Photocopier - paper scratches on the OPC

ok

rather

sticky

are

the

the

time

to

AC

I should have said the voltage on the centre of the revolving magnet developer drum , not to the OPC, the retraction voltage ? The votage that means the toner powder on the OPC that has become discharged from the exposure light is pulled off, back to the toner supply side, leaving the latent image. These fine line toner deposits are adhering more than the 250V "retraction voltage ?" will pull off but will pull off with the 7.3KV transfer voltage to the paper.

Anyone know of a source of plain carbon black, fine ground, without silicone oil/surfactants added , to dilute the supposed proper toner.

In that are is what looked like an afterthougt 1W resistor to ground, marked brown black brown. Surely not if a few hundred volts there. With a good light brought into the area I could then see it is brown black purple. Just an ordinary looking MO resistor, enamelled ,no glass encapsulation, but

1 Gigohm.

purple.

but

Wouldn't that be 100M? (10 x 10^7)

"William Sommerwerck" wrote in news:h0tplb$8p2$ snipped-for-privacy@news.eternal-september.org:

yes.

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Jim Yanik
jyanik
at
kua.net

I'm not used to seing that colour combination. Measured about 1000Meg, by comparison with a glass cased 1Gohm , with a high voltage source, it is grey not purple on the third band on rechecking.

"N_Cook" wrote in news:h0tvap$s24$ snipped-for-privacy@news.eternal-september.org:

I'm surprised it would stay 1G for any length of time,with an enamel coating.

maybe you could post a pic of it.I wonder who makes them?

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Jim Yanik
jyanik
at
kua.net

Its just a light blue bodied resistor that looks like any other except for an unusual colour code. It must be there to discharge any accumulated charge inside the developer chamber. A resistor with a crimp eye terminal at either end, looking a bit afterthoughtish. Whether it is 500M or 2000Meg probably does not matter. I imagine it could be difficult to make a high resistivity spiral of metal oxide, from my own attempts at making resistive compound for

1 meg pot tracks, very patchy resistivity

As for main thread I got into the generator circuit and temporarily upped the retract ? voltage up to 350V , for a test. Black lines still there and I think the image intensty was reduced as well, ie wanted charged, latent image bits, partially retracted back to the developer, so no solution there.

Apparently, from an industrial chemist, it is possible to get fine ground pure carbon black from chemical supply companies for some sort of filters , not activated charcoal. All laser and copier toner these days have silicone oil added , perhaps to avoid the use of silicone oil bath/wicks at the output fuser stage. Enough oil carries through to the output to keep the paper from sticking to the supposed non-stick finish of the fuser roller or its pressure roller.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

It's perfectly normal for the OPC to have mild scratches on it. As long as it's not down to the metal. (Which will give you white lines along the print.)

That's more likely to be due to dirt on the laser window. Give it a wipe & a blow. A stray hair stuck in there, or in the laser window of the cartridge will give you a line down the page.

There's nothing 'sticky' about the toner. It adheres to the drum from electrostatic attraction only. If it's sticking to the drum when it shouldn't be, there's something wrong with the HV, or the IR laser or cleaning light is not wiping the charge from the drum as it should.

Dry toner is *never* 'oily'. It's micron-sized particles.

'B' = Bias.

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    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
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*NO!* That is NOT correct! Laser/copier toner is totally dry. The silicon oil is applied to the fuser roller by a wiper pad, & serves to prevent the 'cooked' toner on the paper from sticking to the fuser roller as it exits the fuser assembly.

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    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

drum

only

hold

rather

sticky

are

the

the

time

decanting to

what

and AC

This is a conventional copier, not scanner/laser. Silicone oil wick/baths at the output have not been used on photocopiers since the days of sliding top ones, relying on silicones added (sub 1 percent) to the toner instead, not enough to appear oily to the touch but enough to make sure paper does not stick to fuser drum or silicone rubber pressure roller. The first one I came across to fix, was wet process toner in paraffin carrier, 1970s vintage, paper on a roll and a vicious guillotine.

The toner these days is mainly carbon/charcoal black but also such as styrene ,styrene acrylic copolymer, polypropylene,metal complex dyes, methylmethacrylate,styrene butylarylate, silicones and oleic acid

"N_Cook" wrote in news:h0vmaf$icn$ snipped-for-privacy@news.eternal-september.org:

toner is a wax compound.waxes are also lubricants.

--
Jim Yanik
jyanik
at
kua.net

On 6/13/2009 5:42 AM Jim Yanik spake thus:

That's not my understanding: from what I've read, toner is basically a mixture of pigment (carbon black or equivalent) and plastic (styrene) that melts onto the printed substrate (paper).

Maybe you're thinking of phase-change/sublimation printing (e.g., Xerox/Tektronix Phaser), which does use wax as the carrier.

--
Found--the gene that causes belief in genetic determinism

I would agree with that summary but add that there are surfactants added to assist in even distribution of the toner over the OPC, otherwise the coarse distribution of the iron filings transfer process would be rather patchy.

"N_Cook" wrote in news:h116cm$nn1$ snipped-for-privacy@news.eternal-september.org:

Heh.I worked for TEK for 21.5 years. their thermal wax process is a sort of wax-jet deposition thru a printhead. I've had pretty good looks at TEK's printer mechanics.

just feel the toner that's fused onto the paper;it feels waxy. Googling showed several references to wax for copier toner.

Isn't it done by electrostatics?

--
Jim Yanik
jyanik
at
kua.net

Correct.

That'd be my guess too.

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    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

printhead.

The rotating magnets + iron filings bring the toner close to the OPC and then the electrostatic voltage on the OPC, set up by the corona wire, pulls the toner across the gap. Then there should be an even charge distribution, but although very fine ground, it is finite size and the surfactants can help to allow easier flow. This maybe the key to the problem . What is the charge distribution over a semiconductor surface that instead of being perfectly smooth, has very fine scratches around it ? Maybe it is possible to reduce the corona voltage. Previously mistyped as 7.3KV, actually 8.3KV, I've not looked into that area, separate HV board somewhere, just measured the voltage at the corona housing .

I found the neat little Murata corona generator, marked 4.55KV, 0.3mA . I don't know what the o/p voltage should be Corona measured as 8.7KV so something not right there, plenty of room to drop the corona voltage. Not got to the point of monitoring the lines to it yet nor tried the preset yet, lines to it are 2 grounds, supply, control, and one marked REM , any ideas what that one means ?

Modern laser printers & copiers use monocomponent toner, which has the magnetic material in each toner particle. You're thinking of older systems, which used a separate magnetic 'developer' powder to carry the toner to the drum.

--
    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

On 6/14/2009 7:49 PM Bob Larter spake thus:

Reminds me of the old Kodak* copier I had when I owned a print shop; the previous owner had bought it for something ridiculous like less than $1000. The thing was a behemoth, and required lots of maintenance, but when it was running it would whip out good copies all day long and not even breathe hard.

I remember having to replace various parts of the "developer" system in it. Very old school.

• Actually Kodak/Heidelberg, during their short partnership in imaging systems.

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Found--the gene that causes belief in genetic determinism