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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Default Reasonable to try to sub power MOSFET's?

Hi, I'm working on a home theater receiver that has a blown MOSFET
(2SK3599-01MR) in one of the switching power supplies. I can't seem
to find a replacement from any of the sources I'm aware of.

I was able to find a datasheet on it, and I'm wondering if it's even a
reasonable idea to try to use that to substitute some other MOSFET for
it by comparing datasheets.

If this isn't a completely stupid idea, what parameter(s) would be key
for making such a substitution?

Thanks.
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Default Reasonable to try to sub power MOSFET's?

Mr. Land wrote:
[...]blown MOSFET (2SK3599-01MR)[...] I can't seem
to find a replacement from any of the sources I'm aware of.


Have you tried Igor's No-Spammers custom search?
http://groups.google.com/group/sci.e...utors+EXCLUDED
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Default Reasonable to try to sub power MOSFET's?


"Mr. Land" wrote in message
...
Hi, I'm working on a home theater receiver that has a blown MOSFET
(2SK3599-01MR) in one of the switching power supplies. I can't seem
to find a replacement from any of the sources I'm aware of.

I was able to find a datasheet on it, and I'm wondering if it's even a
reasonable idea to try to use that to substitute some other MOSFET for
it by comparing datasheets.

If this isn't a completely stupid idea, what parameter(s) would be key
for making such a substitution?

Thanks.


In my experience, if you enjoy Disney's firework displays, go right ahead
and sub for the original ... !!

Seriously though, I've never had any luck going down the substitution route
for power MOSFETs in switchers. It seems like no matter how close - or even
apparently better - you get a match on the quoted parameters of the
original, then if it doesn't try to take the retinas out of the backs of
your eyes at first switch on, it will try to melt the supply to your house
two days later ...

Others on here might have found differently ?

Arfa


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Default Reasonable to try to sub power MOSFET's?

On Mon, 21 Jan 2008 23:17:12 -0800 (PST) JeffM wrote in
Message id:
:

Mr. Land wrote:
[...]blown MOSFET (2SK3599-01MR)[...] I can't seem
to find a replacement from any of the sources I'm aware of.


Have you tried Igor's No-Spammers custom search?
http://groups.google.com/group/sci.e...utors+EXCLUDED


Nice! Thanks for posting that.
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Default Reasonable to try to sub power MOSFET's?

On Jan 22, 2:17*am, JeffM wrote:
Mr. Land wrote:
[...]blown MOSFET (2SK3599-01MR)[...] I can't seem
to find a replacement from any of the sources I'm aware of.


Have you tried Igor's No-Spammers custom search?http://groups.google.com/group/sci.e...rowse_frm/thre...


Thanks, I will have a look at that.


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Default Reasonable to try to sub power MOSFET's?

On Jan 22, 4:28*am, "Arfa Daily" wrote:
"Mr. Land" wrote in message

...

Hi, I'm working on a home theater receiver that has a blown MOSFET
(2SK3599-01MR) in one of the switching power supplies. *I can't seem
to find a replacement from any of the sources I'm aware of.


I was able to find a datasheet on it, and I'm wondering if it's even a
reasonable idea to try to use that to substitute some other MOSFET for
it by comparing datasheets.


If this isn't a completely stupid idea, what parameter(s) would be key
for making such a substitution?


Thanks.


In my experience, if you enjoy Disney's firework displays, go right ahead
and sub for the original ... !!

Seriously though, I've never had any luck going down the substitution route
for power MOSFETs in switchers. It seems like no matter how close - or even
apparently better - you get a match on the quoted parameters of the
original, then if it doesn't try to take the retinas out of the backs of
your eyes at first switch on, it will try to melt the supply to your house
two days later ...

Others on here might have found differently ?

Arfa


Thanks for that advice. I found the device listed on a manufacturer's
site
(http://www.fujisemiconductor.com/htm...des/mosfet.htm) and
it's listed with "related" devices with a small set of comparative
characteristics.

I'm (only) guessing that I(D) is maximum drain current, R(DS)on is the
maximum
drain-to-source resistance when the device is fully on, V(DSS) is the
maximum drain-to-source voltage, and Q(G) Typ would be expected
capacitance at the gate.

I was hoping that, since these specs are the only ones on this page,
and the page seems to be intended to help you choose a device for a
design,
that if I could find one of the other numbers that came in close, I'd
be OK.

But it sounds like I'm just asking for trouble. Thanks again.
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Default Reasonable to try to sub power MOSFET's?


"Mr. Land" wrote in message
...
On Jan 22, 4:28 am, "Arfa Daily" wrote:
"Mr. Land" wrote in message

...

Hi, I'm working on a home theater receiver that has a blown MOSFET
(2SK3599-01MR) in one of the switching power supplies. I can't seem
to find a replacement from any of the sources I'm aware of.


