[sdiy] Kurzweil power problems and bad diode?

[Simon Brouwer]

Hi Peng,

megaohm wrote:

>   I have a K2000 that has been non-working for a few years now. Turned
> on power. Blew fuse. Replaced fuse. Blew again.
> It seems others have seen this same problem. The only helpful thing I
> could find was the following post:
>  
> > Kurzweil uses linear power supplies. Chances are one or more diodes
> in the
> > bridge rectifier have shorted, causing AC to be fed to the DC smoothing
> > capacitors, which have a low Equivalent Series Resistance and look
> like a
> > near dead short at 60 hertz. This type of failure is likely and the
> probably
> > cause of blown fuses.
> > Diodes fail for two reasons: power surge and inrush surge at power on. A
> > surge arrestor may cure problem #1, but the best remedy for #2 is to
> avoid
> > frequent power cycling, thus reducing your chances of diode failure.
> > If it were my unit, I'd get a VOM and buzz out the diodes (after
> > disconnecting power and also the transformer secondary coil from the
> diode
> > bridge) and see which are shorted. They can probably be replaced
> with off
> > the shelf varieties available at Radio Shack, etc.
> > Failing that, it's off to factory service. And if it's a new unit under
> > warranty, that's the way to go.
>  
>  
>   Tested the diodes and three of them measure 0.530 or there abouts.
> One measures 0.0001 so I'm guessing this needs replacement.
> It is a 1N5401. I'm wondering if this might be the proper fix/ diagnosis?

You can be sure that the diode is blown, so it should be replaced
anyway. It is possible that the blown diode is not the primary cause of
the problem (it could have been blown due to the failure of other
components) but 1N5401 is not expensive, so it wouldn't  hurt to just
replace it and try if the unit works again.



-- 
Vriendelijke groet,
Simon Brouwer.

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