Clogged Canon print head

Grandad35

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PeterBJ said:
I wonder when Canon started using this technique? So what was the printer model, printhead type and ink cartridge family?
I believe that it was from a Pro9000 (MKI or MKII is unknown) and it is stamped "QY6-0076" (it uses CLI-8 carts). My i9900 uses a QY6-0055 (and BCI-6 carts), which is said to be interchangeable with the QY6-0076-000. The QY6-0076 worked in my i9900 with BCI-6 carts with no problems. It is possible that the -0076 has one reversed screw but that the -0055 does not.
 

Grandad35

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Over the past two days I noticed light banding on areas with darker print. The nozzle checks always looked good and the carts tested properly for ink flow. Replacing the carts made no difference, so the symptoms pointed to a clog in the print head body.

Blowing alcohol through each ink pickup showed severe clogs in both the PC and Red channels. Disassembling the print head confirmed that the clogs were in the body, with the nozzle plate being clear. A little work with a syringe, alcohol and a short piece of tubing cleaned the channels (and all of the others while the head was apart). The entire procedure took about 30 minutes.

BTW - the screw on the left (looking at the print head with the circuit board facing down) was a left-hand screw.

This is the 3rd head that I have saved with this technique.
 

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How do you find out if a screw is left-hand without making it tighter?
 

Grandad35

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How do you find out if a screw is left-hand without making it tighter?
Fortunately, they weren't all that tight, and it wasn't all that hard by using a light touch. Without the knowledge that one screw may be the opposite hand, you would probably strip the head like I did the first time that I encountered this. The reason that the left screw was identified as left-handed is that it allows you to remove the right screw first (assuming that the right screws will always be right handed) to get a feel for how much torque is required before tackling the left screw.

To gain better control of the process of removing the screws, I use an appropriately sized screwdriver insert with a 1/4" drive flex handle with a 1/4" socket. This allows a very precise control of the rotation while making it easy to keep lots of pressure pushing the insert into the screw to prevent slippage.
 

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Wow, that's all brilliant!!!

It's nuggets of gold info like that post that can mean the difference between a very successful fix or making things worse!
 

stratman

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BTW - the screw on the left (looking at the print head with the circuit board facing down) was a left-hand screw.
I was just talking about this phenomenon of left-handed screws Canon printers. Why is it there? Are there rotational forces on that screw but not the others?
 

Grandad35

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I was just talking about this phenomenon of left-handed screws Canon printers. Why is it there? Are there rotational forces on that screw but not the others?
Perhaps it balances the forces on the print head when the screws are installed by an automated assembly device and gives a more reliable assembly procedure? If you like like conspiracy theories, perhaps they do it to discourage people from taking the print heads apart? I don't see an operational advantage from the left hand screw.
 

PeterBJ

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Maybe torque reactions cancel when the screws are installed simultaneously? Torque reactions might affect the nozzle plate alignment, I think.
 

stratman

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If you like like conspiracy theories, perhaps they do it to discourage people from taking the print heads apart?
Nope. Don't do conspiracies. The logistics and costs to have both left and right-handed screws used in the assembly would hardly be justifiable to prevent end users from tinkering with printers. But I do like your balanced force during assembly theory.
 

The Hat

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I have taken a few heads off in my time but never came across any L/hand screws ! :oops:
 
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