On Tue, 14 Jan 2014 08:44:28 +0000, T i m wrote:
Duz this sound familiar?
http://www.fixyourownprinter.com/forums/printer/72871
I'll try the 'impact reset' test and the good thing is you can
check the result there and then (with yer DMM).
I rarely see broken mechanical thermostats. More commonly, on HP
printers, I see accumulated toner residue piled up between the fuser
roller and the thermostat. Usually, there's some type of film between
the two, which prevents scratching the drum. I don't think I've ever
seen a blown thermostat on an HP which makes me wonder if replacing
the 170C thermostat with an identical Samsung part is a good idea.
Yes, I've since spotted that. The problem is though, if they are both
thermal switches and of different temperatures (the second / higher to
be used more as a failsafe in case the first / normal switch sailed
unsafe) then we don't know which one on mine is still functional?
I don't have a schematic, but I'll guess(tm) that they are running
some serious heater current through the thermostat, causing the
contact to possibly arc. A few protective arcs under load, and the
contacts will build up a layer of oxidized copper which makes a fair
insulator. This is the power supply relay contacts of an HP LJII with
a similar problem:
http://www.learnbydestroying.com/jeffl/pics/drivel/slides/hp-relay.html
The little back dots make great insulators.
Adding a 2nd thermostat sounds like a retrofit to fix the problem.
There should be a service note on how to do it, somewhere. My
guess(tm) is that two of the single thermostats will fit, if you can
find them.
Incidentally, on the exploded view of the fuser, there's an
thermistor-NTC which is what probably controls the temperature.
Yes, I think I offered / suggested such elsewhere (but didn't know if
it was just to provide feedback to the controller board to say 'Warmed
up'?
I'm sure it goes to the laser engine controller or power supply.
That's the way it's usually done on printers that I'm more familiar
with, such as HP.
I've not experienced them till now (normally HPLJ here and still have
a trusty P2015dn on our LAN)
Retch. The P2015dn and similar printers are my worst nightmare. There
are YouTube videos on how to replace the fuser that should give you a
clue as to how difficult and time consuming that series of printers
are to repair. I have three of that series printers that are on the
shelf awaiting repair of the formatter board, which suffers from lousy
soldering:
https://www.youtube.com/watch?v=x1acw-7kMws
https://www.youtube.com/watch?v=F1q2lmoLUzc
Cheers and thanks again for all your help.
Good luck and I still don't like Samsung printers.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558