PSU ?

I've repaired thousands of machines and once in a while have seen a
failed power supply take out a motherboard.

Only once though have I seen the hard drives taken out.

It was with a good quality supply and I thought it was just a very odd
fluke.


Last night I talked to someone who had also had it happen ,....so my
question is:


Does any manufacturer have a supply with fully surge-protected OUTPUT?


I assumed they all did.

On Wed, 26 Jun 2019 09:27:25 -0400, philo wrote:

Does any manufacturer have a supply with fully surge-protected OUTPUT?
I assumed they all did.

Not well enough to handle a lightning strike. I had a strike kill the mb,
ps, and two of three hard drives.

The lighting had hit a transformer across the street. Enough power came
through to kill that computer. I've since purchased a ups system. While
it protects against short term power loss, gives time to shut down safely
for longer period losses, and filters out the variations in voltage, etc.,
I haven't had another lightning strike like that one, so don't know if it
is enough to protect from that or not. It also killed all of the
incandescent light bulbs that were on at the time, and tripped all of the
circuit breakers that had any power going through them.

I'd expect the protection in a desktop computer's power supply to protect
from minor variations in voltage, but not much else.

Regards, Dave Hodgins

--
Change to for
email replies.

philo wrote:
I've repaired thousands of machines and once in a while have seen a
failed power supply take out a motherboard.

Only once though have I seen the hard drives taken out.

It was with a good quality supply and I thought it was just a very odd
fluke.


Last night I talked to someone who had also had it happen ,....so my
question is:


Does any manufacturer have a supply with fully surge-protected OUTPUT?


I assumed they all did.

There is a schematic of a basic ATX supply here.

http://www.pavouk.org/hw/en_atxps.html

That one has overvoltage protection -- it stops Q1 and Q2 from
switching and driving transformer T3. So that eventually the
ATX supply stops "pushing" into the load. There are no crowbar
circuits on the output. The only thing that brings down
the voltage, is the load drawing current from the output
caps.

ATX has nothing to "pull" outputs down. It does not do
push pull regulation. It is a push-only circuit, with
a feedback loop that says "OK, stop pushing now".

If you short a +12V wire to a +5V wire, the +5V output
promptly shoots up to +12V, just like that. The two
Transorbs on the disk drive, cannot handle sustained
abuse, and the +5V Transorb would just burn, until
it could no longer protect, and the drive controller
is ruined. It depends on how quickly Q1/Q2 drive is
removed, how much energy is stored in the +12V output
filter cap, as to how many joules can be used to
destroy the Transorb (when rails are shorted together).
The Transorbs are there to handle "Hot Plug" inductive
kick events, not as a means of defense against
defective power supplies.

Most of the ATX protection is implemented "on the drive side",
not "on the load side".

The only actual "push-pull" regulator in a computer,
is a two amp device running Vtt on the DIMMs. It has
to be push-pull, due to the way terminator currents flow.

*******

You can find discussions about the "bad" ATX supply here.

https://www.badcaps.net/forum/showthread.php?t=9079

The bad "killer" bestec is the ATX-250 12E

The hand drawn schematics show them modifying the +5VSB on
the 12E, so the part that's been removed, must have been
a menace. (Use the "Download Original" button on Postimg
to get the full resolution picture.)

https://i.postimg.cc/vTLcy1yn/Bestec-ATX-250-12-E.png

You'd have to trace further, to find out why an out-of-range
+5VSB as part of the supervision circuit, would cause the
+5V output to be bad. I thought it was the 12E that could
blow hard drives and optical drives and keyboards etc.

*******

You can see a basic crowbar circuit here (uses SCR to clamp
rail to 0V, causes fuse F1 to blow). These would take
a fair amount of space, if every rail needed an SCR,
and then the entry fuse (present in each ATX), a slow-blo,
would need to be mounted in a cartridge format for
easy replacement.

https://www.sunpower-uk.com/glossary...ar-protection/

I don't think doing that is common, and neither is it
a good idea. I built a crowbar once, for a home made power
supply, did a test on it, and the SCR was blown to hell.
(The silicon die stayed inside the SCR hex package, but
the "tink" sound tells you the silicon die was blown
off its substrate.) I never built any more crowbars after
that. I thought I'd done the I squared T or whatever calc
OK, but the only limiting resistor I had was a length of
copper wire. Which apparently wasn't enough.

