I've got a laserjet 4M and there has always been a slight delay between
switching it on and it powering up. Now the delay can be a couple of
minutes if it's not been switched on for a couple of weeks.

I haven't pulled it apart yet but I was wondering if it's a known
common problem. It's not worth me getting a new power supply with
injets being so cheap these days.

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail ngpsm4 (at) infohitsystems (dot) ltd (dot) uk

Probably dried out electrolytic caps. You should measure their ESRs to
know which ones need to be changed. If there is not very lot of caps,
you can also try to change them all, except the one(s) as main filter
right after mains rectification.

--
Top-posting not suppoorted.

You'd replace a HP laserjet with a crappy inkjet?! Wow..


It's not worth me getting a new power supply with
injets being so cheap these days.

"Rodney Pont" ) writes:
I've got a laserjet 4M and there has always been a slight delay between
switching it on and it powering up. Now the delay can be a couple of
minutes if it's not been switched on for a couple of weeks.

I haven't pulled it apart yet but I was wondering if it's a known
common problem. It's not worth me getting a new power supply with
injets being so cheap these days.

I believe the proper last sentence is "It's not worth me getting a new
power supply with laser printers being so cheap these days".

I had an inkjet, an Apple Stylewriter bought used for twenty dollars
in 2001. When I filled up the ink cartridge, I was really disappointed
by how little I could print before I had to refill. And I realized
early on that the ink so easily smears when it gets wet.

A few months later, I got an old TI laser printer for $25 at a school
rummage. That lasted a while, but when it ran out of ink, I was
uncertain about it's state so I simply replaced it with another used
laser printer. The second one cost me only $15, but it was an HP Laserjet
4P. It had fewer pages on it than the TI, and had no problem from the start
(unlike the TI that had some slight printing problem that might have simply
been the lack of toner). It's lasted longer than the TI in my hands,
and I don't foresee it going bad.

But if it does, I'll simply buy another used laser printer for about
the same amount. And if those run out, I can buy a laser printer new
for under a hundred dollars, which is far less than I paid for my first
dot matrix printer in 1982, or my first daisywheel printer in 1984.

Michael

"Michael Black" wrote in message
...

But if it does, I'll simply buy another used laser printer for about
the same amount. And if those run out, I can buy a laser printer new
for under a hundred dollars, which is far less than I paid for my first
dot matrix printer in 1982, or my first daisywheel printer in 1984.

I just bought a Brother all in one laser for about $110 after rebates.
Cheaper than the replacement drum unit!

Michael Black wrote:

"Rodney Pont" ) writes:
I've got a laserjet 4M and there has always been a slight delay between
switching it on and it powering up. Now the delay can be a couple of
minutes if it's not been switched on for a couple of weeks.

I haven't pulled it apart yet but I was wondering if it's a known
common problem. It's not worth me getting a new power supply with
injets being so cheap these days.

I believe the proper last sentence is "It's not worth me getting a new
power supply with laser printers being so cheap these days".

I had an inkjet, an Apple Stylewriter bought used for twenty dollars
in 2001. When I filled up the ink cartridge, I was really disappointed
by how little I could print before I had to refill. And I realized
early on that the ink so easily smears when it gets wet.

A few months later, I got an old TI laser printer for $25 at a school
rummage. That lasted a while, but when it ran out of ink, I was
uncertain about it's state so I simply replaced it with another used
laser printer. The second one cost me only $15, but it was an HP Laserjet
4P. It had fewer pages on it than the TI, and had no problem from the start
(unlike the TI that had some slight printing problem that might have simply
been the lack of toner). It's lasted longer than the TI in my hands,
and I don't foresee it going bad.

But if it does, I'll simply buy another used laser printer for about
the same amount. And if those run out, I can buy a laser printer new
for under a hundred dollars, which is far less than I paid for my first
dot matrix printer in 1982, or my first daisywheel printer in 1984.

Michael


My first "Printer" was a pair of heathkit H-14 printers, in pieces in
a box for $20 at the Cincinnati hamfest in 1983. Both were missing the
masked ROM CPU, which set me back another $30. It was RS-232 with
square print wires, but it did a nice job. I found out later that it was
the same printhead and drive motors used in Diebold ATMs, and dug about
20 defective ATM printers out of their dumpster when I worked next door
to their service center in Orlando. I still have a few good, spare
print heads, somewhere. ;-)

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Rodney Pont wrote in message:
atcfzvasbuvgflfgrzfygqhx.j8s7hz1.pminews@ouse,

I've got a laserjet 4M and there has always been a slight delay
between switching it on and it powering up. Now the delay can be a
couple of minutes if it's not been switched on for a couple of weeks.

I haven't pulled it apart yet but I was wondering if it's a known
common problem. It's not worth me getting a new power supply with
injets being so cheap these days.

