Canon MP630 magenta printing only on one half of printhead

[Ink stained Fingers]

I don't know whether the current service manuals still contain circuit diagrams to that detail showing all the many connections from the nozzles for the conductive elements to the driver/multiplexer chip. The connector pad of the printhead by far does not have as many contact fields as there are nozzles. There is a chip doing the decoding, the nozzle resistors are arranged in a matrix, a line gets connected to the driver voltage - something like 24 to 28 Volt as I remember, and a column gets connected to ground at the same time - for a few microseconds and the nozzle resistor at the crossing point gets active, boils the ink etc. So this chip does not just logic functions but as well power functions switching the voltage to the resistors on and off. So each nozzle resistor has a binary address, but those numbers may not all be consecutive but in groups - by color - by droplet size - physical location in the printhead etc. And it's the matter of the driver/firmware to address the correct nozzles at the right time. And if a particular area in the chip is defunct you get those patterns - half of the color pattern missing or alternating sections missing in the paper black section or worse with smoke coming out of the printhead or other error conditions. It's all not repairable and cannot be cleaned away. Smoke - B200 error etc happen suddenly other than individual nozzles giving up and not printing anymore.

 

[The Hat]

I’ll leave you two guys to explain it better, because you’ve lost me with this technical jargon, all I know is that part of the magenta nozzles have left the building...

 

[stratman]

And if a particular area in the chip is defunct you get those patterns - half of the color pattern missing or alternating sections missing in the paper black section or worse with smoke coming out of the printhead or other error conditions.

To clarify, you also agree the nozzles are not necessarily burned out when the OP's pattern occurs? It is something upstream of the nozzles - the chip, as you put it - that causes the pattern.

We might say the nozzles are burned out as shorthand or ease of explaining.

 

[The Hat]

We might say the nozzles are burned out as shorthand or ease of explaining.

It’s not the nozzles that are burned out, more likely its the electronic bits back stage that have gone up the swanee...

 

[Ink stained Fingers]

that's the beauty and fun with the Canon printheads - there are several failure modes - some which let you clean and clean and... or a B200 error ... or smoke or a problem on the motherboard and don't forget the ink which might clog and dry ... and the user fiddling around with non fitting cartridges or air inhibiting the ink flow or ....chips getting rejected and yes - those resistors - heating elements - in each nozzle may fail individually or the chip in the printhead assembly or the contacts between the printhead and the carriage , a printhead is that complex that you can get all this ...
I just can recommmend in this situation to get a working printhead - or consider a replacement of the printer by a newer model - and to reconsider which options are needed, nice to have or necessary like connectivity - duplex - overall print volume and type of prints, ease of refill and some more.