sharp CD loader, tape and radio power problem

a friend of mine plugged his Sharp SD-GX2-s 110 volts AC into 220 volts. The small standby transformer blew, 2 other diodes also went bad. I detected and changed the transformer and the diodes. after switching on the power came but quickly the relay cut out with this message on the screen (b4 going off) Er MDRO . subsequent check shows a short zener diode the number on the board is D903. Identifying the part number on the diode is a problem. it reads something like 1N141.48 or 1N1418. I have cross check in a data book but no help. I would be v. glad if someone can help. Thanks

Reply to
fynnashba
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For a test, just remove the zener. Protection zeners often fail shorted. As long as yo plug into the right mains voltage, you can do without the diode during test. If everything works, measure the voltage, and solder in a zener of 2-4 volts higher.

Reply to
Sjouke Burry

That's sound advice if the zener in question has been identified as a shunt protection diode (actually pretty rare in audio equipment power supplies) but if it is the reference zener of a series regulator circuit, then removing it may well result in the full supply voltage being passed to the rail that is supposed to be being regulated down from it. Depending on just how high that is, there's no telling how much additional downstream damage may be caused by that action ...

Arfa

Reply to
Arfa Daily

Without a service manual/parts list, you need to determine what the exact markings on the component are.

A 1N4148, for example, is a commonly used small signal switching diode, not a zener type.

There are some 1N14xx numbers on this page, but no specifications

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-- Cheers, WB .............

Reply to
Wild_Bill

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