Shortest period to switch off electronic equipent for before

[pamela]

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

 

[Rheilly Phoull]

On 8/04/2017 5:33 PM, pamela wrote:

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

You might want to regulate your relatives when they are in YOUR HOME.
As you say some things need a few seconds to reset.

 

[Davey]

On Sat, 08 Apr 2017 10:33:44 +0100
pamela <invalid@nospam.com> wrote:

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

My Humax HDR Fox T2 says to wait until you hear the HDD wind down
before turning it on again. Otherwise, I generally try to wait for 30
secs. as a rule of thumb, although I'm not always that patient. Not
that I have to reset stuff much anyway.

If they're in your home, then visitors work to your rules!

--
Davey.

 

[David Woolley]

On 08/04/17 10:33, pamela wrote:

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

There are two issues here:

1) allowing long enough for a reset to be reliable;

2) ensuring it is safe to power down before doing so.

On the second point, PVRs, in particular, do not seem to be designed to
be really safe to power down at any time, as there is no way of putting
them into a soft power down state. You have to make sure that there are
no recordings scheduled and put them into standby. On my Humax, you
then need to wait until the red light dims

Otherwise, you will be relying on the consumer user defences built into
the disk drives ensure that the current write completes and the heads
park, and also to recover any logical damage to the filesystem. Even
PC's are quite good at this these days, and should never be given a hard
power down until a soft power down has completed, unless they have
completely locked up and there is no reset button.

On the first point, it depends on the design of the electronics as to
how long it takes for all capacitors to discharge sufficiently to put
them into a clearly off state. Remember that some devices will detect a
warm start by reading RAM, and maximum retention times, without
refreshes, are not characterised for dynamic RAM, only minimum ones.

Also the time constants associated with some faults that require resets
can be hours.

Where a hard power cycle is needed, I would probably go for about 30
seconds for the first attempt, and then overnight, if the first attempt
doesn't succeed.

Of course, you should not need to reset the device this way at all,
unless there is a fault, so it is probably something that you should not
allow visitors to do at all.

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

 

[Davey]

On Sat, 8 Apr 2017 12:03:14 +0100
David Woolley <david@ex.djwhome.demon.invalid> wrote:

Of course, you should not need to reset the device this way at all,
unless there is a fault,

A few days ago, for the first time that I have ever seen, my Humax
refused to respond when I tried to turn it on. Neither the remote
control nor the big button would make it work. I turned it off with the
switch on the back panel, waited some time, probably less than 30
seconds, and then turned it on again. Since then, it's worked fine. The
log showed nothing of any use, so I have no idea what the problem was.
The unit is now about 4 years old, and was a refurbished unit when I got
it, so I have had my money's worth if it failed at any time.

--
Davey.

 

[pamela]

On 12:11 8 Apr 2017, Davey wrote:

On Sat, 8 Apr 2017 12:03:14 +0100
David Woolley <david@ex.djwhome.demon.invalid> wrote:

Of course, you should not need to reset the device this way at
all, unless there is a fault,

A few days ago, for the first time that I have ever seen, my
Humax refused to respond when I tried to turn it on. Neither the
remote control nor the big button would make it work. I turned
it off with the switch on the back panel, waited some time,
probably less than 30 seconds, and then turned it on again.
Since then, it's worked fine. The log showed nothing of any use,
so I have no idea what the problem was. The unit is now about 4
years old, and was a refurbished unit when I got it, so I have
had my money's worth if it failed at any time.

To my young relative 30 seconds is like an eternity. If I advised
him to wait 30 seconds before turning equipment back on again, he
would never manage it.

However his OFF-ON is so quick that it makes me think on some
occassions he could create a power surge.

 

[MJC]

In article <ocafrr$ehp$1@dont-email.me>, david@ex.djwhome.demon.invalid
says...

On the second point, PVRs, in particular, do not seem to be designed
to
be really safe to power down at any time, as there is no way of putting
them into a soft power down state. You have to make sure that there are
no recordings scheduled and put them into standby. On my Humax, you
then need to wait until the red light dims

My Humax (old 9200T) will record even when in standby. On the other
hand, it sometimes gets stuck and has to be powered down to reset it.
And I give it several seconds, but not as many as 30!

