Canon NP6621 - just wont copy !!

[Emjay]

Hi !

Not done any Canon machines before (mainly worked for KM dealers).

Got a Canon NP6621 which appears to be ready to copy, but just wont !

There are no error codes, the doc feeder is detecting paper size correctly (as it will off the glass as well).

The START key is lit green, but pressing it has no effect.

Before I dive in too deep, am I missing something very obvious here ?

One thing I haven't see yet is the scanner lamp illuminate. On older analogue machines, I would expect the lamp to come on briefly at power up. This machine does a quick scanner lamp shuffle but no light.

I should say that I don't know the history of this machine as it's one we've taken back whilst installing a new one. Looks like it has been sitting idle for a few months. I do have the service manual.

Any Canon experts out there ??

Thanks,

MJ

[teckat]

Check for a stuck key / button on control panel

those print keys on under side can crack off tab that hits small button switch on panel board/ remove and inspect panel

check scanner cable/ pull scanner all the way over/ replace glass/ turn on / report back

Control Panel
keys..JPG
any of these keys/if stuck will prevent copying
1. Removing the Control Panel
1) Remove the copyboard glass.
2) Remove the upper left cover.
3) Open the front door.
4) Pull the open/close lever, and open the body.
5) Remove the right cover.
6) Remove the left cover.
7) Remove the four screws , and remove the
inside cover
Remove the screw e, and disconnect the four
connectors r (J801, J802, J803, J804); then,
remove the control panel .

[zaza]

hello technician ..me l have the same problems in 2 np6621 it's so dificulte copiers ...but l found the problems ...it have broked selinoide of scanner ...

[D_L_P]

Good old NP's

I think Teckat made a good suggestion, those keys get stuck easy. Just keep pressing each key individually until you find one that doesn't feel right.

Couple things to check, I remember the heat sleeve on the lamp will slide over and cover the AE sensor. I can't remember if it caused the issue you have or an error code or just took a long time to make one copy.
If I remember right a bad lamp could cause it to turn itself off, or if just one end of the lamp was bad paper will feed to the registration and just wait indefinitely.
There was a tech pub about new style contacts for the lamp, but I can't remember any details other than they were just a better fit.

In case you want to check the lamp, it comes out the back. Take off the back cover and there's 1 screw on the endcap and you can pull the lamp out. GL

[blackcat4866]

DLP and Teckat are correct.
If a single button is stuck down no other button will work. Sometimes it's obvious, like one of the number keys, in which the display fills up with that number. Sometimes it's not so obvious, like a Clear key. Like DLP suggests, just one-by-one press each button, and listen for the click. You'll probably find one or more keys that don't click. It's usually just scurf. You know, the dead skin cells that all living things shed when they touch things. If all the buttons click , you may just have a failed push switch.

Disassemble the panel, and check the hinges of each button. With a toothbrush and some dish soap, clean the ridges around the edge each button and the holes throught the panel. If all of the buttons clicked for you, meter out each switch on the lowest resistance setting. You probably won't see infinite resistance while the switch is soldered to the board, but when pressed each switch should close to 0.2 ohms. The buttons that fail the most often are Start, Clear, & Tray Selection. There are three ways in which the switches can fail:
1) Cold solder joints to the PWB
2) Worn contacts within the switch (increased resistance when closed)
3) Cracked traces on the PWB
If you do not have a replacement switch, you can swap a less commonly used switch (like sort, or interrupt) to a more necessary location. Cold solder joints can be re-touched. Sometimes cracked traces can be repaired, but most often it's fatal.

That will cover most cases. =^..^=

[Emjay]

Thanks for the replies.

The problem did indeed turn out to be a number of defective tact switches (the small push buttons under the control panel). I replaced them with buttons from an old VCR timer control pcb (same dimensions and pin outs).

After cleaning all the mirrors, the copy quality is now better, but there is still a problem with it. I've scanned a copy so you can see what I mean.

There are a number of voids across the page. These are present regardless of which setting I put the exposure control in (ie lighter or darker).

NP6612..jpg

It's the same whether the copy is made off the glass, or via the DF. I'm sure this is something simple, but I'm not a child of the analogue copier era! :-(

Thanks in advance.

[teckat]

Hi !

Not done any Canon machines before (mainly worked for KM dealers).

Got a Canon NP6621 which appears to be ready to copy, but just wont !

There are no error codes, the doc feeder is detecting paper size correctly (as it will off the glass as well).

The START key is lit green, but pressing it has no effect.

Before I dive in too deep, am I missing something very obvious here ?

