Homebrew PCBs

On Sat, 02 Jul 2005 12:45:44 +0200, Philip Pemberton  
<philpem@...> wrote:

>
> You can say that again.. Four screws, then it lifts up and out. Very  
> nice.
> Check the continuity between the pins on the lamp connector before you  
> buy
> one though - replacing the thermofuse is very difficult, if not  
> impossible.
> It's even worse if the fuser lamp's burned out.

I don't consider the thermofuse a problem, the LJIII has thermoswitch  
though, which i have replaced on mine once (kapton tape rubbed through).  
Also, i think for PCBs it would be acceptable to bridge the thermofuse.  
Lamp must be good tho.

> No - there's an optosensor; the triac is in the AC Power Unit (the thing
> that takes the mains inlet connector). ISTR there's a 24V drive circuit  
> for
> the erase lamps, but that's it.

I see. Yes, now i remember seeing the triac in the AC PU when repairing a  
power problem.
Just remembered a small PCB on the fuser and thought it might be.

>
>> I guess you would
>> need to get one of the gears out of the printer too, or find some other
>> way to drive it. I don't remember if it is easy to modify for thicker
>> material.

> It isn't too hard. Remove the front paper guide (2 screws)

Really? Then i must have done something wrong - work on the front always  
required me to take of about 15 screws (the whole front "panel" thing),  
even for getting out the DC PSU. I thought that is the more nasty section  
of the printer. Maybe i missed a easy way to do it.
But still - how many of todays printers still work if you remove ALL  
plastic and a good deal of steel? If you take off a side-panel on a new  
printer the unit usually falls apart into a thousand pieces.

> and the flip-down
> guide at the back (2 more screws). The silver roller is the heated  
> roller,
> the red one is a rubber pressure roller. The big problem is that the  
> fuser
> feeds REALLY thick stuff (e.g. PCBs) at an angle of about 30 degrees,  
> which
> means the fuser needs mounting at an angle. I'll see if it does the same
> thing with 0.8mm laminate in a bit, or if feeding from the back makes any
> difference.

Maybe you can remove some guard? why is it feeding at such an odd angle.
(it sounds almost as if it is a sick animal..... ;-)

> I need to glue a bit of the plastic on my fuser back together though - I
> slipped and broke one of the mounting arms that holds the AC power  
> connector.
> Next job is to gut the AC power module and pray that the triac and
> zero-crossing optotriac are intact.
> Next job is to find a motor. Something that'll run the fuser so that the
> board gets fed in at about 0.1ips.

Chicken grill motor ;-)

>
>> I'm running my fuser at 160C.
> Exactly the same as the HP recommended temperature then. ISTR the LJ3
> increases the fuser temp to 180C when it's working on thick media and the
> thermofuse trips at 210C.

My PCB fuser is from a ricoh copier, and it had "thermal cutoff 160\ufffdC"  
written on top, so that's what i used.
The copier fusers often have a knob on the lower roller, which you can  
turn by hand to remove a jam. Neat to override the drive motor. I don't  
think i will ever use the LJIIID fuser for PCBs, 'cause that beast just  
isn't going to die any time soon.

ST