Brother MFC 9420CN Color Laser Printer

Remove the pins. Do a factory reset.

That means the photodiode or whatever they are using to detect the presence of the opc belt is not being triggered. Could be toner on the sensor, or the release pins may be somehow preventing the detection.

Try reseting the OPC counter:

The procedure is at the end.

However, I don't think it will fix the problem. Some sensor (optical or microswitch) is not working when you insert the OPC belt cart. That sometimes happens when the wrong cart is crammed into the printer. Brother makes several that are similar. Verify the number. My guess(tm) is that there's a microswitch somewhere inside that activates when the OPC belt cart is inserted, and the connector at the end of its cable is unplugged from the last person that was inside the printer. Reading between the lines of your posting, it seems there was some previous work done.

Ooops. That won't work with the MFC 9420CN. It has a chip on the OPC cart. See:

for a replacement.

I still think it's a bad insertion sensor (microswitch) or cable connector.

Note that the chip is usually a PCB with a chip wire bonded or glued to the PCB and covered with epoxy. I destroyed one by pushing on the epoxy. They're quite fragile.

Already done.

'Factory reset?' I've reset the OPC counter, and checking the other counters(page, drum, fuser), they all appear to have been reset. Is there one I've missed?

PlainBill

My idea also. However, the presence of a microswitch is non-obvious, and there are no signs of optical sensors present. Or maybe I've been barking up the wrong tree. I've been thinking in terms of a detector that would be blocked by the cartridge. Perhaps a reflective sensor that detects the presence of a cartridge. Thanks, some good ideas.

PlainBill

Thanks,

I'll see if I can locate anything. You sugestion of an incorrect cartridge is also worth looking into.

PlainBill

Nope. Jeff suggested an incorrect cart. Might be worth investigating. I can put an HP4000N back together in my sleep but most of my dealings with clients who owned multi-function devices was that they leased these things and they were serviced by the lessor.