Cheap/generic PSUs - any good? (was: Low power socket A)

Michael Brown" <see@signature.below> wrote:
>
> kony wrote:
>> On Sat, 18 Sep 2004 07:34:08 GMT, Wes Newell
>> <w.newell@TAKEOUTverizon.net> wrote:
> [...]
>>>> As I mentioned previously, if you have a specific PSU you
>>>> can, with confidence, recommend based on it running a very
>>>> similar system (to the extent that power distribution among
>>>> the different rails is also similar), for over a year, that
>>>> might be relevent... at least it would suggest same
>>>> make/model might suffice, for a year. Success with same or
>>>> different generics running lower-powered old systems is not
>>>> relevant.
>>>
>>> Well, this would cover about every PSU I've ever bought.:-)
>>
>> ... and yet generic PSU cause problems quite often, it just
>> seems that you have a golden touch with them.
>
> For what it's worth, everyone I know except one has generic
> PSUs in their systems (myself included). This coveres probably
> somewhere in the range of 30-40 systems, ranging from P4 1.6's
> to A64 3200's and dual-MP2800 systems. The only one I've known
> to fail under normal circumstances is when a friend of mine
> plugged an (overclocked) XP2000 Palomino into an ancient (and
> known to blow under high loads) 230W PSU I'd given him to power
> an old Pentium-1 class machine. Pop and smoke, but nothing
> damaged.


(1) If there is no load applied to a PC's power supply then after a few
seconds it burns up unless it has protective circuitry. I had thought that
cheaper/generic PC PSUs tended to lack this protective circuitry.

(2) I had also thought that the cheaper/generic PC PSU's were more likely
to permit a surge of current through the motherboard if and when the PSU
failed. If I understand this correctly then the motherboard could also get
destroyed.

Are these two dangers no longer a problem with cheap/generic PSUs?






[crossposted to electronics & PC builders groups]

One other problem is cheap PSU's, is that when you load down one of the
rails (ie the 12v rail) that it will affect the other voltage rails. In the
goog PSU's, one rail does not affect the other. In my opinion, you get what
you pay for. If you buy $2,000.00 plus of computer, and then throw in a
$30.00 PSU, you are asking for trouble. If you bought a Ferrari F50, would
you put regular unleaded in it?? or maybe an engine from chevette??




"Mark: csiphs" <CANT_RECEIVE_MAIL@com.invalid> wrote in message
news:956BCC9C61EED3A75@130.133.1.4...
> Michael Brown" <see@signature.below> wrote:
>>
>> kony wrote:
>>> On Sat, 18 Sep 2004 07:34:08 GMT, Wes Newell
>>> <w.newell@TAKEOUTverizon.net> wrote:
>> [...]
>>>>> As I mentioned previously, if you have a specific PSU you
>>>>> can, with confidence, recommend based on it running a very
>>>>> similar system (to the extent that power distribution among
>>>>> the different rails is also similar), for over a year, that
>>>>> might be relevent... at least it would suggest same
>>>>> make/model might suffice, for a year. Success with same or
>>>>> different generics running lower-powered old systems is not
>>>>> relevant.
>>>>
>>>> Well, this would cover about every PSU I've ever bought.:-)
>>>
>>> ... and yet generic PSU cause problems quite often, it just
>>> seems that you have a golden touch with them.
>>
>> For what it's worth, everyone I know except one has generic
>> PSUs in their systems (myself included). This coveres probably
>> somewhere in the range of 30-40 systems, ranging from P4 1.6's
>> to A64 3200's and dual-MP2800 systems. The only one I've known
>> to fail under normal circumstances is when a friend of mine
>> plugged an (overclocked) XP2000 Palomino into an ancient (and
>> known to blow under high loads) 230W PSU I'd given him to power
>> an old Pentium-1 class machine. Pop and smoke, but nothing
>> damaged.
>
>
> (1) If there is no load applied to a PC's power supply then after a few
> seconds it burns up unless it has protective circuitry. I had thought
> that
> cheaper/generic PC PSUs tended to lack this protective circuitry.
>
> (2) I had also thought that the cheaper/generic PC PSU's were more likely
> to permit a surge of current through the motherboard if and when the PSU
> failed. If I understand this correctly then the motherboard could also
> get
> destroyed.
>
> Are these two dangers no longer a problem with cheap/generic PSUs?
>
>
>
>
>
>
> [crossposted to electronics & PC builders groups]

Fun when the fan stops. Had it happen.


--
Ed Light

Smiley :-/
MS Smiley :-\

Send spam to the FTC at
uce@ftc.gov
Thanks, robots.

"Ed Light" wrote:
> Fun when the fan stops. Had it happen.

Yep, also fun when capacitors blow and take out the motherboard - had that happen too.