I was able to find a datasheet on it, and I'm wondering if it's even a
reasonable idea to try to use that to substitute some other MOSFET for
it by comparing datasheets.


If this isn't a completely stupid idea, what parameter(s) would be key
for making such a substitution?


Thanks.


In my experience, if you enjoy Disney's firework displays, go right ahead
and sub for the original ... !!

Seriously though, I've never had any luck going down the substitution
route
for power MOSFETs in switchers. It seems like no matter how close - or
even
apparently better - you get a match on the quoted parameters of the
original, then if it doesn't try to take the retinas out of the backs of
your eyes at first switch on, it will try to melt the supply to your house
two days later ...

Others on here might have found differently ?

Arfa


Thanks for that advice. I found the device listed on a manufacturer's
site
(http://www.fujisemiconductor.com/htm...des/mosfet.htm) and
it's listed with "related" devices with a small set of comparative
characteristics.

I'm (only) guessing that I(D) is maximum drain current, R(DS)on is the
maximum
drain-to-source resistance when the device is fully on, V(DSS) is the
maximum drain-to-source voltage, and Q(G) Typ would be expected
capacitance at the gate.

I was hoping that, since these specs are the only ones on this page,
and the page seems to be intended to help you choose a device for a
design,
that if I could find one of the other numbers that came in close, I'd
be OK.

But it sounds like I'm just asking for trouble. Thanks again.


Well, you might be ok. You seem to have the abreviations for the various
parameters down pat, so that's a good start. Before carrying out any repair
on it, you might want to check that the current sensing resistor in the
source has not also gone open. Check the gate coupling resistor for open.
Check the main input filter cap for poor ESR / low value. Check the main
primary side rectifier diodes for short circuit.If it uses a control chip,
check the startup resistor(s) for value, and the supply decoupling cap. If
the gate coupling resistor is blown, or even just open, suspect that the
chip is also damaged. If you can source one, replace the feedback opto as
well. Check the secondary side for short circuit rectifiers (but don't get
fooled by the fact that they are 'fast' types that read very low in one
direction anyway). Shorted secondary side reccies can place such a strain on
the primary side circuitry, that it results in a blown FET.

If you have access to a variac, you can check for chopper drive on most
supplies, by leaving out the FET initially, and 'scoping the output pin of
the control chip, using primary side rectifier "-" (main filter cap "-") as
a reference, but be careful of your 'scope grounding, and the fact that you
are very close to rectified line voltage when doing this. You can often get
the chip basically 'going' with no more than 30% line input voltage for US
110v or 15% for EU 230v, which makes the checking a lot safer.

If you can source the correct FET, and it's not too expensive, save the
postage and order two of them. You can be sure that the first one will go
bang again ...

Arfa

Arfa


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Default Reasonable to try to sub power MOSFET's?

Arfa is dead on about that resistor. The source resistor is about the
same thing as an emitter resistor to a bipolar. There is also usually
a zener from gate to source, it may be shorted and if it is the drive
circuitry might be fried. In fact if the source resistor is open the
drive circuitry is usually fried.

That's why we change fuses LAST.

Now as for a replacement. This is a switching FET. You must have the
same or better gain in case it is a self oscillator, switching times
must be faster or at least equal, not knowing what frequency it is
supposed to run at. That is after all the maximum ratings have been
met or exceeded.

Do not change case styles, especially to a metal tabbed one. It is not
only a pain in the ass but might be illegal. If you are doing this in
your basement it is unsafe. This is a hot side component. If it is all
plastic and you get the insulator kit, and put in a non all plastric
device, there could be an insidious shock hazard. You certainly blow
the UL or CSA or whatever rating, and if this is done at an ISO
certified company it is so close to illegal you can smell it. It would
certainly be grounds for dismissal. So if it is plastic, stick with
plastic.

Just remember, after all the Id, Vd all that max, even if the
replacement device meets that criteria there is still transconductance
and switching time. If you have higher gain and faster switching time
you should be alright. Of course use the right type of transistor.
Some are optimized for switching, you don't want the ones that are
optimized to be used in the linear mode, such as an audio output.

There is a safety factor, mainly keep the same case style. Other than
that you can always upgrade a semiconductor device (in the US) because
of a mandate in 1976 that safety of a product cannot depend on the
failure of a semiconductor device.

There were TVs with absolutely no high voltage shutdown circuits at
all, the idea was, well the horizontal output will fail before it gets
that high. Well some didn't.

Just recently I had a dog case where the other tech replaced a damper
diode. This application requires a 1200 V doide. He put in a 400 V
diode, and the thing lasted for like a month. He must have read the
numbers wrong or something, and then by chance got a diode that was
able to take it. When it came back he replaced the diode again and it
failed immediately. So did another.

