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STR-DB840/DB940 SERVICE MANUAL US Model Canadian Model AEP Model UK Model STR-DB840/DB940 E Model Australian Model Chinese Model STR-DB940 Photo: STR-DB940 (AEP and UK models) (Black type) Manufactured under license from Dolby laboratories. "Dolby", "AC3", "Pro Logic" and the double-D symbol ; are trademarks of Dolby Laboratories. Manufactured under license from Digital Theater Systems, Inc. US Pat. No. 5,451,942 and other worldwide patents issued and pending. "DTS" an d "DTS Digital Surround" are trademarks of Digital Theater Systems, Inc. SPECIFICATIONS ­ Continued on next page ­ FM STEREO/FM-AM RECEIVER · Abbreviation AU : Australian model CA : Canadian model CED : AEP and UK models CN : Chinese model SP : E model U : US model 2 SAFETY CHECK-OUT After correcting the original service problem, perform the following safety check before releasing the set to the customer: Check the antenna terminals, metal trim, "metallized" knobs, screws, and all other exposed metal parts for AC leakage. Check leakage as described below. LEAKAGE TEST The AC leakage from any exposed metal part to earth ground and from all exposed metal parts to any exposed metal part having a return to chassis, must not exceed 0.5 mA (500 microamperes.). Leakage current can be measured by any one of three methods. 1. A commercial leakage tester, such as the Simpson 229 or RCA WT-540A. Follow the manufacturers' instructions to use these instruments. 2. A battery-operated AC milliammeter. The Data Precision 245 digital multimeter is suitable for this job. 3. Measuring the voltage drop across a resistor by means of a VOM or battery-operated AC voltmeter. The "limit" indication is 0.75 V, so analog meters must have an accurate low-voltage scale. The Simpson 250 and Sanwa SH-63Trd are examples of a passive VOM that is suitable. Nearly all battery operated digital multimeters that have a 2 V AC range are suitable. (See Fig. A) To Exposed Metal Parts on Set MODEL IDENTIFICATION ­ Rear View ­ Part No. Model DB940: US model DB940: Canadian model E model Chinese model Australian model DB940: AEP and UK models DB840: US model DB840: AEP and UK models DB840: Canadian model Part No. 4-227-151-0s 4-227-151-1s 4-227-151-2s 4-227-151-3s 4-227-151-4s 4-227-151-5s 4-227-151-7s 4-227-151-8s 4-227-151-9s 0.15 µF 1.5 k AC voltmeter (0.75 V) Earth Ground Fig. A. Using an AC voltmeter to check AC leakage. Notes on chip component replacement · Never reuse a disconnected chip component. · Notice that the minus side of a tantalum capacitor may be damaged by heat. Flexible Circuit Board Repairing · Keep the temperature of the soldering iron around 270 °C during repairing. · Do not touch the soldering iron on the same conductor of the circuit board (within 3 times). · Be careful not to apply force on the conductor when soldering or unsoldering. SAFETY-RELATED COMPONENT WARNING!! COMPONENTS IDENTIFIED BY MARK 0 OR DOTTED LINE WITH MARK 0 ON THE SCHEMATIC DIAGRAMS AND IN THE PARTS LIST ARE C