davewi11

asked Apr 1, 2015 at 6:55am
Hp HP LaserJet 5MP

Laserjet 6P fuser temperature adjustment

I have an HP 6P which prints well except the print can be rubbed off slightly if rubbed by hand. I also have a 5MP printer which works perfectly. I measured the resistance of the heater and thermistor contacts in both machines, and they seem similar. Thinking that the 6P heater might be faulty, I managed to swap the actual heater/thermistor strip between the two machines (the whole fusing assemblies are not interchangeable). It made no difference - the 6P still smears and the 5MP doesn't.

Surely there must be an adjustment to set the temperature? Perhaps it's in software only known to HP, or maybe a resistor on the control board could be changed. Does anyone know?
Bad Fusing can be caused by low fusing Temperature or bad Toner.
You may try to clean the Thermistor's Surface, if it is one of those which are in direct contact to the Fuser Hot Roll.

Since you did not write if you're using HP Original Supplies, you should first replace a Non-HP-Cartridge if you are using one.

And check for the Number of Pages printed. If the Page Counter shows 80.000 ore more, the Surface of the Hot Roll might have degraded. In that Case you could replace the Fuser Film Assembly.

As far as I recall, there is no Setting for the Fusing Temperature in these Printers; but I am not a real 6P-Specialist. They are all long gone now ...

Andreas
by Andreas E on Apr 2, 2015 at 5:40am Add comment
The fusing element and thermistor are thin films on a ceramic strip. A loose thin flexible plastic sleeve separates the strip from the paper, which is pressed down by a rubber roller. I hear that high temperature grease should be smeared over the element, but there is no trace of this - maybe that's the problem. I don't know what you mean by hot roll.

Both cartridges I tried have original HP labels on them. The page counter is ridiculously high at 300,000 - davewi11
There is no setting. I think the termistor on the fuser monitors the temp for the dc controller.
by dmzcompute on Apr 2, 2015 at 8:16pm Add comment
You do need a high temp grease on the element. If that's the original fuser with 300,000 copies I would recommend replacement. I've replaced lots of them on that model with nowhere near that many copies.
by moe on Apr 5, 2015 at 10:07am Add comment
To complete the story, my printer is now OK. Yes it was the lack of grease that was the problem. I found quite a bit had found its way under the heating element, so I scooped it up and spread it on the top surface. I guess the grease conducts the heat without a layer of air. I think I may need to add far more grease as it may get wiped off the top with the movement of the flexible sleeve. The grease seems like the silicon grease used with transistor heatsinks so I will try that.
by davewi11 on Apr 10, 2015 at 2:24pm Add comment
The grease you need costs about $10 oz. It has to both transfer the heat and lubricate the sleeve. If you put too much, the heat won't transfer properly as the grease will absorb it. You'll probably ruin it with your experimenting.
by moe on Apr 10, 2015 at 4:33pm Add comment
Thanks for the warning about the grease. I was thinking of adding grease over the entire surface of the metal holder, not the actual element, so that as the sleeve moves there should always be some grease ending up on the element. - davewi11