STR-DH540 (serv.man2) - Sony Audio Service Manual (repair manual). Page 2

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Check the surrounding circuit of power transistor (example:  Q600 on the MAIN board) and the surrounding circuit of  power amplifier circuit (example: FL on the MAIN board),  and exchange the defective parts. 

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Measure the power amplifier circuit (example: FL on the MAIN  board) with a tester, and check the following things.  1. Check that between the power supply line and the ground does 

not short-circuit. 

2. Check that resistance is normal. 

1. Check the R2140, R2141 Short or Open circuit?  2. Check Main Board +7 V Regulator. 

Check that voltage of the follow pin 2.8 V.  Digital Board: IC2100 Pin 99 (Fuse_Det) 

Check that the “PROTECT” is not  displayed on the fluorescent  indicator tube. 

Check that voltage of the follow pin 0.6 V.  Digital Board: IC2100 Pin 67, 68  

 

 

 (Temp_Sensor_1&2) 

Check that voltage of the following pin is 3.3 V.  DIGITAL board: IC2100 pin 92 (PROTECT) 

Check that the defect is not improved, even if you  do the following works. 1. Short-circuit the both ends of the C2186 on the 

DIGITAL board.

2. Perform the “SHIPMENT MODE” (refer to 

page 10 on the original service manual).

Check the IC2100 on the DIGITAL board and the  surrounding circuit, and exchange the defective  parts. 

Check the surrounding circuit, and exchange  the defective parts. 

Check that between the +59 V line/–59 V line and  the ground does not short-circuit. (Main Board) 

Check the surrounding circuit, and exchange the  defective parts. 

Measure the power transistor (example: Q600 on  the MAIN board) with a tester, and check the  following things.  1. Check that the circuit does not short-circuit.  2. Check that resistance is normal. 

Check the surrounding circuit of power transistor  (example: Q600 on the MAIN board) and the  surrounding circuit of power amplifier on the MAIN  board, and exchange the defective parts. 

Digital Board: Check R2115, R2134, C2164, C2165,     

Short to Gnd?

Main Board: Check TH251, TH252 

Check that the following fuses are not damaged. MAIN board: F912, F913 STANDBY board: F901 

Check that the power transistor (example: Q600 on the  MAIN board), the power amplifier circuit and the  surrounding circuit are not defect. 

Check that the surrounding circuit of current detect  (example: Q605 and Q604 on the MAIN board) is not  defect. 

Check the surrounding circuit of protector  (example: Q320 on the MAIN board), and exchange the  defective parts.