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Default Macbook pro PS gone phut.

My wifes MacBook Pro power supply went phut yesterday. If had a look
inside and a reasonably sized resistor has burnt out (about 4mm in
diameter).

Is there any point in just replacing the resistor or has something else
almost certainly blown as well (even if invisibly)? If so, what would be
the next most likely candidate? Bridge rectifier?

Tim


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Default Macbook pro PS gone phut.

On 7 Oct 2019 11:28:52 GMT, Tim+ wrote:

My wife’s MacBook Pro power supply went phut yesterday. If had a look
inside and a reasonably sized resistor has burnt out (about 4mm in
diameter).

Is there any point in just replacing the resistor or has something else
almost certainly blown as well (even if invisibly)? If so, what would be
the next most likely candidate? Bridge rectifier?

The problem can be with SMPSU's is that when they do go 'phut' they
can take a few bits with them, so if you replace one bit, it goes phut
again very quickly when powering back on.

A neighbour gave me his old / big Dell monitor because it was 'dead'.
I opened it up and noticed quite a bit of damage (burned devices and
tracks) on the SMPSU. Reading up on it it seemed people had spent
quite a lot of time replacing ever increasing numbers of components
because sometimes, getting all of the damaged bits replaced and the
PSU working again ended up costing quite a bit.

Not wanting to waste such time and money (on something quite
dangerous), I searched out and found a new PSU from China and just
swapped out the most important capacitors for the recommended /
quality branded ones and now I have a nice big monitor. ;-)

However, swapping out the actual PSU 'guts' might not be an option
with your particular PSU but the good news is that being fairly
expensive (Apple), if it is a known / common thing, someone out there
should have fixed it (Youtube)?

Cheers, T i m


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Default Macbook pro PS gone phut.

Does the machine still run on the battery? If so then I'd suggest you might
be better off getting a replacement psu.

Not knowing the circuit I could not comment further. I had a dell go down,
reason? Damaged cable from the psu to the laptop, it could be seen where it
had melted near the power plug on the computer itself, I imagine psus do not
like a sudden short across their output and something will give.
However you need to get yourself a meter and check a few things.
If I could see, I'd probably first decide if its a switch mode or not. The
give away is that it will have a tiny transformer, but if its analogue then
it will have a big heavy one. If its a switch mode then, personally I'd not
mess with it any more its knackered. However if its an analogue, which these
days is unlikely, take out the bridge and see if there is ac volts on the
transformer secondary, Put a battery across the bridge in either direction,
and measure the volts on the other two legs, It should be the same polarity
no matter which way around the battery is placed. If it is not then the
bridge is dead. Then you need to figure out what the circuit itself after
that does. Very old psus were simply a smoothing capacitor and that was it,
but I suspect there is at the very least some kind of regulator in there.

From your description though my feeling is that its fried quite a lot of
stuff. You need a manual.
As though, I suspect a switch mode, mostly these are bin it jobs.
Brian

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"Tim+" wrote in message
...
My wife's MacBook Pro power supply went phut yesterday. If had a look
inside and a reasonably sized resistor has burnt out (about 4mm in
diameter).

Is there any point in just replacing the resistor or has something else
almost certainly blown as well (even if invisibly)? If so, what would be
the next most likely candidate? Bridge rectifier?

Tim


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Default Macbook pro PS gone phut.



"Tim+" wrote in message
...
My wifes MacBook Pro power supply went phut yesterday. If had a look
inside and a reasonably sized resistor has burnt out (about 4mm in
diameter).


Is there any point in just replacing the resistor


Nope, those dont usually die by themselves.

or has something else almost certainly blown as well


Yes, almost certainly.

(even if invisibly)?


Very likely.

If so, what would be the next most likely candidate? Bridge rectifier?


That wouldnt normally see a power resistor fried because
the rectifier usually fails open circuit. More likely the main
ic controller that has failed in a way that has the switching
transistor on all the time instead of being switched.

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Default Macbook pro PS gone phut.

Brian Gaff wrote

Does the machine still run on the battery? If so then I'd suggest you
might be better off getting a replacement psu.


Not knowing the circuit I could not comment further. I had a dell go down,
reason? Damaged cable from the psu to the laptop, it could be seen where
it had melted near the power plug on the computer itself, I imagine psus
do not like a sudden short across their output and something will give.


The best designed ones handle that fine.

However you need to get yourself a meter and check a few things.
If I could see, I'd probably first decide if its a switch mode or not.


They all are now.

The give away is that it will have a tiny transformer, but if its analogue
then it will have a big heavy one. If its a switch mode then, personally
I'd not mess with it any more its knackered. However if its an analogue,
which these days is unlikely, take out the bridge and see if there is ac
volts on the transformer secondary, Put a battery across the bridge in
either direction, and measure the volts on the other two legs, It should
be the same polarity no matter which way around the battery is placed. If
it is not then the bridge is dead. Then you need to figure out what the
circuit itself after that does. Very old psus were simply a smoothing
capacitor and that was it, but I suspect there is at the very least some
kind of regulator in there.


From your description though my feeling is that its fried quite a lot of
stuff. You need a manual.
As though, I suspect a switch mode, mostly these are bin it jobs.



"Tim+" wrote in message
...
My wife's MacBook Pro power supply went phut yesterday. If had a look
inside and a reasonably sized resistor has burnt out (about 4mm in
diameter).