And you can't feasibly add series pass elements, because
the on-resistance is too high. Imagine a 12V 100A output
with a 50 milliohm series element, say. I squared R
would be 10000*0.050 = 500W of heat in the series
pass element. The series pass element would need to be
better than that, to drop the waste heat level. The
efficiency of the supply would be "the pits".

The economics of power supply design, dictate the solution.
And while there are lots of whacky things you could
implement, they probably wouldn't fit in the cubic inches
of space available.

Most of the time, a failure is within the feedback loop
of the supply, and drive can be removed quickly enough
that the transient... would be survivable. That
might be the premise of operation, and why most of the
time nothing bad happens. It's rail to rail short
circuits that are a bit harder on the loads connected.
and the available energy, is the amount stored in the
output caps (up to 5000uF say). A short inside one of
those crappy SATA power connectors could do it.

Paul

On 6/26/19 12:06 PM, David W. Hodgins wrote:
On Wed, 26 Jun 2019 09:27:25 -0400, philo wrote:

Does any manufacturer have a supply with fully surge-protected OUTPUT?
I assumed they all did.

Not well enough to handle a lightning strike. I had a strike kill the mb,
ps, and two of three hard drives.

The lighting had hit a transformer across the street. Enough power came
through to kill that computer. I've since purchased a ups system. While
it protects against short term power loss, gives time to shut down safely
for longer period losses, and filters out the variations in voltage, etc.,
I haven't had another lightning strike like that one, so don't know if it
is enough to protect from that or not. It also killed all of the
incandescent light bulbs that were on at the time, and tripped all of the
circuit breakers that had any power going through them.

I'd expect the protection in a desktop computer's power supply to protect
from minor variations in voltage, but not much else.

Regards, Dave Hodgins




My machines are on commercial grade UPS' and have survived a direct hit
to the incoming power line.

What concerns me is the OUTPUT side of the PSU

On 6/26/19 12:16 PM, Paul wrote:
philo wrote:
I've repaired thousands of machines and once in a while have seen a
failed power supply take out a motherboard.

Only once though have I seen the hard drives taken out.

It was with a good quality supply and I thought it was just a very odd
fluke.


Last night I talked to someone who had also had it happen ,....so my
question is:


Does any manufacturer have a supply with fully surge-protected OUTPUT?


I assumed they all did.

There is a schematic of a basic ATX supply here.

http://www.pavouk.org/hw/en_atxps.html

That one has overvoltage protection -- it stops Q1 and Q2 from
switching and driving transformer T3. So that eventually the
ATX supply stops "pushing" into the load. There are no crowbar
circuits on the output. The only thing that brings down
the voltage, is the load drawing current from the output
caps.

ATX has nothing to "pull" outputs down. It does not do
push pull regulation. It is a push-only circuit, with
a feedback loop that says "OK, stop pushing now".

If you short a +12V wire to a +5V wire, the +5V output
promptly shoots up to +12V, just like that. The two
Transorbs on the disk drive, cannot handle sustained
abuse, and the +5V Transorb would just burn, until
it could no longer protect, and the drive controller
is ruined. It depends on how quickly Q1/Q2 drive is
removed, how much energy is stored in the +12V output
filter cap, as to how many joules can be used to
destroy the Transorb (when rails are shorted together).
The Transorbs are there to handle "Hot Plug" inductive
kick events, not as a means of defense against
defective power supplies.

Most of the ATX protection is implemented "on the drive side",
not "on the load side".

The only actual "push-pull" regulator in a computer,
is a two amp device running Vtt on the DIMMs. It has
to be push-pull, due to the way terminator currents flow.

