On Wed, 15 Jan 2014 09:08:51 -0800, Jeff Liebermann
wrote:

On Wed, 15 Jan 2014 01:41:27 +0000, T i m wrote:

My wild guess(tm) is that the 170C was too low in temperature to stay
closed while the printer was being used as a printing press. The
manufacturer usually recommends a duty cycle, such as 20 mins print,
10 minutes rest, etc which of course, nobody follows.

Hehe.

Before electronic filing, my tax preparer customers would run their
laser printers almost full time during late tax season. Five inch
thick returns were common.

Wow.

A floor fan blowing on the printer was
also common. All of them went through the same exercise. They would
buy a cheap laser printer, run it like a printing press, destroy it,
and then buy something more suitable.

The guy opposite has done similar with a few small Brother and Samsung
mono lasers. I think he has since been given something bigger. ;-)

HP is unique in that it has a built in safety feature to prevent
overheating and over use. It's the sticky solenoid and foam rubber
pad I mentioned in a previous rant. When the machine is cold, the
solenoids work normally. However, as the solenoid becomes hot from
use, the glue and foam rubber pad melts, causing the solenoid armature
to stick to the frame. The timing error usually produces a paper jam
which offers the user a chance to slow down while practicing
profanity.

Hehe.

There has been some suggestion the sticky foam safety feature is not
intentional, but I suspect otherwise.

weg

HP has used exactly the same
design for their sticky solenoid safety feature since the HP LJII
which suggests that it's a successful method of controlling the
printing duty cycle.

;-)

Well, I've set it to 'sleep' after 5 mins and after 30 mins you can
still feel warmth coming out of the paper exit port (I assume that to
also be a thermal vent for the fuser).

I use a Kill-a-watt AC power meter to measure power consumption in
various states. Occasionally, my measurements agree with the data
sheet. You might want to measure the standby and power save power
consumption, which offer clues as to the fuser power consumption.

Approximate values.
Warm-up power mostly 900W for about 30 seconds.
12 or 900W on a 7:1 duty cycle after that.
After 5 mins it sleeps to a constant 10W.

Printing 3 colour pages from standby:
Going from 45 (motor running) to 900+W (fuser on + motor running +
paper handling) for the duration of the print process then back to 12
- 900 (7:1 duty cycle) till standby.


I like the HP 2300DTN printer.

Googles It looks fairly 'chunky'?

It's bigger than your P2025 but not as big as a production printer
such as a 4150, 4250, or 4300. Certainly smaller than an 8000 series
printer. Two of mine show about 80,000 pages.

!

My (new to me) Samsung:
Total Page Count : 3260 / 1976 Page(s) (Color/Mono)
Toner Page Count :
( Yellow / Magenta / Cyan / Black ) ( 998 / 995 / 994 /
731 ) Page(s)
Fuser Life : 14995 Page(s)
Transfer Roller Life : 5223 Page(s)
Tray Roller Life : 5236 Page(s)
Total Image Count : 15040 Image(s)
Imaging Unit Life : 15040 Image(s)
Transfer Belt Life : 15040 Image(s)
ADF Scan Page Count : 176 Page(s)
Platen Scan Page Count : 187 Page(s)

.... an I think it's done that over a few years.


The other is at about
10,000 because I replaced the formatter board. I replace most of the
rubber parts when I rebuild a printer. I get about 5000 pages per
toner cart. If you want better, you'll have to live with bigger.

Quite.

I think I can find a replacement single thermostat in the US for much
less. Later tonite...

Oh, cool, thanks (but aren't we still unsure what role both devices
covered? Stat+backup stat. Stat+Overtemp Stat? Stat+Thermal fuse?

Yep. If my guess is correct about thermostat cycling due to excessive
use, putting in the wrong thermostat will make it worse if set to a
lower temperature, or melt the fuser if set to a higher temperature.
At this point, I would so some measuring with an IR thermometer or
thermocouple. My guess(tm) is that the operating temperature is too
close to the thermostat temperature.

So, you feel the temperature is being controlled via the thermistor
controller PSU rather than the stats? That they are just there for
over temp?

I guess if I pop the side off (now I know how) I can (carefully, 240V)
monitor the feed to the fuser heater and see if it's 'switched' at
that point. If it isn't yet the machine current is still fluctuating
then it must be the stat that is managing the temperature (rightly or
wrongly etc)?

Cheers, T i m

p.s. The guy who can supply the stats can also supply the complete new
fuser and I'm currently awaiting his reply on that.