should I replace my Canon MX850?

[Tin Ho]

If you read the intervening posts, you will see that what looked like clogged yellow nozzles was apparently in fact caused by dried ink deposited on the bottom of the print head and after pvrbulls cleaned the bottom of the print head, those random nozzle patterns disappeared.

How do you propose that continuing to use a printer with clogged nozzles can lead to an electrical problem?

Removing the print head from the printer to soak and clean it is what leads to an electrical problem. That's why I have urged people to try to get the printer to clean its own print head and only soak it as a last resort.

Clogged print head has little or no ink flow. The print head nozzles get burned out which then leads to the symptom of electronic defect when you continue to use the printer. One of your advices given to people probably includes one that tells people not to use the printer if there is a clog. I may be mistaken. You may have given other advices but this one.

There is no foundation in physics, chemistry or electronics that by taking the print head out to soak and clean would lead to an electrical problem. If you search the internet you will see hundreds, if not thousands, of posts from people who soaked printeads. I have done it many times, sometimes over night or even over many days with no ill effect. It is often the only way to unclog a print head. Your advise does not make a good logic here.

I read the whole thread. You have no way of knowing if pvrbulls has done any printing after cleaning the bottom of the print head. If he has done some printing, even just one sheet, it could kill the print head. Print head clogging almost never get unclogged by a simple cleaning of the print head surface. If you ever experienced a real clogging you should have known that.

 

[ghwellsjr]

My understanding is that if there is no ink flow to cool the heating element for each nozzle, then that one heating element can burn out, but I wouldn't call that an electrical problem because it is impossible to know if it really is a burned out heating element or still just a clogged nozzle. There's always hope that individual random nozzles that don't work can eventually be unclogged and start working again, that is, unless you continue to use the printer and eventually burn out the heating element. That is why we warn people not to use their printer, except for nozzle checks when there are clogged nozzles.

But once a heating element has burned out, there is no further risk to the rest of the print head by printing. I have several print heads with one or two nozzles that don't print and I use them with no further degradation.

Are you aware that there is a lot of microelectronics inside a print head? Here is a picture I took of the bottom of a print head where you can see some of these electronics showing through the clear epoxy:

If you don't think you can permanently burn out the electronics by powering up a device that is wet, then why don't you call your cell phone provider and tell them you dropped your cell phone in the water and you want them to replace it for free. Let us know what they say.

I agree that if you wait long enough for the electronics to dry (a day or two) then there is little risk to cleaning the print head outside the printer, but many people, myself included, are sometimes impatient and can't wait to see if the cleaning worked. I have not only burned out a print head, I have also burned out a printer by not following my own advice with regard to making sure a print head was completely dry before turning on the printer.

I don't know what pvrbulls did before he posted his nozzle checks on post #10 but they looked like yellow ink was migrating from the bottom quarter of the yellow nozzles up to the region just above that and looking like more nozzles were sort of working but the fact that the yellow was showing up to the right of the bars just to the left of the nozzle patterns indicated to me that this was not the case and so I asked him to clean the bottom of his print head which he did and produced the nozzle check on post #13 which was completely clean about the bottom 1/4 of the nozzle area. This convinced me that the apparent nozzle pattern above the bottom 1/4 was simply an artifact and not real. I was not thinking that he had clogged nozzles and that cleaning the bottom of the print head would unclog them. Do you understand what I am saying? So whenever the top 3/4 of the yellow nozzles got burned out, it wasn't because of the cleaning during his posts. It happened before he started posting.

 

[Tin Ho]

Wow, a picture like that does have a bit more convincing power than the truth. I understand why many people argued with you now. You have discredit all I said, and proabably all by those who had heated debate with you. You just discredited hundreds of people who have done it and there were not hundreds of dead print heads from doing that. There si nothing else I can say. Nothing will change your mind. Let's end this thread gracefully.

Oh, by the way, I do know electronics. I have been working with chips for over 30 years. Not just playing with them. I do everything from simulation to tape out to bring-up and all that. I bread boarded a system with microprocessor and chips before CAD tools were available. I built instruments for testing the mechanical structure of a F-16 in an air force base in Florida. Thank you for telling me not to throw my cell phone into water. This has to be the best advice I received today.

 

[bsanotrun]

I agree that if you wait long enough for the electronics to dry (a day or two) then there is little risk to cleaning the print head outside the printer, but many people, myself included, are sometimes impatient and can't wait to see if the cleaning worked. I have not only burned out a print head, I have also burned out a printer by not following my own advice with regard to making sure a print head was completely dry before turning on the printer.
.

But You don't need to completely immerse the printhead in cleaning fluid, and if you have taken out a canon print head that has had a lot of use the underneath is usually covered in ink so it has, by design, to be relatively immune to wetness.
The i865 i was recently given had sat without ink carts for almost 3years so needed extreme cleaning.
I found plastic pipe with an internal dia of 4.5mm for the colour and 8mm for the 3e-black fitted over the inlet ports, which i filled with cleaning fluid
The tray the head sat on [1] was made so only the very bottom of the printhead was kept wet as the fluid eventually started to flow through the nozzles, the excess drained out onto tissue paper, it took three weeks but it now works perfectly
[1] very crude but effective jam jar lid with two cutouts made so the head sat at the correct hight.

 

[ghwellsjr]

Yes, bsanotrun, like I said in post #12, if you're just getting cleaning solution on the bottom of the print head, you don't have to wait a long time for it to dry and in fact I advised doing it quickly. But my admonition to wait a couple days for it to dry was for those people who soak their print head by submerging or placing under running tap water.

 

[Tin Ho]

Conductivity of Copper is roughly about 10 millions times of that of drinking water. It is about 1 million times of that of sea water. The tap water may be not very clean. It still should have a conductivity of about 1/5 millionth of Copper or less. The voltage existing in the print head should be only low DC/AC voltage. The conductivity of the water in a wet print head may cause leakage current of some micro amps. It will not cause anything to burn. What can cause a print head to be electrically damaged is static. When static builds up it may reach a voltage high enough to suddenly discharge and destroy electronic components especially MOS/CMOS devices in the print head. Static will not build up if the print head is wet.

Dirty water can cause problems to electronic PCBs or chips. There may be tiny silver wirings under high density chips. Trapped moisture under high density chips with tiny silver wirings may cause silver atoms to migrate and cause circuits shorted. The PCB dies if this happens. This will not happen right after soaking a PCB in water. It usually happens 6 to 12 months after that. This was a bug found about 20 to 25 years ago in some old generation computers. The silver migration bug no longer exists today.

There is a risk always when a print head is removed and reinstalled. Canon's design is vague that you never know if the print head is correctly positioned before you pull down the clamp. There is a good chance to destroy a print head if the print head id positioned in a particular wrong place at a wrong time. Most likely the printer will complain that it can not recognize it. In a worse case the print head may be badly shorted and damaged.

There is another risk involving soaking a print head. WHen a print head is soaked it is facing down. If the bottom of the container that the print head sits on to soak is rough it may scratch the print head surface by accident. This is a possibility. I don't really know how likely this can happen. It should be a common sense that if the print head surface is scratched by hard object it can be damaged.

Soaking a print head gives it a better chance to recover. The risk is you may lose it. It's up to you to decide if you want to do it.