, a pulse skipping Eco-mode™ feature is
automatically activated.
The TI BQ24090 highly integrated Li-ion and Li-Pol linear chargers device
The TI LM3478 is high-efficiency low side N-Channel controller for switching regulator
Fig. 1-1 Block diagram of OS2 system structure
1.2 OS2 voltage test point
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Power supplies
TP600
BT_3.3V
Active state Nominal : 3.3V
TP601
+Vsys (Battery mode)
Active state Nominal : 11V
TP601
+Vsys (19V adapter mode)
Active state Nominal : 18.3V
TP602
AD+3.3V
Active state Nominal : 3.3V
TP700
+4.7V
Active state Nominal : 4.7V
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OS2 Key Component Placement
Fig 2-1 Top view of OS2 PCB placement
Faults Finding Chart
3.1 VBATA failed (TP705)
1. Connect good DC board/ USB board and KB to MB.
2. Set power supply 3.8V, connect to MB J700 and power on; monitor power supply voltage, if voltage
drop close to 0V, it must short at somewhere; otherwise go to next step
3. Measure TP701 voltage and it should equal to 3.8V; if not, J700 is defective.
4. Measure point VBAT voltage and it should equal to 3.8V; if not, R702 is defective.
5. Measure VBATA voltage and it should close to 3.8V, if not, measure Q702 pin3; Q702 pin3 is equal to
0V, Q700 is defective; if not measure BAT_ON OFF voltage and it should equal to 3.3V, if not, U300
BM153 is NG.
3.2. +12V failed (TP704)
1. Connect good DC board/ USB board and KB to MB.
2. Set power supply 3.8V, connect to MB J700 and power on; monitor power supply voltage, if voltage
drop close to 0V, it must short at somewhere; otherwise go to next step
3. Measure TP701 voltage and it should equal to 3.8V; if not, J700 is defective.
4. Measure U702 pin8 and it should close to 3.8V, if not R714/ R716 NG.
5. Take off L703 and measure point A voltage, if it still can’t get 11V on L703, it must be something wrong
in below circuit. Otherwise, it must short at some area, checking other part circuit which power is
coming from +12V.
3.3 +Vsys (TP601)
3.3.1 Battery mode
1. Connect good DC board/ USB board and KB to MB.
2. Set power supply 3.8V, connect to MB J700 and power on
3. Monitor power supply voltage, if it close to 0V, it must short at somewhere (3.1 and 3.2 part) else
R610 is defective
3.3.2 Adaptor mode
1. Connect good DC board/ USB board and KB to MB.
2. Set power supply 3.8V, connect to MB J700
3. Set another power supply to 19V/ 2A and plug in DC jack
4. Measure TP611 voltage and it should close to 19V; else DC board or J600 is defect
5. Measure point B voltage, if voltage close to 19V, D601 is defect; else it must be something
wrong for below component- C616, C617, C633, L606, C623, R622, C615, SX600
3.4 BT_3.3V/ AD+3.3V (TP600/ TP602)
1. Connect good DC board/ USB board and KB to MB.
2. Set power supply 3.8V, connect to MB J700 and power on
3. Monitor power supply voltage; if it close to 0V, it must short at somewhere else go to next step
4. Check U600 pin3 voltage is close to 1.9V or not. If not R602 or R605 is defective
5. Take off L600, measure point c voltage. If voltage is 3.3V, U300 circuit defect
6. Take off L602, measure point c voltage. If voltage is 3.3V, U400 circuit defect else U600 circuit is
defective
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