Diode identification?

[Pooh Bear]

DaveC wrote:

Thus spake Pooh Bear:

I ask for a reason. Do you know the current draw on the supply ? It pays to
fit a beefier device if unsure.

Like this?:
http://www.nteinc.com/specs/500to599/pdf/nte580.pdf

I need it today and nte is the only maker available locally over-the-counter.

That ought to do it !

Who *are* these NTE ppl anyway ?

OH ! On account of it being a CT winding, you should also replace it's 'friend'
on the other half with the same type really.

Graham

 

[ian field]

"DaveC" <me@privacy.net> wrote in message
news:0001HW.C0878864000A76D1F02845B0@news.readfreenews.net...

Thus spake ian field:

Is "the other one" with 0.4Vf identical to the one you've taken out?

Yes, same markings. They're apparently a backward-connected set of
rectifiers
across a SMPS ct transformer secondary.

Thanks,
--
DaveC
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The 0.4Vf likely suggests a SB diode

 

[Arfa Daily]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4462443F.183E7ED7@hotmail.com...

Arfa Daily wrote:

"DaveC" <me@privacy.net> wrote in message
news:0001HW.C08779B30007055EF02845B0@news.readfreenews.net...
Thus spake Palindrâ~ťme:

Any chance of reverse-engineering the bit of the circuit it is used
in,
and
producing a bit of a circuit diagram?

Not very good at this... just a component-test monkey (c:

But it (and its partner) seems to be across a c.t. winding of the SMPS
transformer. Electrolytic filter caps "downstream" from these are rated
at
25v.

There are a dozen more of this type of diode in this SMPS, across other
trans. windings.

This is a multiple-voltage ps inside a 240v ac motor controller in a
Japanese
printing press.

Thanks,
--
DaveC
me@privacy.net
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Please reply in the news group

If it's on the secondary side, it will not be a 'normal' 1A diode. It
will
be a high speed Schottky type.

Not necessarily Shottky actually. ( btw - is it *meant* to have a 'c' in
it or
not ? )

Yeah, OK, it may well not actually be a diode with Schottky barrier
topology. I was using the term in a service engineer's generic way to
indicate a high speed fast recovery diode, as opposed to a low speed
grunting silicon junction diode - the OP's 'normal' diode that he speaks
of.

And yes, being named after German physicist Walter H Schottky, there is a "
c " in it ...

If you try to use a standard silicon
rectifier diode, it will run very hot and fail, in short order.


Oh I don't know. A subcontractor once fitted a 1N4004 where I'd specified
a
UF4004 on a lightly loaded secondary. It ran for many hours before failing
!

They did it second time round too ! I reckon that purchasing looked at the
part
number and reckoned they could substitute. Lovely stuff working with
Asians.

Funny thing was, my colleagues looked glum since it was our first smps
design. I
( in my infinite wisdom ! ) smelt a rat and went to it almost straight
off. It
was shorted. Just made the thing go into hiccup mode.

Graham

I reckon that the key to this one is that it was lightly loaded. A 1N4004
certainly won't stand up to SMPS frequencies for long, if loaded to more
than a few tens of mA. In fact I think you were very lucky that it did stand
up to it for as long as you say. Even the proper article fail regularly. I
change many secondary rectifiers that have failed short circuit in DVD
player switchers. Anyway, whatever. I stand by my original reply that the
diode will not be a 'standard' silicon one, and the fitting of a standard
one would likely result in short order re-failure.

Arfa