It’s very hard to beat color laser A3-format duplex printer for engineering needs for the printing tasks and hard-copies and documentation. I was fortunate enough to acquire open box HP Enterprise Color LaserJet , Model M751dn for good price four years ago. This model capable of duplex printing resolution at 1200×1200 dpi is current and still available for pretty serious money today. Other competitors are Kyocera P8060cdn, Lexmark CS943de and Xerox VersaLink C8000DT.

HPE M751dn is a heavy 45kg beast of a printer capable of outputting 41 pages per minute arrived in heavy box in May 2020 and was used at xDevs labs for all printing needs.

Printer came with factory original cartridges that had only 30 prints on counter, so essentially it was brand new. Unlike many desktop baby printers that come with “demo” or “starter” cartridges without much toner this HPE printer had standard set of cartridges in it. Supplies that these printers use are:

• One HP 658A W2000A : ~7000 pages black toner cartridge, about $190 USD/pcs
• One HP 658A W2001A : ~6000 pages cyan toner cartridge, about $290 USD/pcs
• One HP 658A W2002A : ~6000 pages yellow toner cartridge, about $290 USD/pcs
• One HP 658A W2003A : ~6000 pages magenta toner cartridge, about $290 USD/pcs
• Four HP 660A W2004A : Drum unit, one per each color. Good for ~65000 pages, about $274 USD/pcs or $1096 per set
• HP 3WT89A : Transfer kit unit, good for 150k pages, $417 USD/pcs
• HP 3WT87A : Oven fuser kit unit, good for 150k pages, $291 USD/pcs
• HP 3WT90A : Used toner collection unit, $25 USD/pcs

Alternatively printer can accept high-yield cartidge models designed for heavy use applications with much more toner in them. Their part numbers are same but with “X” letter instead of “A”.

• One HP 658X W2000X : ~33000 pages black toner cartridge, about $513 USD/pcs
• One HP 658X W2001X : ~33000 pages cyan toner cartridge, about $893 USD/pcs
• One HP 658X W2002X : ~33000 pages yellow toner cartridge, about $893 USD/pcs
• One HP 658X W2003X : ~33000 pages magenta toner cartridge, about $893 USD/pcs

As one can see supplies for these printers are pretty expensive since they are designed for heavy office workloads with monthly duty cycle up to 150000 pages. This is not your typical home printer :). Anyway, I’ve enjoyed this printer, large A3 format color prints and schematics for good four years until finally cartidges went to “medium” then “low” and now “very low” on toner level.

No surprise that black was the one that went empty first and caused grey prints in early November 2024. According to counters I’ve got about 4500 prints done. All HPE 658 series cartidges have small electronic chip designed to report cartridge information to printer and count pages/toner “level”. So far printer works even with level reported as “very low”, so perhaps it prints regardless what chip reports?

Spending $1k on cartridges set to replace all at once was not very interesting, so let’s investigate a bit what can be done to cheat the wallet a little?

I’ve ordered one black and one magenta open box original HPE 658A from a local seller but they arrived leaking toner all over. It was surprising that delivery postman even bothered to deliver as toner was literally coming out of the box corners, making huge mess. Arrived cartridges were damaged and toner was coming out of gaps between toner pickup roller and plastic scraper. Magenta roller had also physical damage causing big blob on each print due to application of excessive toner.

Installing wrong type cartridge (for example magenta into black position) upsets printer and it refuses to print anything until issue is resolved. Taking some transparent images on right side of the cartidge helpful to investigate the inner assembly.

Internal volume is just a tank with toner, no any magical bits or mechanisms in there it seems.

Looks like just three screws holding things together. Perhaps we can find a fill port in there?

First perhaps the easy part – replace damaged toner pickup roller and see if that fix issue with magenta color. You can see little proprietary chip with only two pads available.

Original cartridge is on the left, received on the right.

Removal of one screw let us remove the drive mechanism “cover”.

Now plastic gear thing can be removed off the inner sponge roller and we also get access to two more screws.

Removal of those screws reveals the end section of the cartridge body itself. And viola, we see translucent fill port cap. It’s glued shut to the body but possible to pry out.

For magneta cartidge I’ve left the cap intact and only replaced the outer soft roller from the original cartridge. Reassembled cartridge back in and that was it for magenta color.

Time to do the same for black but instead of replacing roller I’ve just shaked all the toner remains on the large paper newspaper and shoved it all back into old empty original cartridge.

I’ve superglued the plastic cap back in place. I don’t plan to refill this cartridge again, but it was quite interesting to investigate these cartridges a little. After reinstalling both cartridges into M751dn it started printing happy colorful pages again.