Canon mx870 only printing alternate strips

John Baddeley

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Hi all, i've just joined after googling my problem led me to another post here. Please tell me if I don't 'behave'!
We've had our mx870 from new, feeding it 3rd party carts and it has been fine.
It's been in use most days.
Now it does not print alternate strips of black text (eg document sent from a windows PC). If I do a black copy of a good print [from a different printer, of course] it will come out complete.
To determine which ink is being used, I ran tap water over a corner of both the print and the copy. The black text on both stayed without running, but the title of the printed one, which is [correctly] printed in red, smeared. This seems to me to indicate that both pc printing in black and copying in black uses the pigment ink. (Yes?)
The printed strips are about 9mm high, and the blank ones about 5mm high on the page. They alternate, very regularly, all down an A4 page. The strips do not relate to the lines of text at all. The blank ones do actually have faint dots in the bottom 2 mm.
Following advice elsewhere here, I've done a nozzle check, which prints most of the grid of black rectangles [some missing, but ok for our text use] and the solid black bars either side of 'PGBK' but only as far as the bottom of those four letters - the rest is blank. (This is the same as the text printing, ie 9mm of good , 5mm of nothing).
The bottom edge of the printed strip is very well defined, not faded out.
All the colour stripes (& grey) are there and close on perfect.
If I tell Word to print the text in red, or grey, it comes out complete.
I have removed the printhead, cleaned the contact pad, and the contact pins with a cotton bud soaked in isopropyl alcohol. As that did no good, I removed it again and poured isopropyl alcohol over the large circular hole corresponding to the black cart, and repeated that flush twice. Then reinstalled the PH and did a deep clean. Still stripey!
Any ideas, please?
Many thanks
John
 

The Hat

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Hi @John Baddeley and welcome, the way your explaining your problem sounds like your PGBK nozzles are having problems outputting ink and may have already burned out.

A picture is worth a thousand words, so if you could upload a nozzle print for us to see, that would give a much better explanation as to what’s causing your problems, try not to use your printer for anything other than a nozzle check for the time being, and report back soon please...
 

PeterBJ

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This looks to me like the pigment black section of the print head has failed electronically. Could you upload a scan or photo of the nozzle check. Please also include a scan or photo of a text document, for instance Windows Printer Test Page, showing the striping.

When a Canon print head fails, there is a risk that it damages the logic board. A logic board damaged in this way might damage a new print head. So replacing the print head is a gamble and I cannot tell the odds for success.

The print head is QY6-0073 if you want to look for one. Beware of used print heads from the far East that have been cleaned to look like new and packaged in replica foil bags and cardboard boxes.
 

John Baddeley

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Thanks all for your responses. Particularly PeterbJ with the warning and the link. I'm in UK btw.
I'll try now to upload the nozzle check print.
Drat! The jpgs generated by my MG5350 are too big.
Gimme a mo'....
 

John Baddeley

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Try these: only very slightly fuzzier than the first scans. I may try again, and put them in pdfs...
SCN_0002 lr.jpg
SCN_0003 lr.jpg


my pencilled marks down the left side
HTH
Thanks, John
 

PeterBJ

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Scanning nozzle checks can be tricky and might take some tweaking of scanner settings. I guess your coloured stripes actually are present and OK. But your nozzle check clearly shows that the pigment black is defective. The missing lines in the text document also indicates defective pigment black.

Here is a scan nozzle check from an MP620 that is OK and that uses the same print head. To keep the file size down, crop the scanned image to include only the essential. Also try turning off all auto image enhancements. This is scanned using the CCD scanner in an MP800 @ 100 dpi:

MP620 nozzle check 3.jpg
 

John Baddeley

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nozzle check23-08 a.png

This is over-contrasty compared with teh original pdf scan, but is accurate for the purpose here.

Here at last is the A4 of text at a sensible file size:
text lr.jpg
 

The Hat

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As suspected the PGBK is defective and won’t be coming back, but if you need to use the printer till you can acquire a new head, then set your Media to use matte photo paper and carry on using the plain paper and the printer will print just like normal, except your text won’t be water proof and it will print a bit slower, sorry we don’t have better news for you...
 
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