One thing I haven't see yet is the scanner lamp illuminate. On older analogue machines, I would expect the lamp to come on briefly at power up. This machine does a quick scanner lamp shuffle but no light.

I should say that I don't know the history of this machine as it's one we've taken back whilst installing a new one. Looks like it has been sitting idle for a few months. I do have the service manual.

Any Canon experts out there ??

Thanks,

MJ

check all keys on panel/ they should bounce back when touched
remove control panel/ check for a stuck key/ also on the underside of the Start Key -small tab may be broken off and not making contact with switch.

[teckat]

Thanks for the replies.

The problem did indeed turn out to be a number of defective tact switches (the small push buttons under the control panel). I replaced them with buttons from an old VCR timer control pcb (same dimensions and pin outs).

After cleaning all the mirrors, the copy quality is now better, but there is still a problem with it. I've scanned a copy so you can see what I mean.

There are a number of voids across the page. These are present regardless of which setting I put the exposure control in (ie lighter or darker).

[ATTACH=CONFIG]4871[/ATTACH]

It's the same whether the copy is made off the glass, or via the DF. I'm sure this is something simple, but I'm not a child of the analogue copier era! :-(

Thanks in advance.

How many copies on machine ????/ this model came out in 1998 !!
First Start with below:

Optical path= inspect n' clean

Primary
Charging Roller

Transfer
Roller

DRUM

Developing/Cleaning Assembly

[collme]

as teckat says start with optical path but may i add to clean off scan rails and re lube as slight scan judder can cause the effect your having and if machine has been idle as you suggest then previous oil/grease may have thickened up causing mirrir assys to jump a little.

[D_L_P]

Another thing about the developer assy. Pull it out and look at the cylinder to see if it is evenly coated with toner or has streaks. I remember cleaning out the developer and using a piece of paper or fine sandpaper to clean all the buildup off the doc blade.

[Emjay]

Thanks for all your suggestions about the image quality problem.

The machine has done 310K, which I reckon isn't overworked. The second counter (which I suspect is a PM counter?) is on 60K.

All the mirrors (6 of 'em) are spotless, the transfer roller has been dry wiped, primary charge roller has been cleaned. I've vac'd the waste toner out of the hopper on the drum assembly.

There are a lot of fine lines on the drum surface, which would account for the feint intermittent dark lines running in one direction, but not for voids.
The mag roller is getting evenly coated - the "brush" looks good in fact.

I never thought about the scan rails - they are next on my list. That may well account for the fact that every 5 of so pages, the voids are almost gone.

I think the drum is probably well past its best - its a light purple colour - probably not an genuine Canon part ?

Will let you know how I get on.

Thanks again.
MJ

[remielee]

Hi !

Not done any Canon machines before (mainly worked for KM dealers).

Got a Canon NP6621 which appears to be ready to copy, but just wont !

There are no error codes, the doc feeder is detecting paper size correctly (as it will off the glass as well).

The START key is lit green, but pressing it has no effect.

Before I dive in too deep, am I missing something very obvious here ?

One thing I haven't see yet is the scanner lamp illuminate. On older analogue machines, I would expect the lamp to come on briefly at power up. This machine does a quick scanner lamp shuffle but no light.

I should say that I don't know the history of this machine as it's one we've taken back whilst installing a new one. Looks like it has been sitting idle for a few months. I do have the service manual.

Any Canon experts out there ??

Thanks,

MJ

i think the problem is on the scanner section did you check the lamp if theres a continuity? the cables if was connected properly or if the scanner stock and dosent move check if it was freely moving on the railings

hope it will help you.

[Emjay]

Sigh! Back again for more help! Analogue copiers are just not my thing. :-(

I've checked all I can on this machine. The scanner rails are fine.

Most of the time, the copier produces copies with dark bands across (see pic below - example "A"),
the bands do tend to move around the page, so are not in the same place all the time. They also vary in
thickness from thin (around 4mm) to thick (around 10mm):

NP6612_A..jpg

and then every now and again, mixed in with the poor copies, is a really decent one (example "B") !

NP6612_B..jpg

For an old analogue copier, I reckon the example "B" is acceptable. But why does the machine only throw out a page this good every now and again?

I'm stumped !

[blackcat4866]

It looks to me like a drum ground issue. When the drum coating gets too thin you'll get the appearance of bars crossfeed. The distance between the bars stays the same, but the thickness of the bars can vary from nothing to very wide. =^..^=

[Brian8506]

If this is the same as a 6521 the drum will code out at 40k unless someone changed the drum chip. If that drums been in there a while it may need to be changed. Have you stopped the copier halfway thru the cycle to see what the image looks like on the drum? Is the primary charge roller getting dirty quick?