740 has ghosting and smeary images

[silicontundra]

Hi, have a 740 that used to work, but now has 3” ghosting repeats and smeary images only on the right side of page. Have replaced transfer kit with new and cleaned the paper feeder with IPA. Have cleaned electrical contacts and bent the tabs so that intimate contact is made with the transfer roller and paper roller tips. Have checked for loose wires and connectors in the electrical / electronic backside modules.

In my different tests this ghosting and smeary images originates with toner that remains on the black “conductive carbon foam” image transfer roller. I have seen, have cleaned off, and have seen more toner (especially magenta and yellow) build up on both the steel and black rollers. It appears that there is not enough “voltage bias” on these two conductive rollers so that the charged toner particles will completely transfer to the paper. The too low voltage bias which can’t build up is a possible reason that the right side of paper is the ghosting and smear side; not the left side which is closer to the voltage source.

This is not a fuser problem as the smeared images don’t scrape off with a fingernail. It appears that the toner smearing occurs where the transparent plastic shields wipe the toner buildup on the rollers.

Question: Is this due to a voltage bias problem associated with a power supply? What is the voltage spec that can be measured at the contacts? Or is this a problem because the voltage bias is being drain off somehow?

This ghosting and smearing occurred after solving a paper feed problem by cleaning the paper feed clutches with various cleaners including Goo-Gone cleaner, WD-40, silicone lubricant, and petroleum lubricant. Do these cleaner / lubricants affect the resistivity of the plastics / materials used in the paper feeder / image transfer kit assy?

TIA, Phil

 

[silicontundra]

Hi All,

I bought a Tek Phaser 740 Service Manual on eBay. There are a couple Sellers, but the one I got was from GovTechMedia for $12. It is not too bad, good for color laser theory and gives rough idea of where all the modules are and what they do. It does not go into real detail; not down to the part level and definitely doesn't cover fasteners with part#.

The manual says that there indeed is a voltage bias on the transfer kit roller. So I was right! there is positive 500-2400 volts on the "carbon sponge roller." The diagram shows that there is +400v on what I think is the stainless steel feed roller ;-)

This means that the silicone cleaners / lubricants that I used to clean the feed clutch are probably bleeding off the bias voltage through conductive residues on the black plastic feeder assy, looks like a phenolic.

The voltage bias contacts to the rollers are supposed to be lubed with a silicone conductive grease, p/n 006-7998-00. Anybody know the specs on this stuff? From cursory look at the web, can be carbon or silver filled. How about a source other than the Tek or Xerox service depot?

I'm going to try cleaning the plastic assys in Isopropyl alcohol, after looking at the active solvents in cleaners made by RawnAmerica.com , TechSpray.com, and LPS, stocked by our local electronics supplier. Anybody know about a cleaner specifically made for silicones? I hear it is really tenacious stuff.

Regards, Phil

 

[silicontundra]

Hi All,

Solved the ghosting problem! The printer is now working fine once again. Was able to repair the feeder assy using factory service manual that was on eBay. Disassembled and cleaned the feeder assy with removal of c-clips on shafts.

Actual solution was straightening the cam follower so that full pressure was made between both voltage biased st.st. paper feed roller and the transfer kit roller. The smeared image was simply due to not having enough pressure to physically transfer it to the paper.

FYI, I found that the service manual illustration was wrong on paper flow through these rollers and that the bias voltage specs were reversed... ;-)

Cleaned the black ABS plastic parts with a silicone cleaner from a local vendor, American Polywater. But conductive silicone grease and bias voltage wasn't the real issue.

Regards, Phil

 

[penybont]

I have a phaser 740. Just sorted out a couple of problems. Really need the manual. Anyone know where to get it in UK?
Seen the entry about ebay. No luck there.

 

[silicontundra]

From eBay Seller GovTechMedia listings, they ship their CDs worldwide.

 

[Shellbang]

All I can say is thankyou for this Fix.