Turn off laser printer with power strip?

[Tony]

Gary what model?
I have several Minolta QMS service manuals and this company usually includes
circuit diagrams in their manuals. If I have the right manual I can provide you
with an absolute answer to your question.
For instance I quickly looked at the manual for the Magicolor 7300, and this
printer's power switch completely interrupts power to the printer immediately.
In this case you could pull the power cord from the wall and it would be no
different to operating the power switch, so a power strip would be perfectly OK.
If you would like me to do this please let me know the model number.
Tony

 

[Brendan R. Wehrung]

I'm not an engineer; I should have prefaced my post with "From what I
understand..." Nevertheless, here are some links that support my
understanding that it's unwise to use a surge protector with a laser
printer.

One of the two lasers I have on my computer (one old, one new, both
Samsung cheapies) draws enough current to cause my uninterruptible power
supply to cycle and drop power. So yes, it happens and is worth checking
with the manufactuerer for max power draw. Never happened with thenewer
printer.

Brendan

 

[John Smith]

w_tom:

You seem to like the phrase, "junk science reasoning without numbers."
Other than to use that phrase a few times to describe EMI/RFI filtering in
surge protectors, you offer nothing to back up your argument.

I'm looking at a new-in-the-box APC surge protector, Model SurgeArrest
Essential P6B. It took me about 5 seconds to find the following technical
specification numbers on the box:

20-55dB EMI/RFI Filtering

A quick check of APC's web site found the surge protector section. Partial
specs for one device
(http://www.apc.com/resource/include/techspec_index.cfm?base_sku=PF11VNT3)
include:

Surge energy rating: 2030 Joules
eP Joule Rating: 3400
EMI/RFI Noise rejection (100 kHz to 10 MHz): 70 dB

So your claim that EMI/RFI filtering is promoted "without numbers" is
groundless. In fact, in light of your claim that "n reality, a power
strip protector [sic] does nothing useful for a consumer," I realize you are
confusing the terms "power strip" and "surge protector." Though you may
have seen the insides of a common power strip, I suspect you have never seen
the insides of a surge protector. (Whatever you wish to call it, I also
dispute your claim that for a consumer the power strip / surge protector
device is useless.)

Meanwhile your logic is that if a fan in a printer or a car runs
after power off, then if fan does not run, damage will result.
Nonsense. Spin that only a politician could love. Does the laser
printer or car get hotter when powered off? Of course not. If a fan
does not spin, the laser printer and car still cool - just slower.

I did not say that damage will result after power off if a fan does not run.
I said that you may shorten the product's life by repeatedly letting it bake
in its own heat. If you had experience with leaky electrolytic capacitors
you would know that.

Your ad hominem attack is out of place in this technical debate.

Finally, I never said that the printer gets hotter when it's powered off.
(Although a car's engine block may get hotter immediately after the water
pump stops circulating cooling water, that's a discussion for another
forum.) I said exactly what you wrote: After being turned off, without
benefit of a fan the printer or car eventually gets cooler, but it takes
more time. Since heat can damage electronics by shortening its useful life,
it's advantageous to get rid of that heat whenever possible. That's why
most electronic equipment cases contain air vents. Thus, if an engineer has
designed a product so that its cooling fan continues running after the
product is turned off, turning off that cooling fan before it has finished
ridding the electronics of heat is counterproductive.

I mentioned overhead projectors earlier. After most models are turned off
with their switch, the fan continues to run for a few minutes to cool the
bulb. Unplugging the projector before the fan automatically turns off
defeats the cooling mechanism. The same principle applies to printers. See
http://www.modernsoundpictures.com/neumade-overhead-2002.html

This being a free country, you are of course free to cool or not cool your
own laser printer in any manner you so choose. Heck, if you don't think
they're important you can even disconnect the fans if you feel like it! But
I question the wisdom of second-guessing the engineering team that designed
the printer's fan cooling system in the first place: If they didn't think
it was necessary, they wouldn't have chosen a circuit that keeps the fan
running after power off.

 

[Arthur Entlich]

It depends. Some peripherals go into varying levels of sleep depending
upon how long they have been asleep for. Most are pretty conserving
these days.

If motors and heater are shut down, the other electronics, especially
when the lasers or scanning parts are not being used, use just a trickle
of power.

Art

 

[Arthur Entlich]

Most equipment today is well fused and not that easily damaged, even by
spikes. It's a good ad for their product and they probably rarely have
to pay out. It takes a fair spike to actually damage most modern
equipment (like a lightening strike).

Art

 

[Arthur Entlich]

Makes no difference whether power is removed by printer switch, power

strip, or wall switch.

