asked Apr 22, 2013 at 1:02pm
Hp HP Color LaserJet 2840

HP Laserjet 2840 fax line causes interference

Hello group, hope someone can offer some hints, suggestions, advice, etc.

This printer works great in all functions but faxing. As soon as you insert a telephone cord into the fax port you will get humming throughout every telephone in the house. Disconnect the fax line & all humming goes away. Tried another cord.

I assume people will tell me its a bad modem (fairly common?)

Can this be replaced? (I assume its some proprietary part from HP?). Pretty involved? I don't mind digging in if feasible.

I believe all of the fax functions are embedded on the formatter. replace formatter board, follow instructions in 2840 service manual.

If you know someone who is good with component-level troubleshooting and repair, and knows telephony circuits, they might be able to isolate the bad component on the formatter board, and replace it.
by eric111 on Apr 23, 2013 at 9:10am Add comment
just want to point out that the problem is not the fax "line" itself, but the printer circuit board's effect on the fax line, by way of failed components on the board. unplug fax cord from printer, everything is okay, and we are assuming the fax cord is good.

If not the above, the telephones in the house love that printer so much, it makes them hum with delight!

by eric111 on Apr 24, 2013 at 4:21pm Add comment