*******

You can find discussions about the "bad" ATX supply here.

https://www.badcaps.net/forum/showthread.php?t=9079

Â*Â* The bad "killer" bestec is the ATX-250 12E

The hand drawn schematics show them modifying the +5VSB on
the 12E, so the part that's been removed, must have been
a menace. (Use the "Download Original" button on Postimg
to get the full resolution picture.)

https://i.postimg.cc/vTLcy1yn/Bestec-ATX-250-12-E.png

You'd have to trace further, to find out why an out-of-range
+5VSB as part of the supervision circuit, would cause the
+5V output to be bad. I thought it was the 12E that could
blow hard drives and optical drives and keyboards etc.

*******

You can see a basic crowbar circuit here (uses SCR to clamp
rail to 0V, causes fuse F1 to blow). These would take
a fair amount of space, if every rail needed an SCR,
and then the entry fuse (present in each ATX), a slow-blo,
would need to be mounted in a cartridge format for
easy replacement.

https://www.sunpower-uk.com/glossary...ar-protection/

I don't think doing that is common, and neither is it
a good idea. I built a crowbar once, for a home made power
supply, did a test on it, and the SCR was blown to hell.
(The silicon die stayed inside the SCR hex package, but
the "tink" sound tells you the silicon die was blown
off its substrate.) I never built any more crowbars after
that. I thought I'd done the I squared T or whatever calc
OK, but the only limiting resistor I had was a length of
copper wire. Which apparently wasn't enough.

And you can't feasibly add series pass elements, because
the on-resistance is too high. Imagine a 12V 100A output
with a 50 milliohm series element, say. I squared R
would be 10000*0.050 = 500W of heat in the series
pass element. The series pass element would need to be
better than that, to drop the waste heat level. The
efficiency of the supply would be "the pits".

The economics of power supply design, dictate the solution.
And while there are lots of whacky things you could
implement, they probably wouldn't fit in the cubic inches
of space available.

Most of the time, a failure is within the feedback loop
of the supply, and drive can be removed quickly enough
that the transient... would be survivable. That
might be the premise of operation, and why most of the
time nothing bad happens. It's rail to rail short
circuits that are a bit harder on the loads connected.
and the available energy, is the amount stored in the
output caps (up to 5000uF say). A short inside one of
those crappy SATA power connectors could do it.

Â*Â* Paul



I did not specifically see MOVs on the outputs.

When I was working in industrial electronics I added them to most
everything. I may have to add MOV's to my own equipment if there I can't
find a manufacturer that does so.

On 6/26/2019 9:27 AM, philo wrote:
I've repaired thousands of machines and once in a while have seen a failed
power supply take out a motherboard.

Only once though have I seen the hard drives taken out.

It was with a good quality supply and I thought it was just a very odd fluke.


Last night I talked to someone who had also had it happen ,....so my
question is:


Does any manufacturer have a supply with fully surge-protected OUTPUT?


I assumed they all did.

I, too, have had one PSU misbehave and take out a hard drive but that was a
very long time ago and with a no-name PSU. I learned my lesson after that
and now use nothing but Seasonic supplies, at least in situations where
they make a supply that will fit. Right now the only computers I own that
don't have Seasonic are my Shuttle cubes and they are tied to the
form-specific equipment. Luckily the Shuttle PSUs have proven to be
faultless also.

I don't know of any maker that installs crowbar protection on their
supplies although I believe it would take little more than a high-current
SCR a Zener diode and a few other passive components to work the magic.

On 6/30/19 9:29 AM, John McGaw wrote:
On 6/26/2019 9:27 AM, philo wrote:
I've repaired thousands of machines and once in a while have seen a
failed power supply take out a motherboard.

Only once though have I seen the hard drives taken out.

It was with a good quality supply and I thought it was just a very odd
fluke.


Last night I talked to someone who had also had it happen ,....so my
question is:


Does any manufacturer have a supply with fully surge-protected OUTPUT?


I assumed they all did.