I think your statement above is way too broad. Designs differ
considerably. Many off switches on printers actually do not shut down
the power fully, keeping trickle voltages to keep certain components
operational. Further, many do indeed have delays to allow certain
mechanical parts to be placed in the proper position for rest or
storage, and a power interruption can indeed leave these machines in a
vulnerable state.

Further still, heat build up can indeed still occur and warp or damage
parts if cooling fans are cut off too soon. Fans can be used to
maintain a specific temperature range that can be overshot by a heated
part without air circulation, even if the part is no longer being
supplied with addition energy to maintain its heat.

Art

 

[Davy]

Not ALL surge potectors provide EMI/RF shielding as I think someon
stated, many type are the plain ol' MOV (Metal Oxide Varistor), it'
a resistor that lowers it's value with sudden increase in voltages
don't confuse this with a thermistor which changes its resistanc
with temperature

For EMI/RF sheilding you'll need RF chokes and capacitors or ferrit
rings and clamps

Dav

 

[w_tom]

Your speculating - then trying to justify that speculation as fact.
If residual heat caused other damage, then the manufacture would state
that is a problem. Where is that 'speculated problem' stated in the
manuals? Yes, it may be possible for heat to harm some other
component. Fine. Which compnents? Possible heat damage which is why
the manufacturer warns us not to remove power. Ahh... where is that
warning? A damning missing detail.

I have worked on laser printers. Fixing them to better understand
them. I don't see this susceptible component? I don't see these
warnings about not removing power. Where does this fear come from?
Speculation.

 

[w_tom]

The other post did not provide numbers. So now you have provided
numbers. Good. 20-55dB of filtering. At what frequencies? IOW an
incomplete number that should be obvious if you had technical
knowledge. Furthermore, what filtered noise frequencies cause damage
to a laser printer? Now that you have provided numbers, you are being
challenged to prove your claim with those numbers. Numbers do not
support your claim that:

It's generally not a good idea to power laser printers (or any other
devices that draw large amounts of current, ...) through a surge
protector because they interfere with the surge protection capability.

Am I to assume that 20-55 dB filter is damaged by high current
devices? Am I to assume that 20-55 dB filter no longer filters if high
current devices are used? Clearly you don't make the point. You don't
even provide a technical explanation of "interfere". You only post
numbers that apparently you don't understand and that are not relevant
to your claims. This is about your integrity which the numbers should
cause all to suspect.

Provided was the joules number: 2030. OK. What was the let-through
voltage for those 2030 joules? Another number not provided. So I will
guess. 330 volts. IOW those 2030 joules are electrically non-existent
(open circuited, disconnected, not shunting) when AC voltage remains at
a normal 120 volts. So again, how do those 'disconnected' parts prove
a power strip protector harms a laser printer? Once we include the
number you did not provide - 330 volts - then the laser printer
connects direct to AC mains.

EMI/RFI filtering for 100,000 to 10,000,000 Hz. Why provide that
number? They are limits defined by FCC so that appliances don't radiate
noise. Where does that number have any affect on 60 Hz electricity or
on how the laser printer works? What does the laser printer already
have? Filters for those same frequencies. So that filter inside the
laser printer harms or "interferes" with the laser printer? Why do you
provide numbers that prove nothing?

Same applies to claims about heat doing damage. Total speculation.
Where are the numbers from that manufacturer warning about not removing
power? Yes, you provide numbers this time ... that are totally
irrelevant ... which makes me wonder how many more technical claims are
made without first learning.

Why do we demand numbers? So that a poster demonstrates a grasp of
the technology. Junk scientists don't provide numbers because they
will be exposed as liars. In this case, I still see no numbers that
demonstrate how high current devices "interfere" with surge protector
abilities. I don't see any numbers that even claim those surge
protectors' abilities. And I don't see any technical facts that
suggest removing power from a power strip or wall switch is
destructive. I see lots of speculation that is not justified by the
numbers provided.

You do have the right to lie to others. And others have the right to
challenge you to provide the numbers. You still have not provided any
numbers to justify your claims that high current devices "interfere"
with surge protector abilities. These claims are too common among
those who never first learn the technology. I hope these bruises will
reming you to first learn science before speculating.

Brutal response? Yes. I did not spend decades learning this stuff
only to have a wild speculator claim to be just as knowledgeable. Junk
science reasoning is too common among mankind. Too many English majors
are now technical experts. If you post wild speculation - if you post
to intentionally deceive others - then expect to be challenged this
vigorously.