Jon

Mark: csiphs wrote:
> Michael Brown" <see@signature.below> wrote:
>
>>kony wrote:
>>
>>>On Sat, 18 Sep 2004 07:34:08 GMT, Wes Newell
>>><w.newell@TAKEOUTverizon.net> wrote:
>>
>>[...]
>>
>>>>>As I mentioned previously, if you have a specific PSU you
>>>>>can, with confidence, recommend based on it running a very
>>>>>similar system (to the extent that power distribution among
>>>>>the different rails is also similar), for over a year, that
>>>>>might be relevent... at least it would suggest same
>>>>>make/model might suffice, for a year. Success with same or
>>>>>different generics running lower-powered old systems is not
>>>>>relevant.
>>>>
>>>>Well, this would cover about every PSU I've ever bought.:-)
>>>
>>>... and yet generic PSU cause problems quite often, it just
>>>seems that you have a golden touch with them.
>>
>>For what it's worth, everyone I know except one has generic
>>PSUs in their systems (myself included). This coveres probably
>>somewhere in the range of 30-40 systems, ranging from P4 1.6's
>>to A64 3200's and dual-MP2800 systems. The only one I've known
>>to fail under normal circumstances is when a friend of mine
>>plugged an (overclocked) XP2000 Palomino into an ancient (and
>>known to blow under high loads) 230W PSU I'd given him to power
>>an old Pentium-1 class machine. Pop and smoke, but nothing
>>damaged.
>
>
>
> (1) If there is no load applied to a PC's power supply then after a few
> seconds it burns up unless it has protective circuitry. I had thought that
> cheaper/generic PC PSUs tended to lack this protective circuitry.

Sounds like an urban myth.

Without a load the PSU can't regulate (an inherent characteristic of
switching power supplies) but, while I can't say I've seen 'every' power
supply out there, I've never seen one 'burn up' from being unloaded.

>
> (2) I had also thought that the cheaper/generic PC PSU's were more likely
> to permit a surge of current through the motherboard if and when the PSU
> failed. If I understand this correctly then the motherboard could also get
> destroyed.

There are two basic types of output 'protection'. One is over-current
protection (OCP). That is to protect the power supply from a fault external
to the PSU pulling more current than the PSU can provide and wouldn't
protect the motherboard since, if it's pulling fault current then, there's
already something wrong.

I's be surprised if there are many, if any, PSUs that don't have OCP
because that's built into the switching regulator ICs that everyone pretty
much has to use and, btw, this is what causes the symptom of the front
panel power switch won't turn it back on after the 'no boot' with 'the fans
immediately stopped spinning' power on fault. The OCP needs to be reset by
turning off the PSU with the rear PSU power switch, or unplugging it, for
some brief period of time, say 10 seconds, so the internal caps can bleed off.

The other is over-voltage protection (OVP). That circuit should clamp the
output to a 'safe' level if something in the PSU fails causing it to put
out excessive voltage. That would only matter if the fault specifically
caused an over-voltage rather than, say, the outputs going dead to begin
with. It's effectiveness is complicated by how fast it responds and how it
controls the voltage.



> Are these two dangers no longer a problem with cheap/generic PSUs?
>
>
>
>
>
>
> [crossposted to electronics & PC builders groups]

In article <10l19fpsc3h0p2d@corp.supernews.com>,
David Maynard <dNOTmayn@ev1.net> wrote:

>> (2) I had also thought that the cheaper/generic PC PSU's were more likely
>> to permit a surge of current through the motherboard if and when the PSU
>> failed. If I understand this correctly then the motherboard could also get
>> destroyed.
>
>There are two basic types of output 'protection'. One is over-current
>protection (OCP). That is to protect the power supply from a fault external
>to the PSU pulling more current than the PSU can provide and wouldn't
>protect the motherboard since, if it's pulling fault current then, there's
>already something wrong.

I've read one report which indicated that some cheaper/generic PC PSUs
do seem to be skimping, on the input (AC mains) side of things. These
cheap supplies have only a limited amount of RF filtering and
protective circuitry on the mains side - just enough to keep them from
feeding unacceptable (illegal) amounts of RF hash back into the mains.
They have less (often little or no) protection against high-voltage
spikes, inductive kickback, and mains-born RF noise. As a result,
they're somewhat more likely to suffer damage if there's a significant
high-voltage spike/surge on your mains (as may happen at the start of
end of a power brownout or outage).

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

40 cars run stop signs and have never killed anyone. That
proves stopping is not necessary? Such reasoning without
consulting underlying facts and concepts is called junk
science reasoning. Same junk science reasoning here proves
all that essential power supply circuitry is not required.

All power supplies even 30 years ago required over voltage
and over current protection. As noted by another, some
functions are even provided in power supply controller chips.
Is the function enabled? Only way a consumer can say yes is
if the power supply claims, in writing, that such necessary
functions are provided. If not in writing, then the less than
1% who do such analysis cannot and will not tell others of
missing functions. If power supply does not claim to contain
such functions, then assume essential functions do not exist.

