iMac won't sleep whilst my USB printer is attached

Question

iMac won't sleep whilst my USB printer is attached

Hi everyone,

I'm running the latest High Sierra on a 27" 2011 iMac.

It has recently stopped going to sleep when left unattended or when I Opt-Cmd-Eject the screen. The iMac will run a screensaver, but it will never switch off the display, instead the screen goes black for a couple of seconds and then bounces back to the desktop. I've worked through Apple's help pages at:

If your Mac doesn't sleep or wake when expected - Apple Support

And the problem persists, but by unplugging everything and then reconnecting them one by one, I have narrowed the cause down to bmy USB Samsung ML-2160 laser printer. The iMac sleeps as normal if the printer is either unplugged or removed from Printer System.

The problem affects all users on the machine (I set up a new, empty test account and that doesn't sleep either).

So far I have:

Removed and reinstalled the printer in System Preferences.
Reset the printer system from within System Preferences.
Updated the printer drivers.
Moved the printer from connecting through the iMac's own USB to each of two different hubs and then to a Time Capsule's USB port.
Unchecked all sharing preferences and disabled wake on network access/wake on demand.
Disabled Bluetooth.
Returned all energy saving preferences to their default values.
Reset the SMC and NVRAM.
Reinstalled High Sierra (although not yet wiped the disk and started again).

Anyone got any other ideas what I could try to get to the bottom of this?

Many thanks,

Mike.

iMac, macOS High Sierra (10.13.2), 16GB RAM

Posted on Dec 14, 2017 4:52 AM

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Answer 1

Best reply

John Galt

Level 10

141,162 points

Dec 14, 2017 5:15 AM in response to Mike Richards2

Mike, you did everything I would have done, with the possible exception of examining your system for a "printer status monitor" or something like it that it may have installed. That's assuming you actually downloaded and installed a printer-specific driver (which usually isn't necessary). Those things are typically used to monitor the printer's status such as toner or ink levels, and serve as little more than an annoyance.

If its installer included something like that, it is likely to be in one of the following folders:

/Library/LaunchAgents

or possibly

/Library/LaunchDaemons

There should be very few files in either one of them. Post their contents if you are uncertain.

If they don't contain anything pertaining to the printer, then you're not likely to be able to fix the problem on your own, and should contact HP for support (which is certain to be an unpleasant experience).

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Answer 2

Dec 14, 2017 5:17 AM in response to John Galt

Hi John,

That's very useful - thanks. I've looked in both folders and can't see anything from either Samsung or - oh dear god - HP, but the printer does have a live view of supply levels, so there must be something running somewhere.

I guess a request to HP support might be necessary - life is so cruel!

Mike.

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Answer 3

John Galt

Level 10

141,162 points

Dec 14, 2017 5:39 AM in response to Mike Richards2

They are almost certain to blame Apple, and Apple is just as certain to blame them. I don't want to discourage you but it's almost not worth the effort.

The fact sleep is inhibited when connected to your TC's USB port is most curious to me. Obviously some communication is going on with it, preventing sleep. If you're motivated to do so, you can use the following short script to potentially identify the process or processes preventing sleep:

clear; printf '\e[3J'; pmset -g log | sed -E '/UUID|Assert/d' | tail -n 40

It may or may not reveal anything interesting.

Since Apple is more likely to take an interest in you as a customer and be proactive in addressing the problem, I'd start with them: Contact Support. Unlike HP it's guaranteed to be a pleasant experience, even if they can't help. They may take an interest in collecting data which they might forward to their engineers for examination, and perhaps inform HP of a problem (who still won't care).

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