Meanwhile, you don't have numbers that show this protector
"interference" AND you are only speculating about heat damage.
Your reasoning: a fan spins - therefore damage will obviously result
if the fan does not spin. Wild speculation, no numbers, and not even a
manufacturer citation.

w_tom:

You seem to like the phrase, "junk science reasoning without numbers."
Other than to use that phrase a few times to describe EMI/RFI filtering in
surge protectors, you offer nothing to back up your argument.

I'm looking at a new-in-the-box APC surge protector, Model SurgeArrest
Essential P6B. It took me about 5 seconds to find the following technical
specification numbers on the box:

20-55dB EMI/RFI Filtering

A quick check of APC's web site found the surge protector section. Partial
specs for one device
(http://www.apc.com/resource/include/techspec_index.cfm?base_sku=PF11VNT3)
include:

Surge energy rating: 2030 Joules
eP Joule Rating: 3400
EMI/RFI Noise rejection (100 kHz to 10 MHz): 70 dB

So your claim that EMI/RFI filtering is promoted "without numbers" is
groundless. In fact, in light of your claim that "n reality, a power
strip protector [sic] does nothing useful for a consumer," I realize you are
confusing the terms "power strip" and "surge protector." Though you may
have seen the insides of a common power strip, I suspect you have never seen
the insides of a surge protector. (Whatever you wish to call it, I also
dispute your claim that for a consumer the power strip / surge protector
device is useless.)

Meanwhile your logic is that if a fan in a printer or a car runs
after power off, then if fan does not run, damage will result.
Nonsense. Spin that only a politician could love. Does the laser
printer or car get hotter when powered off? Of course not. If a fan
does not spin, the laser printer and car still cool - just slower.

I did not say that damage will result after power off if a fan does not run.
I said that you may shorten the product's life by repeatedly letting it bake
in its own heat. If you had experience with leaky electrolytic capacitors
you would know that.

Your ad hominem attack is out of place in this technical debate.

Finally, I never said that the printer gets hotter when it's powered off.
(Although a car's engine block may get hotter immediately after the water
pump stops circulating cooling water, that's a discussion for another
forum.) I said exactly what you wrote: After being turned off, without
benefit of a fan the printer or car eventually gets cooler, but it takes
more time. Since heat can damage electronics by shortening its useful life,
it's advantageous to get rid of that heat whenever possible. That's why
most electronic equipment cases contain air vents. Thus, if an engineer has
designed a product so that its cooling fan continues running after the
product is turned off, turning off that cooling fan before it has finished
ridding the electronics of heat is counterproductive.

I mentioned overhead projectors earlier. After most models are turned off
with their switch, the fan continues to run for a few minutes to cool the
bulb. Unplugging the projector before the fan automatically turns off
defeats the cooling mechanism. The same principle applies to printers. See
http://www.modernsoundpictures.com/neumade-overhead-2002.html

This being a free country, you are of course free to cool or not cool your
own laser printer in any manner you so choose. Heck, if you don't think
they're important you can even disconnect the fans if you feel like it! But
I question the wisdom of second-guessing the engineering team that designed
the printer's fan cooling system in the first place: If they didn't think
it was necessary, they wouldn't have chosen a circuit that keeps the fan
running after power off.

 

[Fred McKenzie]

It's my understanding that even in "sleep" or "standby" mode most electrical
devices still consume a significant amount of power. Please feel free to
correct me on this if I'm wrong.

Gary-

"Significant amount of power" is relative. Compared to full-up power
consumption, it is very small.

If you were to use the printer frequently, say five or six times a day,
then the standby power might be five or ten percent of total power
consumption.

If you only print once a week, there is no excuse for leaving the printer
on in standby. Even if leaving it on keeps its innards dry and ready for
immediate printing, it would be wasteful. Each Watt of standby power
burns 8.76 KiloWatt Hours a year.

Fred

 

[Bob]

However, why then do the surge protectors sold in the UK (where I am)
often come with £10,000 or whatever protected equipment cover - "if
you get a spike and your equipment behind this surge protector is
damaged we'll buy you a new one". Are the manufacturers banking on
no-one taking them up on it?

Exactly. Who has that paperwork around when it's time to make a claim?
Even with it, you have to meet all the qualifications of the fine
print . Lastly, very, very few devices can be proven to have been
damaged by a surge, so very few claims are made.

As to the ability to protect... the surge protector just diverts the
surge (if it is big enough to even light it up) down the ground wire.
The premises ground wire it to small a gauge to handle really large
surges but it does accommodate the smaller ones. The surge does not
actually go to ground though, because that's a long way away down
another wire that is too small (who's purpose is to ground the
electrical system, not perform things like lightening protection).
Instead, it looks for the path of least resistance. Typically it will
find it along the way and fry something else, or it will find it when
it gets to the power panel where (in the USA) the neutral is tied to
the ground circuit. A surge protector on one device can protect it -
and ensure you fry something else. Probably not what you expected when
you bought one.

