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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Zenith DVD Combo Home Stereo System
I have a Zenith DVD/Stereo Combo home theatre system. I bought it
about 3 years ago. It worked very well until recently. It made a pop noise while operating and the unit powered off. Now if you try and power up the reciever, it will emit a high pitch frequency for about half second and completely shut down. If you try and power it up again, nothing happens but if you unplug the unit, wait 2-3 minutes and plug it back in, the unit will enter standby mode and the red indicator light will be on. Then if you hit the power button to turn the unit into active mode it will emit the high freq. noise again and shut off. Any advice you can give me on what the problem could be and how to fix it would be greatly appreciated. Thanks, Craig |
#2
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Zenith DVD Combo Home Stereo System
wrote in message oups.com... I have a Zenith DVD/Stereo Combo home theatre system. I bought it about 3 years ago. It worked very well until recently. It made a pop noise while operating and the unit powered off. Now if you try and power up the reciever, it will emit a high pitch frequency for about half second and completely shut down. If you try and power it up again, nothing happens but if you unplug the unit, wait 2-3 minutes and plug it back in, the unit will enter standby mode and the red indicator light will be on. Then if you hit the power button to turn the unit into active mode it will emit the high freq. noise again and shut off. Any advice you can give me on what the problem could be and how to fix it would be greatly appreciated. Thanks, Craig Almost certainly caps in the power supply. Look for any with domed tops. They are very common as failures on the secondary side. If none look obviously bad, it will be necessary to check them with an ESR meter. Another possibility, if you heard a pop initially, is that one of the output ICs has failed, and is now loading up the power supply, causing it to go into shutdown. Often, the output IC's are on a separate board, with its own 3 or 4 pin power connector coming straight from the power supply. You can usually just unplug this, which will isolate any output IC problems from the supply board. If you are not used to working with switch mode power supplies, be very careful as they are not isolated from the line voltage, and are thus potentially very dangerous. Also, the main primary side resevoir cap can stay charged to a very high voltage on a non-functioning supply, for several hours - or even days in some cases. Arfa |
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