Another Canon Printhead Bites The Dust?

Why should you be worried about using more rather than less, no one ever measures how much they use washing their dishes, so if it’s safe to use the dishes afterwards then I reckon a hungry print head won’t mind one little bit either, anyway you can always relay your own fears by using less if you wish..

I have used 10ml failry 200ml distilled water in a sealed container, will keep it sealed for two weeks. April 02 we will see if it worked

I will open the container avery 2 days to make slight pumping action since I put the head on some window wash fiber cloth.

I have been using my Pro9000 II with its original print head as a 6 ink (red & green unused as red has gaps in its nozzle checks) printer. But I did a nozzle check the other day which looked OK until I noticed that PM was showing PG (light green), all the rest were OK except the faulty red. 4 or 5 nozzle checks later and PM was back to being PM.

So I decided it was time to replace the head with the new one I had purchased previously. This new head performed as it should. So the logic board is clearly OK.

I have taken the old head apart, carefully and been able to visually inspect and test water flow through individual parts to a degree that I am confident that there are no blockages and that the red channel failure was due to electrical failure, either in the on board IC or the red nozzle. It is possible to see daylight through the nozzle plate (i.e. from the ten slot holes in the back of the plate and out through nozzles) at various angles, sufficient to be sure all nozzles were clear.

The colour change in PM appears to have been leakage across the back of the nozzle plate. The multi holed plastic gasket in contact with the back of the nozzle plate appears to be OK, but I suspect that some leakage occurred at that point. However I must check the main plastic block for leakage between channels to be certain.

The fact that the aluminium heat sink plate rattled if the print head was shaken, indicates that the narrow, thin layer of applied adhesive, between the aluminium and the back of the nozzle plate, had become detached. This implies that the heat sink function would have been none existent.

I am hoping to reassemble the print head and continue to use it as a six ink head if it still works.

One point I forgot to mention was that one of the two screws holding the nozzle plate in position appears to have a reverse thread. I found one would not unscrew, so started to drill off the head and the drill dug in and out popped the whole screw! Very devious!

I have also found that one strip of nozzles does appear to have a small blockage, not noticed viewed in daylight, but if you hold the nozzle plate with the back of the plate to a domestic lamp bulb, the small slotted ink entry holes illuminate all the interior of the nozzle strips, allowing any easy check of the state of the nozzles. I must check to see if that is the red channel.

This raises the question of how much of each nozzle row actually generates the pulse of ink? Would a small blockage, not more than say 5% of the row length, cause the problem? I will take some photos of all the parts and of the blockage and post them later.

Be careful how you go Ian, because putting the reassembled print head back in can sometimes cause electrical failure in your logic board, but once the head is carefully realigned properly then there shouldn’t be any problems, but just be careful anyway !

I take your point Brian, why risk it! Well it turned out that the visible clog or clogs (one noticeable, the other very small) were in the PM nozzles and there was no cross leakage in the black plastic part.

Anyway here are some images of the bits.

Emulator said:

One point I forgot to mention was that one of the two screws holding the nozzle plate in position appears to have a reverse thread. I found one would not unscrew, so started to drill off the head and the drill dug in and out popped the whole screw! Very devious!

I have also found that one strip of nozzles does appear to have a small blockage, not noticed viewed in daylight, but if you hold the nozzle plate with the back of the plate to a domestic lamp bulb, the small slotted ink entry holes illuminate all the interior of the nozzle strips, allowing any easy check of the state of the nozzles. I must check to see if that is the red channel.

This raises the question of how much of each nozzle row actually generates the pulse of ink? Would a small blockage, not more than say 5% of the row length, cause the problem? I will take some photos of all the parts and of the blockage and post them later.

Click to expand...

Yes, some Canon print heads are assembled with both left hand and right hand screw threads...really sneaky!!

Emulator said:

...snip... I noticed that PM was showing PG (light green), all the rest were OK except the faulty red. 4 or 5 nozzle checks later and PM was back to being PM.... snip...

Click to expand...

Don't overlook the possibility of cross contamination caused by a high suction pressure on the red cart. Suppose that the PG cart allows a little extra ink to flow out onto the surface of the nozzle plate and that the PG ink flows over to the R nozzles. If the R cart has a suction on its exit port, the PG ink on the nozzle plate can be pulled back toward the R cart - that's why it can clear up so quickly with a little printing. I have had this happen to me twice in the past when my yellow got contaminated with some other color.

Grandad35 said:

Don't overlook the possibility of cross contamination caused by a high suction pressure on the red cart. I have had this happen to me twice in the past when my yellow got contaminated with some other color.

Click to expand...

Worst cliffhanger ever. Then what?

Hi Grandad35, yes highly likely, I suspect the ceramic plate to plastic gasket contact was poor, presumably due to shrinkage of the plastic.