The problem occurred twice and each time it sat with the cartridges in place. Clogs as stubborn as this do not occur that easily. Many folks approach the transistor in that they are either on or off. I have already described that those states are but two of three failure modes. With the third failure mode, you can get a leaky or partially on transistor or one that conducts erratically. If this is sufficient to put the nozzle in a partial on state, you will get the ink in the nozzle clogging over time due to dehydration, if the on state is at a high level, you get the ink solidified and a serious clog is a result. I've had enough experience building high performance hi fi amplifiers and should have seen this possibility years ago and should have realized something about this earlier.
Now when the transistor is at a leaky state, all bets are off on in its conduction characteristics...thus when used, it heats up a bit as normal but at these higher temps it may fail to work. The only argument is that at higher temps the gain should increase...but we don't know the circuits that are actually defective and when something doesn't work right...it is unpredictable to a certain degree.
OEM and flushed carts have been tried and not shown to be ink starved as very earlier it was described as such....but we should not dismiss the possibility of electronic failure.
My MG8120 printhead is such a victim. I still use it as it prints perfectly in high resolution mode, but somewhere the signalling and conduction in non high resolution mode is defective. I suspect my old Pro9000 was also a victim. It took out two printheads and the second one lasted less than 50 prints and the same channel was affected....ink? as fresh as it gets from different batches at each refill and I get my shipment at least once a month. That led me to suspect the printer logic board as the culprit. I know of another one where overnight the printhead on one channel becomes clogged and with the second printhead, something identical occurs...that one smells of logic board to high heaven. All printers had their power on continuously.
As a result, I would now favor only turning on the printer when it is needed..something that Canon recommends. Maybe they know or are aware of something?