Lasers are plenty cheap these days as well. The HP Laserjet 1020 is very
inexpensive if you do a little shopping around.

--
DVDs for sale:
Banned Cartoons Collection, http://banned-cartoons.com
The Unknown War documentary series, http://unknown-war.com
The Centennial miniseries, http://centennial-dvd.com

On 15 Nov 2006 04:59:57 -0800, Simoc wrote:

Probably dried out electrolytic caps. You should measure their ESRs to
know which ones need to be changed. If there is not very lot of caps,
you can also try to change them all, except the one(s) as main filter
right after mains rectification.

Thanks for the suggestion Simoc.

I had thought of caps but if it's been on 24 hours previously it only
takes 2 seconds before powering up yet if it's been a week it takes 2
minutes. Can you see a cap in the power supply not fully discharging in
24 hours? Then there is the ten years I've had the printer and it's
occasionally gone a couple of weeks between being used, surely the caps
would have discharged in that time and I would have seen the same
problem.

I was thinking more along the lines of a battery to be honest, maybe on
the processor board. There isn't any obvious damage to the psu and no
caps are leaking or bulging.

Thanks also to all who suggest I stay with laser printing :-)

This one has done sterling work and was a real second hand bargain when
I got it. Times change though and I'm now effectively a home user who
may want to print the occasional web page or letter and possible
photographs in the future. Even a modern cheap laser will do something
like 2000 sheets from a toner cartridge and I just can't see me
printing that much in the next 10 years.

I'm not dumping this printer while it still works though and I can't
see me buying an inkjet while this does still work. Lasers are real
value for money printers providing you use them but the consumables do
so many sheets that I'm never going to use them up. The previous toner
cartridge didn't run out of toner, the transfer roller aged first and I
was using it a lot more than I do now.

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail ngpsm4 (at) infohitsystems (dot) ltd (dot) uk

Rodney Pont wrote:
Thanks for the suggestion Simoc.

You're welcome.

I had thought of caps but if it's been on 24 hours previously it only
takes 2 seconds before powering up yet if it's been a week it takes 2
minutes. Can you see a cap in the power supply not fully discharging in
24 hours? Then there is the ten years I've had the printer and it's
occasionally gone a couple of weeks between being used, surely the caps
would have discharged in that time and I would have seen the same
problem.

Bad caps cause exactly that kind of behavior. You just have missed some
of the theory, I explain:

You are probably thinking, that the 2 mins would be normal when they're
discharged. But not, that's not the point. If the caps were good, they
would charge virtually immediately when powered, even if they're fully
discharged. That explained your last sentence (as then the caps weren't
dried out yet).

But as they are now dried out due to aging, their ESRs have increased
and that reduces both the charge and discharge current, causing too
much ripple voltage (and thus preventing the device from working). They
probably get discharged within 24h, but the point is there, that those
caps get _temporarily_ "rejuvenated" (ESRs decrease) when power is
applied for long enough time (the 2 min), by causing them to heat up.
But once the device is turned off, the caps cool down and then the
"rejuvenation" begins to lose its effect (ESRs begin to increase again)
_slowly_ (not immediately when cooled down and discharged, but within a
few days).

So the dried out caps should be replaced with new ones. Easy repair :-)

I was thinking more along the lines of a battery to be honest, maybe on
the processor board.

What battery? If there is one (I'm doubting), it's for memory back-up
and if bad, it would cause the device not to remember settings when
disconnected, but it doesn't cause the delayed start-up.

There isn't any obvious damage to the psu and no
caps are leaking or bulging.

Bad caps don't bulge nor leak in most cases (although sometimes do).

--
Top-posting not supported.

On 19 Nov 2006 09:20:36 -0800, Simoc wrote:

You are probably thinking, that the 2 mins would be normal when they're
discharged. But not, that's not the point. If the caps were good, they
would charge virtually immediately when powered, even if they're fully
discharged. That explained your last sentence (as then the caps weren't
dried out yet).

But as they are now dried out due to aging, their ESRs have increased
and that reduces both the charge and discharge current, causing too
much ripple voltage (and thus preventing the device from working). They
probably get discharged within 24h, but the point is there, that those
caps get _temporarily_ "rejuvenated" (ESRs decrease) when power is
applied for long enough time (the 2 min), by causing them to heat up.
But once the device is turned off, the caps cool down and then the
"rejuvenation" begins to lose its effect (ESRs begin to increase again)
_slowly_ (not immediately when cooled down and discharged, but within a
few days).

So the dried out caps should be replaced with new ones. Easy repair :-)

I understand that now, just like a car battery that's duff could have
virtually no charge when cold but when warmed up works. I wasn't
looking at it from that point of view, I was just thinking how could a
change of capacitance affect performance depending on how long it had
been off, as you guessed :-)

There is only about half a dozen electrolytic caps and it's only a
single sided board so I'll take them out and test them. You said not
the mains filter cap(??), there is a 400V 1000uF (or 100uF can't
remember which) in there and I assume that's the mains one and it may
have a slight bulge on the top. Any particular reason not to go near
that one?

