MG7550: error 6502 after soaking printhead

ninj

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Hi folks

Can anyone tell me what stupid thing I've done wrong?

Background: my MG7550 has been unused for a year or so, apart from light scanning duties, as it was in need of a printhead cleaning that I never got around to. So I finally soaked the printhead in Fairy liquid for a few hours (kept warm on the heated bed of my 3D-printer at 50-60C). I dried it thoroughly by leaving it in the airflow of a dehumidifier for a few hours. I handled it carefully to avoid damaging contacts, etc. However, after replacing it in the printer and starting up, the printer goes through the usual machinations and then stops with a 6502 error. Another clue: if I start it up without carts, it doesn't say there are no carts but instead says the the following carts were unrecognised (and shows pics of all of the colours). So whereas before I at least had use of the scanner, now I can't do anything with it (at no time did I attempt to print with blocked nozzles, by the way). Time for a new printer, or are there any tricks I can try?

Thanks.
 

PeterBJ

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I think the error is not related to the print head but instead to the chips or the chip contacts in the print head carriage. To determine presence of a cartridge the LED on the chip is detected by an ink sensor. There could also be a problem with that sensor.

The service manual for the MG7550 which is of the PGI-550/CKI-551 cartridge generation is nowhere to be found, but here is a service manual for the MG8120 which is of a previous ink cartridge generation. I think it is somewhat similar to the MG7550 so maybe the manual is useful? See page 11/70 for error 6502 and page 68/70 for the ink sensor which is pos. 9.

If you get the printer going and want to do some service mode operations then don't use version 3600 or older. The use of these service tools will block access to service mode. Instead use a version 4720 or newer. See this post for a free download of the version 4720 and notice the warning about a possible virus.
 

ninj

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Thank you @PeterBJ for that really helpful reply. I'm going to dive in and see what can do. Will report back.

Incidentally, FWIW ClamAV reports the 4720 service tool as virus-free. As I'm on Linux I'm not too worried and would run the service tool on a disposable virtual machine.
 

ninj

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Progress! I found an old set of OEM starter carts (nearly empty) and the printer is happy with them. It's strange that the compatible carts that were previously working very well in this printer are now producing the 6502 error (even a fresh set). Unfortunately I don't currently have any bulk ink to test out my refillables.

For what it's worth I did a nozzle check and got better results than I was expecting, though far from perfect. The PGBK channel is completely absent (could be the cart, though it wasn't reporting even near empty) and the M and GY are a bit blocked in the finer dot sizes.

I was rather looking forward to taking a screwdriver to my printer, but it seems like I no longer need to. At least I have access to the scanner again. Thanks again @PeterBJ .
 
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