Is there any point in just replacing the resistor or has something else
almost certainly blown as well (even if invisibly)? If so, what would be
the next most likely candidate? Bridge rectifier?

Tim


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Default More Heavy Trolling by Senile Nym-Shifting Rodent Speed!

On Tue, 8 Oct 2019 05:56:42 +1100, AlexK, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:


Is there any point in just replacing the resistor


Nope, those don˘t usually die by themselves.


They CAN die by themselves, senile asshole! And he can easily give it a try
as they cost almost nothing.

or has something else almost certainly blown as well


Yes, almost certainly.


You don't know that, senile Ozzie pest!

(even if invisibly)?


Very likely.


You don't know that, senile Ozzietard!

If so, what would be the next most likely candidate? Bridge rectifier?


That wouldn˘t normally


You clinically insane senile idiot had better not use a word like
"normally"! BG

--
about senile Rot Speed:
"This is like having a conversation with someone with brain damage."
MID:
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Default Lonely Psychopathic Senile Ozzie Troll Alert!

On Tue, 8 Oct 2019 07:08:22 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


Not knowing the circuit I could not comment further. I had a dell go down,
reason? Damaged cable from the psu to the laptop, it could be seen where
it had melted near the power plug on the computer itself, I imagine psus
do not like a sudden short across their output and something will give.


The best designed ones handle that fine.


Oh, shut, you auto-contradicting senile ASSHOLE!

However you need to get yourself a meter and check a few things.
If I could see, I'd probably first decide if its a switch mode or not.


They all are now.


Shut it, finally, you auto-contradicting senile ASSHOLE!

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"Auto-contradictor Rod is back! (in the KF)"
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Default Macbook pro PS gone phut.

AlexK wrote:


"Tim+" wrote in message
...
My wifes MacBook Pro power supply went phut yesterday. If had a look
inside and a reasonably sized resistor has burnt out (about 4mm in
diameter).


Is there any point in just replacing the resistor


Nope, those dont usually die by themselves.

or has something else almost certainly blown as well


Yes, almost certainly.

(even if invisibly)?


Very likely.

If so, what would be the next most likely candidate? Bridge rectifier?


That wouldnt normally see a power resistor fried because
the rectifier usually fails open circuit. More likely the main
ic controller that has failed in a way that has the switching
transistor on all the time instead of being switched.


Okay. I guess Ill ditch plans to try and mend it. Ill keep the magnetic
power lead though as its in good nick and weve had one of these fail in
the past.

Tim


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Default Macbook pro PS gone phut.



"Tim+" wrote in message
...
AlexK wrote:


"Tim+" wrote in message
...
My wifes MacBook Pro power supply went phut yesterday. If had a look
inside and a reasonably sized resistor has burnt out (about 4mm in
diameter).


That doesnt appear to be burnt out from the later photo.

Presumably you mean its open circuit,

Is there any point in just replacing the resistor


Nope, those dont usually die by themselves.


But if its just open circuit, likely it would be worth trying.

or has something else almost certainly blown as well


Yes, almost certainly.

(even if invisibly)?


Very likely.

If so, what would be the next most likely candidate? Bridge rectifier?


That wouldnt normally see a power resistor fried because
the rectifier usually fails open circuit. More likely the main
ic controller that has failed in a way that has the switching
transistor on all the time instead of being switched.


Okay. I guess Ill ditch plans to try and mend it.


I'd replace the resistor if its just open circuit.

ll keep the magnetic power lead though as its in
good nick and weve had one of these fail in the past.


Yeah, they lead a pretty hard life,

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Default More Heavy Trolling by Senile Nym-Shifting Rodent Speed!

On Tue, 8 Oct 2019 09:05:40 +1100, AlexK, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:


Yeah, they lead a pretty hard life,


YOUR "life" on these groups will become even a lot harder, senile Rodent!
Wanna bet? BG

--
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"This is just a hunch, but I'm betting you're kinda an argumentative
asshole.
MID:


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Default Macbook pro PS gone phut.

On 07/10/2019 22:25, Tim+ wrote:
AlexK wrote:


"Tim+" wrote in message
...
My wifes MacBook Pro power supply went phut yesterday. If had a look
inside and a reasonably sized resistor has burnt out (about 4mm in
diameter).


Is there any point in just replacing the resistor


Nope, those dont usually die by themselves.

or has something else almost certainly blown as well


Yes, almost certainly.

(even if invisibly)?


Very likely.

If so, what would be the next most likely candidate? Bridge rectifier?


That wouldnt normally see a power resistor fried because
the rectifier usually fails open circuit.


Bull****.

Most failures on PN junction start as a loss of bakwards resistance due
to reverse breakdown - especailly under voltage spike cinditions. Only
if there is no fuse does what is now just a silicon resistor go open
circuit. With the magic smoke coming out
]


More likely the main
ic controller that has failed in a way that has the switching
transistor on all the time instead of being switched.


Okay. I guess Ill ditch plans to try and mend it. Ill keep the magnetic
power lead though as its in good nick and weve had one of these fail in
the past.

Tim




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€śThere are two ways to be fooled. One is to believe what isnt true; the
other is to refuse to believe what is true.€ť

€”Soren Kierkegaard
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