Thanks again, I'll go inside it again sometime, hopefully before I need
to print something.

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail ngpsm4 (at) infohitsystems (dot) ltd (dot) uk

Rodney Pont wrote:
There is only about half a dozen electrolytic caps and it's only a
single sided board so I'll take them out and test them.

Ok, do you have an ESR-meter? I want to highlight, that the capacitance
measurement doesn't tell reasonably the condition of the cap, as the
capacitance very rarely goes out of tolerance when the cap goes bad.
It's the ESR (equivalent series resistance) instead, like I've already
mentioned. It increases due to aging.

If you have an ESR meter accessible, good. But if not, your chances to
deal with this case a
-to buy one
-to build one: http://ludens.cl/Electron/esr/esr.html
-to just replace all the caps with new ones
-to test the caps by using a function generator and an oscilloscope
instead

The latter method is done by tuning the gen to a high freq, something
around 50kHz, with 100-200mV amplitude, connecting the cap in series
with the gen output and scope input, and scoping if the cap causes
significant attenuation by comparing the amplitude with and without the
cap in series.

You said not
the mains filter cap(??), there is a 400V 1000uF (or 100uF can't
remember which) in there and I assume that's the mains one

Yes.

and it may
have a slight bulge on the top. Any particular reason not to go near that one?

Not for not going near it. I just meant that if you decide to do the
method of replacing all the caps (if you haven't equipment for testing
them), then I would leave the mains one alone, as they fail very
rarely, and are also the least critical. So the small ones in chopper
circuits are both far faster to decay with age, and also much more
critical, and a small ESR on those can cause an appliance to completely
cease working, while the mains one in many cases outlast the device in
good condition, and might work well even with slightly increased ESR.

I've never experienced a mains cap having to be replaced except in over
30 years old antique equipment.

But however, I'm still not claiming that it couldn't fail, and if you
are suspecting it, replace it too if you're still gonna do the
replace-them-all-method. But if you are gonna make ESR measurements, of
course, the mains one should be measured as well, and treated according
to it. But some caps (especially those bigger ones) look like "little
bulged" just normally.

--
Top-posting not supported.

On 20 Nov 2006 06:25:25 -0800, Simoc wrote:

Ok, do you have an ESR-meter? I want to highlight, that the capacitance
measurement doesn't tell reasonably the condition of the cap, as the
capacitance very rarely goes out of tolerance when the cap goes bad.
It's the ESR (equivalent series resistance) instead, like I've already
mentioned. It increases due to aging.

If you have an ESR meter accessible, good. But if not, your chances to
deal with this case a
-to buy one
-to build one: http://ludens.cl/Electron/esr/esr.html
-to just replace all the caps with new ones
-to test the caps by using a function generator and an oscilloscope
instead

I knew absolutely nothing about ESR. I'd seen it mentioned here but
never thought to look into it. I suppose as a field tech I wasn't
expected to diagnose to that level but even when I sent things to the
workshop the only feedback I used to get was 'we replaced them until it
worked'. I don't think I ever managed to fix a switched mode PSU and
even on days I spent in the workshop I avoided them. My problem was all
the components seemed to test ok and I bet it was ESR... I can't say
how grateful I am for the lesson and I think I've just got to build a
meter :-)

A couple of years ago I was given a Sony 25inch TV with the picture
folding over but even knowing it's bound to be a capacitor I've put off
looking at it...

Thanks again.

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail ngpsm4 (at) infohitsystems (dot) ltd (dot) uk

Rodney Pont wrote:
I can't say
how grateful I am for the lesson and I think I've just got to build a
meter :-)

You're welcome. Btw, I really recommend building the meter on the Homo
Ludens site, I've built that, it works very well and is very useful.

Good luck :-)

--
Top-posting not supported.

Simoc wrote:
You're welcome. Btw, I really recommend building the meter on the Homo
Ludens site, I've built that, it works very well and is very useful.

Forgot to say, that you can see approx. highest acceptable ESRs of new
caps he

http://members.ozemail.com.au/~bobpar/2003esrchart.txt

It's acceptable that they rise a little, from those values but how
much, depends of the purpose...
--
Top-posting not supported.

Simoc wrote:

Rodney Pont wrote:
I can't say
how grateful I am for the lesson and I think I've just got to build a
meter :-)

You're welcome. Btw, I really recommend building the meter on the Homo
Ludens site, I've built that, it works very well and is very useful.

Good luck :-)

--
Top-posting not supported.

I recommend this ESR meter:
http://members.ozemail.com.au/~bobpar/esrmeter.htm

I have not tried the Ludens one.

Chris