Studer-D731-cd-sn 电路图 维修手册.pdf

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1、Service NoteD730/D731 SN99-01 09.11.99 BND730/D731 SN 99-01Page 1 of 3 CD Player D730/731 Out-of-Speed Control Reason Recently, we finally discovered that the series regulator LM317 (IC 905) increases its output voltage when aging. The series regulator from National Semiconductor is heating up and c

2、ollapses. The voltage rises up to 12 Volts. Due to this fact, IC703 (HEF4750 on Mainboard 1.630.152.XX) is supplied with excess voltage and is damaged. To prevent this causal problem, we recommend to cool the regulator(s) as follow. Solution The regulators heat is dissipated by a heat sink, and IC 7

3、03 (frequency synthesizer) HEF4560 must be replaced, if having been supplied with excess voltage. At this occasion, we strongly recommend to add an other heat sink to the negative regulator (IC 903), too. By these actions, the chip temperature drops for both regulators. Modification 1. Unsolder the

4、series regulator LM317T (IC 905). Add a heat sink (50.20.0002) to a new LM317T (50.10.0104 - Motorola). Apply thermal compound, if available. Mount the heat sink with an Allen-head screw (21.53.9354) to the LM317. Do not cut the regulators terminals in order to avoid heat accumulation when mounted.

5、2. Reinstall the regulator to the PCB, leaving the terminal leads as long as possible. Take care that the heat sink is completely isolated from any component. Bend the regulators terminals carefully in such a way that the heat sink does not touch C913. 3. Add an other heat sink (50.20.0002) to the L

6、M337T (IC 903), as described above with LM317T. Usually, it is not necessary to replace the regulator LM337T (50.10.0105) by a new device (1), unless it is obviously defective. 4. Replace the defective IC 703 (refer to page 2 - HEF4750V, 50.99.0179) . Bill of Materials Spare PartStuder Order NumberR

7、eferenceCount Heat sink50.20.0002to IC903 and IC9052 Allen-head screw M3x621.53.9354to IC903 and IC9052 LM 317T Motorola50.10.0104IC9051 LM 337T (1 refer to item - 3.)50.10.0105IC9031 HEF4750V50.99.0179IC7031 RadioFans.CN 收音机爱 好者资料库 Service NoteD730/D731 SN99-01 09.11.99 BND730/D731 SN 99-01Page 2 of 3 Component Layout of PCB 1.630.152.20 and later RadioFans.CN 收音机爱 好者资料库 Service NoteD730/D731 SN99-01 09.11.99 BND730/D731 SN 99-01Page 3 of 3 Section of Circuit diagram of PCB 1.630.152.20 and later RadioFans.CN 收音机爱 好者资料库