Mike.

 

[Benderthe.evilrobot]

"pamela" <invalid@nospam.com> wrote in message
news:XnsA7516B728743CD4AM2@81.171.92.183...

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

You can't just lump everything into the same bracket - a lot of people just
turn the TV off "cold turkey", its a lot better than leaving it unattended
on standby.

Anything with a hard drive can trash a file if you power down in the middle
of a write operation.

Some designs of SMPSU can go bang if you switch back on before the reservoir
caps discharge and those with inrush surge limiting have a thermal recovery
time for no protection - but it just stresses the components a little more
than usual. Most user manuals seem more or less unanimous for about 30s.


---
This email has been checked for viruses by AVG.
http://www.avg.com

 

On Saturday, April 8, 2017 at 3:16:40 PM UTC-4, Benderthe.evilrobot wrote:

"pamela" <invalid@nospam.com> wrote in message
news:XnsA7516B728743CD4AM2@81.171.92.183...
As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

You can't just lump everything into the same bracket - a lot of people just
turn the TV off "cold turkey", its a lot better than leaving it unattended
on standby.

Anything with a hard drive can trash a file if you power down in the middle
of a write operation.

Some designs of SMPSU can go bang if you switch back on before the reservoir
caps discharge and those with inrush surge limiting have a thermal recovery
time for no protection - but it just stresses the components a little more
than usual. Most user manuals seem more or less unanimous for about 30s.


---
This email has been checked for viruses by AVG.
http://www.avg.com

Most of this is dependent on the carefulness of the design. If power loss or brownouts is given consideration by the designer, none of this is a problem.

 

On Sat, 8 Apr 2017 20:17:20 +0100, "Benderthe.evilrobot"
<Benderthe.evilrobot@virginmedia.com> wrote:

"pamela" <invalid@nospam.com> wrote in message
news:XnsA7516B728743CD4AM2@81.171.92.183...
As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

You can't just lump everything into the same bracket - a lot of people just
turn the TV off "cold turkey", its a lot better than leaving it unattended
on standby.

Anything with a hard drive can trash a file if you power down in the middle
of a write operation.

Some designs of SMPSU can go bang if you switch back on before the reservoir
caps discharge and those with inrush surge limiting have a thermal recovery
time for no protection - but it just stresses the components a little more
than usual. Most user manuals seem more or less unanimous for about 30s.


---

I have a small low powered solid state stereo receiver. I noticed that
things is always using power when it's turned off. A few weeks ago,
while this receiver was OFF, I removed the speaker wires to test another
amp. I then unplugged the receiver. Last week I put the speaker wires
back on that receiver (it was still unplugged). There was a loud pop on
each channel when I put the wires on it. (That was around 16 days
later). Those caps must hold power for a real long time..... (There is
no battery of any sort in this thing).

Another thing, I have an external 56K modem that I use to connect (on
dialup). Once and awhile if I shut off connection, later on, I have
trouble connecting to the internet. I found that if I just shut the
power off to that modem, it seems to reset it and thn it connects fine.
BUT. I have to shut it off for about 30 seconds. Just ON-OFF dont work.
I assume the caps need to discharge to do the reset....

 

On Sat, 8 Apr 2017 20:17:20 +0100, "Benderthe.evilrobot"
<Benderthe.evilrobot@virginmedia.com> wrote:

"pamela" <invalid@nospam.com> wrote in message
news:XnsA7516B728743CD4AM2@81.171.92.183...
As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

You can't just lump everything into the same bracket - a lot of people just
turn the TV off "cold turkey", its a lot better than leaving it unattended
on standby.

There is absolutly nothing wrong with "standby".

Anything with a hard drive can trash a file if you power down in the middle
of a write operation.

Nonsense. There are many ways to design a device that will survive a
power failure during disk write. A bit of reserve power is probably
the best solution but a JFS works, too.

