Printer and Photocopier Troubleshooting and Repair Collection : Copy counter fuses                      
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Copy counter fuses

"I have a Panasonic KX-P4420 laser printer. It locked up with a message about 36K service.

I issued the incantation to reset this message. It now works again, but the display is flashing 'Change DEV' and 'Change Drum'. This makes it more difficult to use the menu system. I'd like to turn them off.

From the dealer's explanation, I gather that there are fuses in both the developer and the drum. When you install a new one, the machine senses the fuse, resets the counter then blows the fuse. If this is true, I should be able to bridge the fuses with another and reset the counters. Maybe even a resistor will do it. Or maybe even a reset switch somewhere?

Can anyone tell me how to reset the error messages for the developer and the drum? I'm willing to disassemble the thing to do this."

(From: Jeff Roberts ( jroberts@axionet.com).)

  • To turn off change drum message turn machine on while depressing "<" key

  • To turn off change dev message turn on machine while depressing "^" key

    (From: Mark Wilson (mawilson@worldnet.att.net).)

    There must be something additional to that. I tried it on my 4420 and it did not work. Can anyone shed additional light on this??

    (From: Jeff Wilkinson (laser@ix.netcom.com).)

    The fuse on the drum unit burns out when you first install it. This momentarily shorts the input to a counter IC and resets the counter. I would be very careful about shorting it with a piece of wire, even though the circuit is current limited it is just not a safe practice. Of course you could always replace the drum! The same is true for the developer unit. The developer and drum unit should have been replaced at both 18K and 36K pages as they have reached there useful life expectancy. E-mail me if you want more info, I believe I have the value of the fuse required here someplace.

    (From: Mark Wilson (mawilson@worldnet.att.net).)

    I believe there is a module with a microfuse, similar to the one on the toner cartridge. If this is so, you have to replace the microfuse (preferred) or short it with a piece of wire (not recommended). The fuse burns out after so many pages, triggering the drum message. When the drum is replaced, it has a new (intact) fuse.

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