Hi Daniel,

Thanks for the info & suggestions.

I don't think it is a heating problem. I used fan control software for quite a 
while when the original HD failed and I was running from my backup clone on an 
external drive. However when I replaced the HD and installed the SSD I used the 
OWC provided temperature sensor/lead and now the inbuilt system temperature 
control seems to work well. The HD fan seems to run a little faster than the 
original setup (maybe the 3TB Toshiba generates a bit more heat than the 
original 1TB drive) but iStat menus shows all temperatures as normal and fans 
ramping up as required.

Previously, on hot days, the internal temperatures did rise enough to get the 
fans speeding up a bit (as expected) but never gave any problems. The problems 
have just been apparent this week when temperatures have not been high and fan 
speeds have been normal.

The hard drives were my first thought - which is why I booted from an external 
drive and ran the full disk utility repair process on all internal drives an 
volumes - which showed no problems. Since AHT IS showing a RAM problem I think 
I need to address the RAM first. If I get rid of the currently indicated RAM 
problem and find that I still have ongoing problems then I may need to look at 
installing the combo update or look at more extensive HD testing - but I prefer 
to address one thing at a time to give me a better feel for the problem.

I tried downloading remember but OSX won't let me open it because it is from an 
unidentified developer. I tried clicking the "open anyway" button but it still 
won't open - gives the same message. I guess I could change my security 
settings to allow apps downloaded from anywhere - but I'm reluctant to do that. 

I did read the Remember documentation though and note that it says:
--------------------------------------------------------------
Try the Apple Hardware Test CD or DVD first!
Macintosh computers currently ship with a version of the Apple Hardware Test 
(AHT), which can perform some fairly heavy duty memory tests on a computer. 
This should be one of the first lines of defense in diagnosing computer 
problems. Although the AHT test are thorough, they have not proven to find all 
defective memory. If these tests do not find the problem, then give Rember a 
try.

AND:
If have experience replacing hardware, the only way to locate defective memory 
chips is by deduction - guess and check or split-half method troubleshooting. 
This may be updated in the future. You may also attempt to run the Apple 
Hardware Test CD or DVD that comes with most Macs. This may give more 
information (if it finds the problem).
--------------------------------------------------------------

So it would seem that Remember won't actually indicate which module is faulty - 
and since AHT is already indicating a problem the maybe I just need to try the 
suggested deduction ;o)

The computer has been running OK since yesterday - but doing next to nothing as 
I work on the laptop - so I will run AHT again to be sure it still sees the 
problem - and then probably try the split-half method trouble shooting.

I will keep you informed on progress.


Cheers


Neil

----------------------------------------------------------------
On 13/03/19, 21:28, "Daniel Kerr" 
<[email protected] on behalf of 
[email protected]> wrote:

    Hi Neil
    
    Just a quick reply as finishing off some other work.
    
    A few things I would run to test it.
    (sometimes I find Apple RAM test not all that helpful, whereas the 
following is very good).
    Just be aware it can take a really really long time to test it all, as it 
does a huge amount of tests to all the modules. (I’ve seen some take hours to 
complete - 
    Rember - http://www.kelleycomputing.net/rember/
    
    I’d also run the hard drives just to rule them out. For a good program I 
use Smart Disk Utility from here - 
    (the demo is fine for a one off test).
    https://www.volitans-software.com/apps/smart-utility/
    
    Could also be something “heating up” perhaps? So it runs for a while, until 
a part is heated up a bit more. (unlikely, but worth a check anyway).
    For older iMac’s that have had hard drives replaced this is a good program 
to help control the Fans a bit more then the Apple one - 
    http://www.hddfancontrol.com
    
    But I’d be checking the RAM first would be my start.
    
    Hope something there helps. If I think of more, I’ll post back as well.
    Kind regards
    Daniel
    
    ---
    Daniel Kerr
    MacWizardry
    
    Phone: 0414 795 960
    Email: <daniel AT macwizardry.com.au>
    Web:   <http://www.macwizardry.com.au>
    
    
    **For everything Apple**
    
    NOTE: Any information provided in this email may be my personal opinion and 
as such should be taken accordingly, and may not be the views of MacWizardry. 
Any information provided does not offer or warrant any form of warranty or 
accept liability. It would be appreciated that if any information in this email 
is to be disseminated, distributed or copied, that permission by the author be 
requested. 
    