Some designs of SMPSU can go bang if you switch back on before the reservoir
caps discharge and those with inrush surge limiting have a thermal recovery
time for no protection - but it just stresses the components a little more
than usual. Most user manuals seem more or less unanimous for about 30s.

Only if it's designed by a moron.

 

[alan_m]

On 08/04/2017 10:33, pamela wrote:

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

Twenty years ago 5 seconds may have caused a problem due to the
possibility of surges due to mains input filters.

Often if the switch off is to cold boot crashed software then the
internal PSU voltages have to decay. My rule of thumb is 30 seconds
after any front panel LED has gone out.

--
mailto: news {at} admac {dot] myzen {dot} co {dot} uk

 

[David Woolley]

On 08/04/17 17:15, MJC wrote:
> My Humax (old 9200T) will record even when in standby

That's why I said you must make sure there are no recordings scheduled!

 

[Brian Gaff]

In my view all devices should have a little pin hole switch that does this
for you.
It really depends on the device I think. Things like my Smart talk freeview
box almost instantaneous resets are OK if done via the little plug from the
psu on the back, but if you do it from the mains it needs a little longer as
I suspect the wall wart has some capacitors in it.

Phones are awhole other ball of nuts.
Some seem to remember crashes indefinitely. there is one which is not out
of production where the software crashes and stops the voice from working at
all, even if you take the battery out.
Sadly as nobody has the gear to reblow the software any more its a brick.
Brian

--
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please!
"pamela" <invalid@nospam.com> wrote in message
news:XnsA7516B728743CD4AM2@81.171.92.183...

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

 

[Brian Gaff]

Not many people understand computer shut down via the button either If
software has locked up or is doing odd things, then a short tap on the power
button, ie NOT the reset is normally the way to get a good shutdown. If that
fails, then hold in the power button, NOT the reset button as this normally
protects the hard drive from corruption. all these folks wo either press
reset or worse, just pull the plug out deserve the reinstall they
evenntually end up having to do.
Brian
Of course if there is a power cut this can happen anyway, and I've often
thought of putting in an uninteruptable supply to allow proper shut down.
they are not that expensive these days, and laptops of course have one built
in.
Brian

--
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please!
"Davey" <davey@example.invalid> wrote in message
newscadad$j1m$4@n102.xanadu-bbs.net...

On Sat, 08 Apr 2017 10:33:44 +0100
pamela <invalid@nospam.com> wrote:

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

My Humax HDR Fox T2 says to wait until you hear the HDD wind down
before turning it on again. Otherwise, I generally try to wait for 30
secs. as a rule of thumb, although I'm not always that patient. Not
that I have to reset stuff much anyway.

If they're in your home, then visitors work to your rules!

--
Davey.

 

[NY]

<krw@notreal.com> wrote in message
news:sg5jeclipaol2ejgd0tuivrostvvad23bt@4ax.com...

You can't just lump everything into the same bracket - a lot of people
just
turn the TV off "cold turkey", its a lot better than leaving it unattended
on standby.

There is absolutly nothing wrong with "standby".

Anything with a hard drive can trash a file if you power down in the
middle
of a write operation.

I suppose anything with disk-like storage (including flash drives) can be
trashed if the power goes off during a write, though the time during which
the files is in an inconsistent state between data sectors and sector map
may be less with solid state than a mechanical rotating disk.

Nonsense. There are many ways to design a device that will survive a
power failure during disk write. A bit of reserve power is probably
the best solution but a JFS works, too.

It depends what filesystem they use. NTFS is pretty robust but it requires a
licence to be paid to the inventors which is why a lot of PVRs use/read only
FAT/FAT32. If they are Linux-based they will be able to use filesystems
which are more robust (I'm not very clued up on Linux).

But I'd say that a design which trashes the file that is being written to or
the whole filesystem when the power goes off (eg due to a power-cut, which
is not totally unexpected) is a bad design: you need some form of resilience
in terms of battery-backed supply until the file write is complete and
consistent.

I use my Windows 7 PC as a PVR (either Windows Media Centre or NextPVR) and
I've occasionally had power cuts during recording. I've never yet lost the
recording that was being made or the filesystem of the recording HDD (NTFS).
OK, Windows may do a chkdsk repair after the PC reboots, but it seems to
sort itself out.

