Cracked Open: Inside The HP 940 (C4902A) Ink Cartridge

Inside the HP 940 black ink tank cartridge.

Retail price of the HP 940 standard capacity ink cartridge.

Not a good buy - Check the HP 940XL - 3x's the amount of ink.

First off – look at this cartridge all you want, but buy the HP 940XL black – same cartridge, but “full” of ink.

The 940 cartridge from Hewlett  Packard (HP) comes in two different flavors.  The half-full 940 black ink tank, and the “full” HP 940XL black ink tank.  The 940 cartridges contain a very low amount of ink (22ml black – 10ml color) when compared to the 940XL which is completely full and contains a whopping 49ml of ink (16ml XL colors).

The HP 940 (which would include the entire 940 and 940XL series inkjet print cartridges for that matter), cartridge is not refillable (at least *we* do not see how it can be refilled).  There is a foil pouch inside the cartridge that compresses as the ink is used, and there is no obvious way to refill the cartridge.

This cartridge could also be called an ink tank, because that is exactly what it is – an ink holder.  There is no “revolutionary” technology on the cartridge, it simply holds ink.  The 940 series are basically the exact same cartridge design as the HP 88 series.

HP 940 – Black 22ml (1k pages)  $25.99

HP 940XL – Black 49ml (2.2k pages) $35.99*

*Can be had for less.  Much better cost per page rates with the XL cartridge.

Different type of HP cartridge – the ink tank:

HP 940 and HP 60 ink cartridges compared side by side 940 vs 60 print inks

These cartridges contain about the same amount of ink (940 16ml, 60xl 18ml est.)

The HP 940 series cartridges will only work in a select few printers, and consider yourself lucky if you own an HP (Hewlett Packard) Officejet 8000, or 8500.  You will still pay a premium for cartridges, however there are worse printers on the market – watch out on the ink.  As mentioned above, always get the XL black cartridge – a much better value.

The HP 940 is basically an ink tank.  There is no printhead on the cartridge (those are tucked inside the printer and must be replaced at about 10k pages print head).  Recently we have seen a few postings around the web discussing defective print heads – no matter the ink (HP original or compatible cartridges)  – so count on the print heads going out at least once.  They retail for $60.00 each ($120.00 total) so if you see them for less, pick some up.

Since all the hard work is done inside the printer – by the print heads – this cartridge is good at what it does, holding ink. The cartridge is entertaining to see dis-assembled for all of the engineering on the cartridge that is directed at making simple refilling impossible.

Simple Refill – Prevention:

Refill prevention is built into the cartridge with two distinct techniques.  One, a non resettable chip prevents “simple” re-use of the cartridge.  Currently there are no (none, zero, nada) HP 940 chip resetters on the market, so the chip cannot be reset.  Use of an “expired” chip in the printer is ok, and the cartridge will still function in the printer, however the ink levels will always be shown as empty.

Bottom side of the HP 940, 940XL, XL inkjet print cartridge - ink tank.

The chip can be moved to a full cartridge

Not easy – you need an xact-o knife, or something very sharp.  Do *not* mess around with a screwdriver as it will damage the chip.  If the chip becomes damaged it will no longer be recognized by the printer, and thus useless.  The chip on the HP 940 series looks identical to that of the HP 564 series we looked at here.

HP 940 back ink cartridge close-up of chip to be removed for use on chipless compatible

Chip is in there very tight. Use sharp and thin tool to remove.

Removing the bottom cover on the HP 940 Officejet Pro 8000, 8500 ink cartridge.

Removing the plastic cover from the bottom of the cartridge is easy enough – just cut the label where it covers the obvious seams – grasp with a firm hand, and it pops right off.  The internals of the cartridge can be removed (none of this helps to be able to refill the cartridge) – press the two tabs in, and the cartridge assembly slides right out.

HP 940 series black ink cartridge internal structure.  Internal parts on the HP 940 un-refillable ink cartridge.

HP 940 series black ink cartridge internal structure. Internal parts on the HP 940 un-refillable ink cartridge. Tabs.

Removing the cartridge assembly:

Internal ink container for the HP 940 series black inkjet print cartridge from Hewlett Packard.

All that is left is an empty shell.

Once the ink assembly has been removed, all that is left is the empty carcass of the HP 940 black ink cartridge.

HP 940 black ink cartridge empty shell.

HP 940 black ink cartridge empty shell.

Inside the HP 940 ink cartridge.

This cartridge is empty, all the ink has been sucked out of the internal pouch. the cartridge looks pressurized as the plastic covering has collapsed around the empty pouch.  The Black HP 940 cartridge contains 16ml of ink.  In contrast, the HP 940XL cartridge (same size and shape as this cartridge) contains 49ml of ink.

The cartridge could possibly be re-filled through the black ink exit hole (self sealing) with a needle and syringe, however not sure of the gauge required, and it would (maybe) be easy to puncture the internal bladder.

HP 940 black ink cartridge internal structure of the cartridge - can this 940 black ink cartridge be refilled?

HP 940 black ink cartridge internal structure of the cartridge - can this 940 black ink cartridge be refilled?

Cartridge not (easily) refillable…

We guess you could stick a refill needle where the ink exits the cartridge – self sealing access.

Inside the foil package there is a black pouch.  The foil like plastic is stuck to the black pouch with a very sticky backing.  It was very hard to get the two layers apart. Not really necessary to do this, however it is interesting to see that the pouch is “double sealed.”

HP 940 black ink cartridge internal structure foil pouch covers internal black pouch.

Cartridge Specifications (

Page yield information about this cartridge series:

Since the 940XL black cartridge is a better choice click here to, compare prices on the HP 940XL ink cartridges.