Why is my printer printing blank pages?
Fix blank page printing ink seems ok. Local print from panel buttons same. Possible circuit board?
The HP 842c was introduced in 2000. Like most old printers, the cartridges are large and last. Along with this, it is also more reliable than modern inkjet printers. While the ink lasts, the printer uses a Tri-Color cartridge. If one color is empty, the whole cartridge is considered empty.
If it goes through the motions, feeding paper and running the print head back and forth over the paper, the circuit board is almost certainly ok. Why do you think the ink is ok? That seems the most likely cause even if the printer is reporting to your computer that it has plenty of ink.
These older HP printers generally have cartridges with built-in print heads. These have the great advantage that if the nozzles get blocked (as they do with a period of disuse) then you get new nozzles with new cartridges.
Unlikely, but there’s a flexible ribbon which connects the print head to the main circuit board, folded in a “U” to allow the print head to move back and forth. If that had got broken or damaged then it wouldn’t print, though the ribbon is tucked away inside and unlikely to come to harm unless someone was deliberately poking around inside. The other thing to check is the gold contacts on the back of the cartridges, and the corresponding contacts in the cartridge holder, if they had got dirty, perhaps with ink on them, but if that was the problem it’d be surprising if both colour and back were affected in the same way.