Drum compatibility for HP 2840

Yes, C9704a's drum and blade can be use in C3964A but not the whole set of C9704A, just the drum and blade. You can exchange them.

You can swap the left end plates between the drum units. There is a cut out that keeps the 9704 drum from seating into the machine. I think that you must also swap the chip as I believe that the chips are dedicated.

Sensational, thanks for that, got a Genuine HP C9704a Drum today for peanuts and it works a charm, easy fix, these drums are cheap to pick up, no doubt due to being older stock to some extent. Thanks again :)

Did you have to change the chip also or did the machine accept the new drum with the C9704 chip?

Hi,

I know this is some years old but my HP2550n is still working perfectly. But I bought a new imaging drum cheap off an auction site but was sent a C9704A instead of a Q3964A. Researched the web to find that only a plastic side panel is different, having a cut out shape. So swapped them over and it fits perfectly. However, I cannot get the reset to work. I have a Service Manual which says:

"Service mode functions

Cold reset
A cold reset sets most, but not all, default variables stored in NVRAM back to factory default
values. For example, It typically does not reset the page count, paper tray sizes, localization
language, or formatter number. To reset all variables, see "NVRAM initializer" on page 209.
To perform a cold reset
1 Turn the printer off.
2 Press and hold down the GO button.
3 Turn the printer on and continue to hold the GO button
4 After the Go, Attention, and Ready LEDs turn on, continue holding the GO button for
approximately five seconds, but not longer than fifteen seconds. During this process, the
Attention LED will turn off.
5 Release the GO button.
Note If either the Go or Ready LED turned off or no LEDs turned off before the GO button was released,
then repeat steps 1 through 5.
6 The printer LEDs will begin cycling from front to back. The cold-reset process runs until the
printer is in the Ready state.

NVRAM initializer
NVRAM initializer sets all default variables stored in NVRAM back to factory default values or to
a default ROM value, depending on the variable. It also performs a system reset.
NVRAM initializer resets the following:
� all menu settings to factory default values
� factory settings such as formatter number, page counts, factory paper settings
To perform a NVRAM init
1 Turn the printer off.
2 Press and hold the GO button.
3 Turn the printer on and continue to hold the GO button.
4 After the Go, Ready, and Attention LEDs turn on, continue holding for at least 20 seconds.
During this process, the Attention, Ready, and Go LEDs will each turn off.
5 Release the GO button.
6 The device LEDs will begin cycling from front to back. The NVRAM-init process runs until the
printer is in the Ready state."

I've tried it with the new chip in but maybe the drums are chip specific. So I put my old chip on the new drum and still no joy.

Anyone else succeed and, if so, how please?

Mervyn