RE printer carriage drive belt replacement

[Tim7520]

I took the HP 7520 printer apart to repair a missing cartridge error code and I took the geared drive belt for the printer head carriage off the drive motor. I randomly put it back on and now the carriage bangs on both sides real hard and loud as it races back and forth side to side. Does that belt have to be put on the same spot on the motor gear (like a timing belt) or is any spot O.K.? I took off the locator strip and put it back on in the same place so it should be fine.        Tim

[Valsimot]

Double-check the encoder strip (locator strip) if you didn't thread it through the sensor on the back side of the carriage you get banging.

[Tim7520]

Thanks for the suggestion. The encoder strip was not properly centered and after re-setting it centered it is now operating correctly but the "problem with the red cartridge" remains. I have cleaned the print head, cleaned the contacts, cleaned the circuit board under the print head, cleaned all cartridge contacts, replaced the red cartridge, and unplugged all ribbon cables, cleaned the ends and sockets and replaced them, all to no avail. Any ideas on what causes I might have missed for a red cartridge not being detected? I now have 3 red cartridges and none work.

[Valsimot]

It's impossible to know.
It could be a defective printhead ( most common) defective mainboard ( less most common) or an FFC connecting printhead to the mainboard.

[Tim7520]

Thanks for the suggestions. I am going to try unplugging the various ribbon cables to see if I can pin down a location. Next I will test the ribbon cables end to end. A wiggle of the 2 traveling ribbon cables seemed to resolve the issue briefly a few times but not any longer, so I suspect a broken conductor. Lastly I will check the circuit boards for bad solder joints. Really a poor design that shuts down all functions rendering the device completely useless because one color cartridge is not recognized. The machine would still be useful for B&W printing and copying, faxing, and scanning, and even some color printing without the red. Now, instead, it goes to a landfill after I chop it up with an axe and buy a Canon or Brother. HP should re-think the design perhaps. Way too much effort is put into ink cartridge security and monitoring.