I finally had a look, saw where it was and said wait a minute, you
can't.......I went to the computer and found out for sure, it was the
wrong diode.

But you can't count on it failing, that is the rule.

Check that continuity from the source to the negative end of the main
filter, then make sure it reads open circuit, or close, from source to
gate, positive probe on the gate. Follow the foil from the gate and
there will be a resistor, make sure that is not open, and check where
it comes from for a shorted condition between it and hot ground or the
Vcc or Vdd of the chip. It a transistor check if it is shorted.

Also with as much unplugged as you can unplug, check all the
rectifiers on the seconday side for shorts. Many times the current
limiting works fine when one of the output voltages is overloaded, but
I have seen more than one design where if one of those rectifiers is
shorted it does not work, letting it fry another chopper transistor.
Happened more than once, so it is worth checking.

At any rate, have fun with it. Good luck.

Also I would check anything that drives an optocoupler. Alot of times
that fails and leads to overvoltage, frying it. Run your eyes down the
foils from the pins, if there are any electrolytic caps connected,
check them.

After all of this, you might not have a fireworks display. I would
suggest firing it up on a variac, but there are alot of designs that
simply will not start that way, so forget it.

JURB
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Default Reasonable to try to sub power MOSFET's?

On Jan 22, 11:09*pm, wrote:
Arfa is dead on about that resistor. The source resistor is about the
same thing as an emitter resistor to a bipolar. There is also usually
a zener from gate to source, it may be shorted and if it is the drive
circuitry might be fried. In fact if the source resistor is open the
drive circuitry is usually fried.

That's why we change fuses LAST.

Now as for a replacement. This is a switching FET. You must have the
same or better gain in case it is a self oscillator, switching times
must be faster or at least equal, not knowing what frequency it is
supposed to run at. That is after all the maximum ratings have been
met or exceeded.

Do not change case styles, especially to a metal tabbed one. It is not
only a pain in the ass but might be illegal. If you are doing this in
your basement it is unsafe. This is a hot side component. If it is all
plastic and you get the insulator kit, and put in a non all plastric
device, there could be an insidious shock hazard. You certainly blow
the UL or CSA or whatever rating, and if this is done at an ISO
certified company it is so close to illegal you can smell it. It would
certainly be grounds for dismissal. So if it is plastic, stick with
plastic.

Just remember, after all the Id, Vd all that max, even if the
replacement device meets that criteria there is still transconductance
and switching time. If you have higher gain and faster switching time
you should be alright. Of course use the right type of transistor.
Some are optimized for switching, you don't want the ones that are
optimized to be used in the linear mode, such as an audio output.

There is a safety factor, mainly keep the same case style. Other than
that you can always upgrade a semiconductor device (in the US) because
of a mandate in 1976 that safety of a product cannot depend on the
failure of a semiconductor device.

There were TVs with absolutely no high voltage shutdown circuits at
all, the idea was, well the horizontal output will fail before it gets
that high. Well some didn't.

Just recently I had a dog case where the other tech replaced a damper
diode. This application requires a 1200 V doide. He put in a 400 V
diode, and the thing lasted for like a month. He must have read the
numbers wrong or something, and then by chance got a diode that was
able to take it. When it came back he replaced the diode again and it
failed immediately. So did another.

I finally had a look, saw where it was and said wait a minute, you
can't.......I went to the computer and found out for sure, it was the
wrong diode.

But you can't count on it failing, that is the rule.

Check that continuity from the source to the negative end of the main
filter, then make sure it reads open circuit, or close, from source to
gate, positive probe on the gate. Follow the foil from the gate and
there will be a resistor, make sure that is not open, and check where
it comes from for a shorted condition between it and hot ground or the
Vcc or Vdd of the chip. It a transistor check if it is shorted.

Also with as much unplugged as you can unplug, check all the
rectifiers on the seconday side for shorts. Many times the current
limiting works fine when one of the output voltages is overloaded, but
I have seen more than one design where if one of those rectifiers is
shorted it does not work, letting it fry another chopper transistor.
Happened more than once, so it is worth checking.

At any rate, have fun with it. Good luck.

Also I would check anything that drives an optocoupler. Alot of times
that fails and leads to overvoltage, frying it. Run your eyes down the
foils from the pins, if there are any electrolytic caps connected,
check them.

After all of this, you might not have a fireworks display. I would
suggest firing it up on a variac, but there are alot of designs that
simply will not start that way, so forget it.

JURB


Thanks for the great info - I learned a lot. Cheers.
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Default Reasonable to try to sub power MOSFET's?

I'm not sure if anyone will catch this reply, but I just wanted to
thank
all you folks again for all the info and guidance on this and other
questions I've posted recently.

Thanks to you, I now have a working 7.1 home theater receiver (now
to find a remote.)

I am grateful.
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