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

wrote:
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
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.

I think the 1N1418 is a Schotky diode:

'http://circuitspot.com/?m=201003]2010 March'

"Sjouke Burry" wrote in message
...
wrote:
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
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.

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

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
http://www.nowcomponents.com/item1/page.cfm/215

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


wrote in message
...
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