A UPS would be useful for graceful shutting down during power cuts, but it
might be more trouble that it's worth. At present my BIOS is set to reboot
the PC automatically after the power is restored. If the UPS keeps the power
up and initiates a graceful shutdown, the PC may not boot back up once the
power comes back.

My wife bought a 3kVA UPS with her big Dell PC about 10 years ago. We didn't
get round to setting up the UPS for a couple of years. By the time we did
(and after the warranty had expired, inevitably) we found that it had
virtually no battery capacity: the battery monitoring software (monitored by
USB connection) showed the battery accepting charge and gradually charging
up and eventually showing as fully charged, but as soon as the mains was
removed, the battery discharged within about 10 seconds with a nominal 40 W
lightbulb as the load. Utterly useless, and it wasn't even worth buying a
replacement battery for it because the fault may have been in the charging
circuit rather than the battery itself. APC didn't want to know when we
asked what a repair might cost, so it went in the skip - a waste of money as
it was never even used.

Moral of the story: always try any new hardware during the warranty period!

 

[Look165]

Generally, the off/on if too short implies caps (generally somme 100ľF)
not to discharge totally and if on again during this state, the result
is unpredictable.

Thje more the device uses power, the less this time is needed.

Today, it seems that 10-15 s are enough.

For a modem (ADSL or cable) it's OK.

For a LCD or plasma TV too.

To be secure, count on 20s.



pamela a écrit :

As a rule of thumb, what's the shortest period to switch off
electronic equipment for a reset before switching on?

I mean equipment like televisions, PVR, satellite or cable boxes,
PCs, cordless phones, clock radios, etc.

My teenage relative reset our Humax PVR by switching it off and
almost INSTANTLY switched it on again. I told him to be patient
but how long should he wait for in general?

Twenty years ago 5 seconds would have been enough but nowadays some
electronic devices (like my Samsung tv) shows its power LED for 10 or
20 seconds after the mains is disconnected. Also hard drives in
Playstations and PVRs will spin on. Telling impatient kids to go and
make a cup of coffee isn't going to work.

 

On Sun, 9 Apr 2017 12:21:16 +0100, "NY" <me@privacy.net> wrote:

krw@notreal.com> wrote in message
news:sg5jeclipaol2ejgd0tuivrostvvad23bt@4ax.com...
You can't just lump everything into the same bracket - a lot of people
just
turn the TV off "cold turkey", its a lot better than leaving it unattended
on standby.

There is absolutly nothing wrong with "standby".

Anything with a hard drive can trash a file if you power down in the
middle
of a write operation.

I suppose anything with disk-like storage (including flash drives) can be
trashed if the power goes off during a write, though the time during which
the files is in an inconsistent state between data sectors and sector map
may be less with solid state than a mechanical rotating disk.

Nonsense. There are many ways to design a device that will survive a
power failure during disk write. A bit of reserve power is probably
the best solution but a JFS works, too.

It depends what filesystem they use. NTFS is pretty robust but it requires a
licence to be paid to the inventors which is why a lot of PVRs use/read only
FAT/FAT32. If they are Linux-based they will be able to use filesystems
which are more robust (I'm not very clued up on Linux).

That's an economics decision. There is nothing cast in jello that
says they have to cheap out, or even use an existing FS. JFS
techniques are well known. Even if they do want to use a vulnerable
FS, a proper power system design can guarantee a safe shut down.

But I'd say that a design which trashes the file that is being written to or
the whole filesystem when the power goes off (eg due to a power-cut, which
is not totally unexpected) is a bad design: you need some form of resilience
in terms of battery-backed supply until the file write is complete and
consistent.

Exactly so. This is common with flash-based systems. The power
system has to guarantee at least the current block has been written.

I use my Windows 7 PC as a PVR (either Windows Media Centre or NextPVR) and
I've occasionally had power cuts during recording. I've never yet lost the
recording that was being made or the filesystem of the recording HDD (NTFS).
OK, Windows may do a chkdsk repair after the PC reboots, but it seems to
sort itself out.

