On Tue, 14 Jan 2014 15:30:00 -0800, Jeff Liebermann
wrote:

On Tue, 14 Jan 2014 21:21:45 +0000, T i m wrote:

I have some block / logic diagrams but no schematic. ;-(

See if the fuser heater current goes through the thermostat. I
suspect that it does, which means the thermostat has to disconnect
under load. Nice way to create a small arc.

It does, both, they are in series with the heater / lamp.

* Heat Lamp : Kunckle Type

A what?

;-) Pass!

Thermostat
When a heat lamp is overheated, a Thermostat cuts off the main power
to prevent over-heating.

Main power as in the AC line power? I doubt that. Probably just the
fuser heater power.

Yup.

Adding a 2nd thermostat sounds like a retrofit to fix the problem.

Not the problem of going o/c I assume?

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.

The thermostat
would probably open a few times during such heavy duty printing. The
thermostats are not meant to survive too many such cycles. Rather
than welding the contacts shut, which would be a safety problem, like
a common household circuit breaker, they're made to open at ever
decreasing temperatures, eventually resulting in a permanent open
circuit. Note: this is a guess, this is only a guess.

Ok ...

Would the
fuser normally be running at full temperature when the (a) printer was
at idle?

No. Most laser printers have 3 or 4 levels of power savings. Then
printing, the fuser heater power is full blast. Between print jobs,
usually for about 10 minutes, the power is at about 30% of full blast.
If the printer goes into standby, the fuser power is at about 5-10%
which is just enough to get the first page printed reasonably fast and
avoid major inrush current. In shutdown, the fuser power is totally
off. I have no idea what Samsung does in this printer.

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).

What would you recommend then to cover a similar SOHO, networked
(wired) duplex mono role then Jeff?

I like the HP 2300DTN printer.

Googles It looks fairly 'chunky'?

http://h20566.www2.hp.com/portal/site/hpsc/public/psi/manualsResults/?cc=us&sp4ts.oid=238800
I own 3 of them, and have resold or arm twisted customers into buying
approximately 15 of them. The first page comes out in about 3
seconds. Duplex printing is handy to save paper, but is admittedly
slow. However, like all HP printers, these have a lifetime shortening
feature which I believe HP has ignored because it causes obscure late
term failures that sell many replacement printers.

Oh?

Here's the fix:
http://www.learnbydestroying.com/jeffl/hp2200/hp2200.html

Nice.

I've also found the same sticky solenoid problem in all HP printers of
the same vintage (2200, 2230, 4100, 4150, 4200, 4250, 4300, etc).
Also, you might have problems with magnetized solenoids:
http://www.learnbydestroying.com/jeffl/crud/hp2200-solenoid.wmv
You'll need an antique 1/4" magnetic tape bulk eraser to fix that.

Got one of those. ;-)

Otherwise, the 2300dtn have been a great printer.

I'm guessing that like many things (including cars) these days they
are designed to be disposable. ;-(

Todays design methodology is actually fairly simple and somewhat
economical. The manufacturer sets a target lifetime for the product.
He then cost reduces components and assembly techniques until
literally everything fails at the same time, somewhat after the target
lifetime. Anything that lasts longer than the target lifetime is
considered a waste of money and is further cost reduced. I can
critique HP's latest laser printer offerings on this basis, but I'm
late for a paying appointment.

Ok.

Luckily I have a mate with all the reflow gear. ;-)

I have a hot air SMT desoldering station. It doesn't work. The main
problem is that when the solder is hot enough to reflow, the blowing
air pushes the parts out of position. An IR reflow station is what
you want. However, I pizza oven or electric toaster oven is good
enough.
https://www.sparkfun.com/tutorials/60

Yeah, that's the sort of thing my mate has built / modded / bought
etc.

Oh, I contacted the supplier of the thermostat pair you kindly found
me and they have replied saying 5 off (minimum quantity) will cost me
80 USD delivered. Now, that's less than the cost of a new fuser but at
least with a new fuser I get a new fuser (as well). ;-)

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?

I have 2 x HPLJ 4's that I'm not sure what to do with.

eWaste.

Hmmm, shame.

p.s. I can't seem to get this Samsung to connect via WiFi. It 'sees'
al the local WiFi networks but doesn't want to connect to any (all
mine). The thing that worries me is that although I put the WPA
passphrase in in lower case it displays it in the status printout in
upper?

Temporarily clear the WPA encryption key from the wireless router and
see if it will connect with no pass phrase. If that works, try
entering a simple WPA2-AES pass phrase and see if that works. The
usual problem is that some devices enforce the 8 character minimum
pass phrase length, while others ignore it.

We have 8+ on all of them. I can do as you suggest but with a spare
router.

The other common problem
are Apple Airport base stations that need a firmware update in order
to coexist with other devices. Yet another are web forms that don't
like spaces in the pass phrase. The encryption key can have spaces
but the web form transfers the spaces as garbage. Isn't compatibility
great fun?

Isn't it just (not). ;-)

Gone...

looks around

Whoah, where did Jeff go ...?

Cheers, T i m