I seem to recall something about the UK wiring code typically have a
round robin sort of arrangement within a room that sounded more open
to this problem when I read it, but it't been a long time since I did.

The bottom line though is that very few devices are likely to ever be
damaged by a surge short of a nearby lightning strike. Power lines and
levels are not that unstable for most of us. If they are, you need a
UPS anyway (where the device runs off a charged battery, not line
voltage). The levels that the surge protector has to hit to kick in
are high, higher than any normal line surge. And, if you get hit by
lightning, no device based surge protector will ever, ever, protect
you. That would require premises protection with a serious ground
plate (lot of rods, or copper strips buried, using a very short, very
large gauge wire to connect from the protection device to the true
ground. FYI - those devices are actually only about $50 but might cost
a tab more to install as they have to go at the service entrance and
you need a licensed electrician to do it.

Bob

That took too long to write, I'm outta here!

 

[Arthur Entlich]

I am not speculating. I have repaired laser printers, and indeed, even
with "designed" heat removal via fans and heatsinks, parts do overheat
and permanently warp. There was one HP early color printer that had a
continual problem with this, causing parts of the case to warp and
eventually leading to an open door error developing because the case
form changed. Several other brands have had similar problems. I do not
know of any laser printer manufacturer that suggests regularly turning
off the printer after an activity before the unit's cooling fans go off.
Power bar switches are 3rd party products and switching a peripheral
off in that manner is equivalent to yanking the plug on it,

I have a better question... why do the engineers design there to be
cooling fans running on these devices if they want you to turn them off
at will?

Inkjet printer companies don't warn you that the printer may suddenly
stop working right in the middle of a project and have to be brought in
for a EPROM reset and change of the waste ink pads either, you just find
out when it happens. Nor do they warn that a clogged head on an inkjet
printer that uses a microchipped cartridge may falsely lower the ink
level it monitors even though the ink may not be leaving the cartridge
at all.

There are millions of things which appliance companies do not "warn" the
end user about, because they either don't wish them to know, or they
consider the action obtuse or not logical to engage in. Many designs
today especially use materials and systems that are designed just within
the known tolerances they can work at, and repeatedly pushing beyond
that will shorten their lives

Art.

 

[Bob]

There are millions of things which appliance companies do not "warn" the
end user about, because they either don't wish them to know, or they
consider the action obtuse or not logical to engage in. Many designs
today especially use materials and systems that are designed just within
the known tolerances they can work at, and repeatedly pushing beyond
that will shorten their lives

Kind of like LCD projectors... they tell you not to shut them off
without going throught the cool down - but only the guy who has to
shell out $500 for a new bulb that is only good for 1000 hours at best
*with* proper care really takes it to heart.

Of course, until you call up and find out the bulb is $500 the first
time, you may not pay heed to the warning.

 

[w_tom]

Ink jet printer manual warns a user to not switch off power.
Projector manufacturers with bulbs that require power down cooling also
provide the appropriate warning. No such warning is found with laser
printers.

Why would that extra seconds of cooling be installed in a laser
printer? So that bulb does not remain excessively hot when human hands
enter the machine.

However Arthur Entlich provides a first good reason for leaving a
printer powered until fan turns off. He notes damage that he
attributes to heat damage. A good reason for letting the cooling fan
first turn off before removing power. Once that fan turns off, then
still, laser printer can then be powered down by a switch.

EPROMs are not ever reset. EPROMs are read only devices - nothing to
reset. Furthermore, if a printer does not automatically reset itself

 

[Tony]

Many (most, in my experience) laser printers are isolated completely by the
power switch, but some are not. If they are not then it is for a reason. I have
no doubt at all that it is to dissipate heat from within the cabinet. The fuser
may well be at 200 degrees Celsius and that heat has to go somewhere, I am sure
that the the fans keep running to ensure that some of that heat is not applied
to components that are not designed to withstand those temperatures without
cooling.
There is no way that a fuser will cool down so it is safe to touch in only a
minute or two, most manufacturers recommend that a cool down period of at least
20 minutes be applied before fuser removal; fusers have a high degree of
thermal retention, they are designed that way. I do not believe that the short
period of fan operation after power down is to make the printer safe for people
to open since they can open it with power on in nearly all cases, and with many
printers can get a slight burn (however there is always a degree of physical
protection designed into the printer).
I am sure that Arthur meant to type EEPROM (similar to NVRAM), we all make
typos don't we?
Tony

 

[Arthur Entlich]

EPROMs are not ever reset. EPROMs are read only devices - nothing to

reset. Furthermore, if a printer does not automatically reset itself
on power up, then we all want to know what printer to avoid as
defective by design.

