I’ve been in and out under and over this issue, by myself and with a fleet of HP engineers.
It is not a belt or bad fan bushings or anything we think of as associated with a squeal.
It is “capacitance squeal” almost impossible to track down because of the intermittence. HP once rebuilt the entire electronics of one of my printers and it still did not solve the issue. Ultimately, they made the wise decision to walk away from it.
The printer would sound a very high pitched squeal or screech, then, continue operating as normal. The screech did not affect the operation of the printer.
It’s a “ghost in the machine” kind of thing. It involves interaction between the capacitance and current fluctuations between IC board components, similar to the electronic equivalent of harmonic vibration in vehicles where due to the amount of wear or mis-alignment, the front end goes into a wobble at certain speeds yet works out of it above or below that point where it shakes everything.
Best thing to do is when it starts to happen: quickly avert your ears, or cover them with your hands and talk loudly saying: “I’m not listening”, and repeat this loudly until the squeal stops.... :-)
Seriously (all kidding aside), to my knowledge there is nothing that can be done about this. Try to find it and you will open a can of worms. But if you are H-bent on finding and fixing it, just open your wallet and throw the money on the ground - it will be a lot easier.
It will get worse over time, but I doubt that it will be much worse.
If the printer has trouble restarting or begins to get hung, unplug it and let it dissipate for several hours, or best, overnight, then plug back in and it should get back up and go.
-Mark