Consumers sometimes suffer failures due to inferior power
supplies. Then they blame failures on 'things that must exist
because they cannot be seen'. Ie power surges. No wonder
some can claim they don't need no stink'in internal
protection. The motherboard caused all his problems. He just
knows.

Switching power supplies can or cannot be operated with no
load. A function defined in power supply manufacturer data
sheets. However a no load condition never damages any
minimally acceptable power supply.

AC mains surges do not pass through switching power
supplies. AC mains first gets filtered. Then gets converted
to 300+ volt DC - more filtering. Then get converted to high
frequency AC. Then passes through an isolation transformer.
Then get converted to DC again. Then gets filtered again.
Power surges on AC mains will pass through all this? Of
course not. Instead destructive surges use other paths that
completely bypass the power supply.

It is very profitable to dump inferior power supplies. Some
even use junk science reasoning to *prove* they know better
than engineers and 30+ years of experience.

Mark: csiphs wrote:
> (1) If there is no load applied to a PC's power supply then
> after a few seconds it burns up unless it has protective
> circuitry. I had thought that cheaper/generic PC PSUs tended
> to lack this protective circuitry.
>
> (2) I had also thought that the cheaper/generic PC PSU's were
> more likely to permit a surge of current through the
> motherboard if and when the PSU failed. If I understand this
> correctly then the motherboard could also get destroyed.
>
> Are these two dangers no longer a problem with cheap/generic PSUs?
>
> [crossposted to electronics & PC builders groups]

Dave Platt wrote:

> In article <10l19fpsc3h0p2d@corp.supernews.com>,
> David Maynard <dNOTmayn@ev1.net> wrote:
>
>
>>>(2) I had also thought that the cheaper/generic PC PSU's were more likely
>>>to permit a surge of current through the motherboard if and when the PSU
>>>failed. If I understand this correctly then the motherboard could also get
>>>destroyed.
>>
>>There are two basic types of output 'protection'. One is over-current
>>protection (OCP). That is to protect the power supply from a fault external
>>to the PSU pulling more current than the PSU can provide and wouldn't
>>protect the motherboard since, if it's pulling fault current then, there's
>>already something wrong.
>
>
> I've read one report which indicated that some cheaper/generic PC PSUs
> do seem to be skimping, on the input (AC mains) side of things. These
> cheap supplies have only a limited amount of RF filtering and
> protective circuitry on the mains side - just enough to keep them from
> feeding unacceptable (illegal) amounts of RF hash back into the mains.
> They have less (often little or no) protection against high-voltage
> spikes, inductive kickback, and mains-born RF noise. As a result,
> they're somewhat more likely to suffer damage if there's a significant
> high-voltage spike/surge on your mains (as may happen at the start of
> end of a power brownout or outage).
>

Yes, that's the more likely place for 'cost savings' in super el-cheapo
PSUs because it takes 'extra', or better, parts to include it.

"Mark: csiphs" <CANT_RECEIVE_MAIL@com.invalid> wrote in message
news:956BCC9C61EED3A75@130.133.1.4...
> Michael Brown" <see@signature.below> wrote:

[snip]

> (1) If there is no load applied to a PC's power supply then after a
few
> seconds it burns up unless it has protective circuitry. I had thought
that
> cheaper/generic PC PSUs tended to lack this protective circuitry.

Of the many cheapo generic AT SMPSes that I've worked on, I cannot
remember ever seeing one without an OVP circuit. This usually quickly
shuts down the PS as soon as the voltage rises over the protection
point, around 5.5VDC.

> (2) I had also thought that the cheaper/generic PC PSU's were more
likely
> to permit a surge of current through the motherboard if and when the
PSU
> failed. If I understand this correctly then the motherboard could
also get
> destroyed.

> Are these two dangers no longer a problem with cheap/generic PSUs?

No longer?? They have never been a problem, AFAIK.

> [crossposted to electronics & PC builders groups]

>
> (1) If there is no load applied to a PC's power supply then after a few
> seconds it burns up unless it has protective circuitry. I had thought
that
> cheaper/generic PC PSUs tended to lack this protective circuitry.


I've never seen one that did that, and I've worked with a lot of power
supplies.


>
> (2) I had also thought that the cheaper/generic PC PSU's were more likely
> to permit a surge of current through the motherboard if and when the PSU
> failed. If I understand this correctly then the motherboard could also
get
> destroyed.

That's entirely possible, I've seen it happen twice, don't know how cheap
the PSU's were.

> Are these two dangers no longer a problem with cheap/generic PSUs?

Whether they are or not, there's plenty of reasons not to get the cheapest
ones you can find. As with audio equipment, there's plenty of stuff out
there with ridiculous wattage ratings on it, but you'll pay accordingly for
a *real* 300W output.