Archived from groups: comp.periphs.printers (
More info?)
On 19-Mar-2005, Klaus Pieper <kfpieper@web.de> wrote:
> The manual indicates that this is a hardware issue, I found postings
> pointing in the direction of the fuser unit.
>
> How can I get more diagnosis? If the fuser is broken, where could I get
> a used one to replace it (living in Germany, Central Europe).
The fuser comprises a bulb and commonly an opto-coupler with
power triac to form a solid state switch. The opto coupler is
driven from a temperature sensing thermistor in the fuser assy,
via a measuring circuit and several safety switches.
You may have to cheat some mechanical cover interlocks,
peer into the paper exit, or do whatever is needed to see
at least one end of the fuser bulb, to see if it comes on
at switch on. It should, even if only for a few secs.
The fuser bulb is easily checked with a cheap multimeter.
It's usually in series with a bi-metal cutout as if it stayed on full,
It's typically 500W, under fault conditions you would have
a good bonfire. Don't know how accessible your bulb is.
If you can remove the fuser as an assy, you can put in a
60W or so domestic light bulb wired to the fuser lamp
connections. It should come on for a few secs. at
power up. Then it senses fuser (and the thermistor) not
heating up and goes out again.
I've just had to fix my fuser assy, or rather the driver.
A lot depends on how technical you are, there are
service take/apart manuals in PDF format online for
most of the HP lasersjets. I bought the parts, quite
cheap, rather than a replacement. You first have to
determine if it's the fuser or it's power supply.
Replacement modules are expensive if you pick the
wrong one at random and it doesn't fix the problem.
Modules are also hard to find outside the States.
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