I, too, have had one PSU misbehave and take out a hard drive but that
was a very long time ago and with a no-name PSU. I learned my lesson
after that and now use nothing but Seasonic supplies, at least in
situations where they make a supply that will fit. Right now the only
computers I own that don't have Seasonic are my Shuttle cubes and they
are tied to the form-specific equipment. Luckily the Shuttle PSUs have
proven to be faultless also.

I don't know of any maker that installs crowbar protection on their
supplies although I believe it would take little more than a
high-current SCR a Zener diode and a few other passive components to
work the magic.



All I know is that for industrial use MOV's were everywhere and they worked.

That said, If I try my own modifications I'll do it on a non-critical
machine first.


Will also look into Seasonic PSU's, thanks

On 6/30/2019 7:00 PM, philo wrote:
On 6/30/19 9:29 AM, John McGaw wrote:
On 6/26/2019 9:27 AM, philo wrote:
I've repaired thousands of machines and once in a while have seen a
failed power supply take out a motherboard.

Only once though have I seen the hard drives taken out.

It was with a good quality supply and I thought it was just a very odd
fluke.


Last night I talked to someone who had also had it happen ,....so my
question is:


Does any manufacturer have a supply with fully surge-protected OUTPUT?


I assumed they all did.

I, too, have had one PSU misbehave and take out a hard drive but that was
a very long time ago and with a no-name PSU. I learned my lesson after
that and now use nothing but Seasonic supplies, at least in situations
where they make a supply that will fit. Right now the only computers I
own that don't have Seasonic are my Shuttle cubes and they are tied to
the form-specific equipment. Luckily the Shuttle PSUs have proven to be
faultless also.

I don't know of any maker that installs crowbar protection on their
supplies although I believe it would take little more than a high-current
SCR a Zener diode and a few other passive components to work the magic.



All I know is that for industrial use MOV's were everywhere and they worked.

That said, If I try my own modifications I'll do it on a non-critical
machine first.


Will also look into Seasonic PSU's, thanks

Oh, I've use MOVs for various things but the problem is that they aren't
all that precise. Great at absorbing and dissipating lots of power but the
voltage at which they operate are vague at best. I've used bushels of them
protecting broadcast and computer equipment from line transients but I'd be
hard pressed to set them up to protect a 12V circuit from going above 13.5V
where damage to a hard drive might be expected to begin. A glance at some
spec sheets suggests that using a 12V MOV the clamping voltage might be
40+. But if you decide to give it a shot and make it work well, please let
up know.

On 7/1/19 9:59 AM, John McGaw wrote:
On 6/30/2019 7:00 PM, philo wrote:
On 6/30/19 9:29 AM, John McGaw wrote:
On 6/26/2019 9:27 AM, philo wrote:
I've repaired thousands of machines and once in a while have seen a
failed power supply take out a motherboard.

Only once though have I seen the hard drives taken out.

It was with a good quality supply and I thought it was just a very
odd fluke.


Last night I talked to someone who had also had it happen ,....so my
question is:


Does any manufacturer have a supply with fully surge-protected OUTPUT?


I assumed they all did.

I, too, have had one PSU misbehave and take out a hard drive but that
was a very long time ago and with a no-name PSU. I learned my lesson
after that and now use nothing but Seasonic supplies, at least in
situations where they make a supply that will fit. Right now the only
computers I own that don't have Seasonic are my Shuttle cubes and
they are tied to the form-specific equipment. Luckily the Shuttle
PSUs have proven to be faultless also.

I don't know of any maker that installs crowbar protection on their
supplies although I believe it would take little more than a
high-current SCR a Zener diode and a few other passive components to
work the magic.



All I know is that for industrial use MOV's were everywhere and they
worked.

That said, If I try my own modifications I'll do it on a non-critical
machine first.