Sorry, it was a typo, I meant an EEPROM.

Most inkjet printers maintain timing between cleanings, ink use
counters, and amount of ink stored in the waste ink pads (protection
numbers). These can get scrambled or misread if the printer is turned
off from a power bar rather than the I/O switch. Also, if the printer
has not properly capped the heads beforehand, they can be left uncapped
or partially capped if shut down via a power bar switch rather than the
i/o switch. But some of this is discussed in the manual.

However, inkjet printer companies don't warn you that the printer may
suddenly stop working right in the middle of a project and have to be
brought in for a EEPROM (is that better?) reset and change of the waste
ink pads either, you just find out when it happens. Nor do they warn
that a clogged head on an inkjet printer that uses a microchipped
cartridge may falsely lower the ink level it monitors even though the
ink may not be leaving the cartridge at all.

My point is that not everything you should know to operate the printer
is necessarily in the manual.

Art

 

[Arthur Entlich]

Thanks Tony,

It was a typo, and yes, it was supposed to read EEPROM.

Art

 

[w_tom]

We don't reset EPROMs and we don't reset EEPROMs. Look inside a
computer. If configuation data is routinelymodified in EEPROM, then a
computer would not need that battery for CMOS battery backup. Why does
the motherboard - using EPROM or EEPROM - still store parameters like
disk drive settings in battery backup RAM? Because EEPROMs have
limited life expectancy when written to. EEPROMs are rarely (ie during
a BIOS upgrade) written to, and are read often.

Printer would not repeatedly update configuration data in an EEPROM
for same limited write-only reasons and for a few other reasons. Any
data reset would be in a battery backup memory (or use some other
electrical backup equivalent to battery).

It was a minor point. But it says much about how rumors are created.
There is no EEPROM to reset. And as I said before, any printer whose
EEPROM must be reset by a tech - we want to know that printer brand
name so we never buy from that manufacturer again.

EPROMs are read only devices. EEPROMs are 'read many, write few'
type devices. If an EEPROM was constantly written to by a printer's
computer, then the EEPROM would fail prematurely. No EEPROM
'configuration writes' exist on any reliable printer - for same
technical reasons why a computer's CMOS data is also not stored in
EEPROM.

 

[Tony]

The following are demonstrable facts.
HP use EEPROMS in many of their laser and inkjet printers
Canon use EEPROMS in many of their inkjet printers
Brother use EEPROMS in many of their inkjet printers
OKI use EEPROMS in many of their LED printers
Epson Use EEPROMS in many of their laser and inkjet printers
Lexmark use EEPROMS in many of their laser printers
If you want model numbers I can provide them. I bet the above list is
incomplete.
This is personal knowledge without doing any research, I suspect that the use
of EEPROMS is almost universal with printer manufacturers although some use
NVRAM in some models and EEPROMS in other models.
They are mostly capable of being reset by the user or a technician but more
importantly are in most cases updated at least every page.
I have fixed thousands of printers and have never seen an EEPROM failure,
although there may have been a small number of main board failures that were
actually EEPROM failures but were not diagnosed to that level. I cannot accept
that they will fail prematurely.
Tony

 

[Arthur Entlich]

OK, smarty with your royal "we", since you won't let this ride...

I own nearly every Epson inkjet printer service manual. I refer to them
almost daily in some form or another. They not only have words and
pretty drawings and photos in them, but circuit diagrams, and even
charts showing the EEPROM data structure. They use the term EEPROM in
every manual and they specifically discuss when and why and how the
EEPROMS are reset and rewritten to. Go check them out and argue with
Epson if you don't like their terminology. Some data is stored in
battery backed up storage devices, some is stored via "EEPROMs". The
"EEPROMS" require resetting when the waste ink pad protection numbers
are exceeded, as I stated. Although I would think that Epson and their
translators would know what an EEPROM is, maybe the term is inaccurate.

Honestly, I couldn't care less. If you do, why not research it and
write Epson if the usage is incorrect. Personally, I tend to believe
Epson has used the term correctly, but I am not as anal retentive as you
apparently are. The original point revolved around what might happen if
certain printers are turned off at the plug rather than at the switch,
and this issue of EEPROMS was quite secondary to that.

Further, if you are that interested, Epson uses some type of memory
device on their cartridges, which monitors ink usage. They are written
to each time the printer is turned off and they can be reset and reused
for what appears to be indefinitely. They have no energy source. Maybe
its a couple bites worth of flash memory.

Art