NTFS?

A UPS would be useful for graceful shutting down during power cuts, but it
might be more trouble that it's worth. At present my BIOS is set to reboot
the PC automatically after the power is restored. If the UPS keeps the power
up and initiates a graceful shutdown, the PC may not boot back up once the
power comes back.

My wife bought a 3kVA UPS with her big Dell PC about 10 years ago. We didn't
get round to setting up the UPS for a couple of years. By the time we did
(and after the warranty had expired, inevitably) we found that it had
virtually no battery capacity: the battery monitoring software (monitored by
USB connection) showed the battery accepting charge and gradually charging
up and eventually showing as fully charged, but as soon as the mains was
removed, the battery discharged within about 10 seconds with a nominal 40 W
lightbulb as the load. Utterly useless, and it wasn't even worth buying a
replacement battery for it because the fault may have been in the charging
circuit rather than the battery itself. APC didn't want to know when we
asked what a repair might cost, so it went in the skip - a waste of money as
it was never even used.

Always test your emergency system. When I was in IBM, they tested the
emergency generators once a month. I have no idea why they had such
in the building I was in (just offices and a few labs at that time)
but they were there, so the were tested.

It's a really good idea to test your system backups from time to time,
too. You may find the restore doesn't work. :-(

Moral of the story: always try any new hardware during the warranty period!

Anything that's important has to be tested.

 

[David Woolley]

On 09/04/17 10:01, Brian Gaff wrote:

If that
fails, then hold in the power button, NOT the reset button as this normally
protects the hard drive from corruption.

As I understand it, a long press is handled by the hardware and forces a
dirty shutdown. If it were handled by the firmware, it could be
difficult to shut down a battery powered device which had locked up.
RESET should be more gentle than a long press.

Typically, power supplies will not have decayed before any sector write
in progress has completed and disks should park. However, you are
basically relying on fault recovery mechanisms to protect the physical
media, and the low level formatting.

Journalling file systems may protect the basic file structure, but data
buffered in user space, and write back caches (OS and device) will not
get written and very few application designers will have designed them
to be completely safe against partially written files.

Consumer devices have to be tolerant of such abuses, but whenever you
start relying on fault recovery mechanisms, for normal operation, you
are on dangerous ground.

 

[NY]

<krw@notreal.com> wrote in message
news:g0akec5be84fpoh2a0dukvh2613de8i570@4ax.com...

On Sun, 9 Apr 2017 12:21:16 +0100, "NY" <me@privacy.net> wrote:
My wife bought a 3kVA UPS with her big Dell PC about 10 years ago. We
didn't
get round to setting up the UPS for a couple of years. By the time we did
(and after the warranty had expired, inevitably) we found that it had
virtually no battery capacity: the battery monitoring software (monitored
by
USB connection) showed the battery accepting charge and gradually charging
up and eventually showing as fully charged, but as soon as the mains was
removed, the battery discharged within about 10 seconds with a nominal 40
W
lightbulb as the load. Utterly useless, and it wasn't even worth buying a
replacement battery for it because the fault may have been in the charging
circuit rather than the battery itself. APC didn't want to know when we
asked what a repair might cost, so it went in the skip - a waste of money
as
it was never even used.

Always test your emergency system. When I was in IBM, they tested the
emergency generators once a month. I have no idea why they had such
in the building I was in (just offices and a few labs at that time)
but they were there, so the were tested.

The office building where I worked had huge diesel-powered generator to cope
with power cuts. My office was near it, and I know it wasn't tested during
office hours for five years. One day there was a power cut that affected the
whole town, and the diesel engine fired up, amid a tremendous roar and lots
of filthy black smoke. Power returned for about a minute and then there was
a huge explosion and a jet of flames. Apparently the generator couldn't
handle the load, even with the engine working as hard as it could (a good
diesel grunt!) and something caught fire, igniting the diesel tank. Turned
out that it had been specced back in the days when there wasn't a PC on
every single person's desk, and it was woefully underpowered for the modern
demands that were placed on it.