Will also look into Seasonic PSU's, thanks

Oh, I've use MOVs for various things but the problem is that they aren't
all that precise. Great at absorbing and dissipating lots of power but
the voltage at which they operate are vague at best. I've used bushels
of them protecting broadcast and computer equipment from line transients
but I'd be hard pressed to set them up to protect a 12V circuit from
going above 13.5V where damage to a hard drive might be expected to
begin. A glance at some spec sheets suggests that using a 12V MOV the
clamping voltage might be 40+. But if you decide to give it a shot and
make it work well, please let up know.




Well, if I install MOV's and never have a HD burn out again it still
does not prove they did the trick.


I have a few other ideas though.


The person I know who lost two drives had a RAID 1 (mirrored) so he
thought he was safe.

Now I see that one possible way to build a reliable machine would be to
have each drive powered by a completely separate supply and probably
from a different manufacturer.


That said, it's been my experience in life that no matter what you plan
for, something else is going to happen!

Maybe I'll just continue doing backups because to reinstall the OS is
not a big deal...all that's important it the data

On 7/1/2019 11:20 AM, philo wrote:
On 7/1/19 9:59 AM, John McGaw wrote:
On 6/30/2019 7:00 PM, philo wrote:
On 6/30/19 9:29 AM, John McGaw wrote:
On 6/26/2019 9:27 AM, philo wrote:
I've repaired thousands of machines and once in a while have seen a
failed power supply take out a motherboard.

Only once though have I seen the hard drives taken out.

It was with a good quality supply and I thought it was just a very odd
fluke.


Last night I talked to someone who had also had it happen ,....so my
question is:


Does any manufacturer have a supply with fully surge-protected OUTPUT?


I assumed they all did.

I, too, have had one PSU misbehave and take out a hard drive but that
was a very long time ago and with a no-name PSU. I learned my lesson
after that and now use nothing but Seasonic supplies, at least in
situations where they make a supply that will fit. Right now the only
computers I own that don't have Seasonic are my Shuttle cubes and they
are tied to the form-specific equipment. Luckily the Shuttle PSUs have
proven to be faultless also.

I don't know of any maker that installs crowbar protection on their
supplies although I believe it would take little more than a
high-current SCR a Zener diode and a few other passive components to
work the magic.



All I know is that for industrial use MOV's were everywhere and they
worked.

That said, If I try my own modifications I'll do it on a non-critical
machine first.


Will also look into Seasonic PSU's, thanks

Oh, I've use MOVs for various things but the problem is that they aren't
all that precise. Great at absorbing and dissipating lots of power but
the voltage at which they operate are vague at best. I've used bushels of
them protecting broadcast and computer equipment from line transients but
I'd be hard pressed to set them up to protect a 12V circuit from going
above 13.5V where damage to a hard drive might be expected to begin. A
glance at some spec sheets suggests that using a 12V MOV the clamping
voltage might be 40+. But if you decide to give it a shot and make it
work well, please let up know.




Well, if I install MOV's and never have a HD burn out again it still does
not prove they did the trick.


I have a few other ideas though.


The person I know who lost two drives had a RAID 1 (mirrored) so he thought
he was safe.

Now I see that one possible way to build a reliable machine would be to
have each drive powered by a completely separate supply and probably from a
different manufacturer.


That said, it's been my experience in life that no matter what you plan
for, something else is going to happen!

Maybe I'll just continue doing backups because to reinstall the OS is not a
big deal...all that's important it the data

There is no substitute for backups. No matter what. I am quite paranoid
about protecting my primary machine. As I write this it is doing its
monthly backup which will go into the bank's vault this afternoon -- there
are three portable drives cycling through these backups. Every evening it
does a full backup to my elderly WHS and at 1AM it did a backup to one of
my redundant Drobo NAS units. Oh, and as the mood strikes me I do a system
disk image to a series of portable SSD units that are kept in a media safe
here at home in case I need to restore a bootable image. I have been burned
too many times by seemingly random glitches. This level of backup would be
overkill for most people but I believe that any user who doesn't have at
least two levels of backup, one of them offsite but under his/her direct
control, is a fool and probably deserves whatever comes their way.