    > On 13 Mar 2019, at 8:52 pm, Neil Houghton <[email protected]> wrote:
    > 
    > Hi Ronni,
    >  
    > The problem is that all RAM modules show as OK both in System report and 
Etrecheck (which says the performance is Excellent) and it seems that the iMac 
thinks I have a fully functioning 24GB.
    >  
    > It is obviously something that only shows up in the more heavy duty 
checks that AHT uses.
    >  
    > The problem is that the error message does not seem to indicate which 
module is problematic - so I guess it is trial and error and repeated use of 
AHT?
    >  
    > Thanks
    >  
    >  
    > Neil
    >  
    > From: <[email protected]> on behalf of Ronni 
Brown <[email protected]>
    > Reply-To: <[email protected]>
    > Date: Wednesday, 13 March 2019 at 17:52
    > To: <[email protected]>
    > Subject: Re: Strange iMac freezes
    >  
    > Hi Neil,
    >  
    > Yes that AHT does indicate Bad Ram. On your menu bar go to: Apple > About 
This Mac > click on System Report... > then click on Memory in the Hardware 
section.
    > 
    > 
    > There you should be able to see which 0xb740bf98  module has failed and 
which slot it is installed in.
    > 
    > Kind Regards,
    > Ronni
    >  
    >  Ronni Brown’s iPad Pro 12.9-inch 256GB 
    >  
    > 
    > On 13 Mar 2019, at 5:18 pm, Neil Houghton <[email protected]> wrote:
    > 
    >> OK - prior to running the combo update I thought I’d run a couple more 
tests:
    >>  
    >> 1)  I ran the Apple Hardware Test (AHT) in extended mode and it did 
report a problem (on pass 1):
    >> 4MEM/9/4000000 0xb740bf98
    >> which I understand indicates a RAM problem.
    >>  
    >> 2)  I then ran Etrecheck which reported no problem except
    >> Last shutdown cause - 128- unknown
    >> However the time of this shutdown would match me hitting the shutdown 
button in Apple Hardware test - so not really a problem.
    >>  
    >> So, my current thinking is:
    >>  • AHT is finding a RAM problem
    >>  • The RAM passes the normal bootup RAM check
    >>  • Etrecheck shows all RAM modules check out OK
    >>  • The problem could be a (few) bad sector(s) on one RAM module
    >>  • Everything works fine until something tries to access the bad RAM 
sector(s)
    >>  
    >> I guess I now need to isolate the bad RAM module. Given I have 24GB RAM 
in 4 modules then, assuming there is just one problem module, the iMac should 
continue to work fine on either 20GB or 16GB (depending on the size of the 
faulty RAM) while I get the bad RAM replaced.
    >>  
    >> I may or may not need to run the combo update - depending on whether the 
various hard shutdowns have caused any corruptions problems.
    >>  
    >> I will keep you informed on progress.
    >>  
    >> Cheers
    >>  
    >>  
    >> Neil
    >>  
    >> From: <[email protected]> on behalf of Neil 
Houghton <[email protected]>
    >> Reply-To: "[email protected]" <[email protected]>
    >> Date: Tuesday, 12 March 2019 at 17:20
    >> To: "[email protected]" <[email protected]>
    >> Subject: Re: Strange iMac freezes
    >>  
    >> OK - further update - another freeze:
    >>  
    >> This time only MS Outlook was running and I was previewing attachments 
to an email (using the Outlook preview all button when the spinning beachball 
appeared.
    >> At first I could see both Outlook and Finder using the command-tab 
switcher and checking the fast user switching drop-down menu worked OK - 
showing my user account logged in.
    >>  
    >> Then more strangeness happened:
    >>  • All my desktop items “disappeared” though the desktop picture was 
still visible (if this had happened at the last freeze when using Firefox I 
would not have noticed since the desktop was obscured by the 2 Firefox windows)
    >>  • Command-tab now only showed Outlook and NOT Finder - as if Finder had 
somehow quit and not relaunched.
    >>  • I normally have the dock hidden but the cursor revealed it normally - 
showing no dot under the finder to show it was running.
    >>  • I clicked the finder icon in the dock (hoping to relaunch finder) and 
the desktop picture immediately disappeared leaving a black background.
    >>  
    >> Currently:
    >>  • Desktop is black but menubar and Outlook window are still showing.
    >>  • Mousing over the hidden dock no longer reveals it.
    >>  • The cursor shows the spinning beachball over the outlook window and 
menu items
    >>  • The Outlook window can be moved but not resized
    >>  • The cursor currently show the normal pointer over the right-hand 
Apple menu icons and the 1Password menu icon
    >>  • The cursor shows the spinning beachball over the Onedrive and Dropbox 
menu icons
    >>  • When the cursor is moused over the Malwarebytes menu icon it says 
“Background service is offline”
    >>  • When the cursor is moved over the black desktop, it does not change 
state - ie it stays as ether the normal pointer or as the beachball depending 
what the state was just prior to moving onto the “black”
    >>  
    >> Continuing:
    >>  • With the cursor over the Spotlight icon, it changed to the beachball 
and then the icon disappeared.
    >>  • Picking on an Apple menu icon to click - this time the wireless 
status icon - resulted in the cursor now showing the spinning ball over all the 
Apple menu icons
    >>  • Clicking on the 1Password and Malwarebytes menu icons also resulted 
in the cursor changing to showing the spinning ball over these menu icons
    >>  • This time the other Apple menu icons did not actually disappear from 
the menu bar.
    >>  
    >> The problem has now occurred both with Outlook only running and with 
Firefox only running and It now seems to me that the problem is not with either 
app but with some basic OSX functionality at the finder/dock level (or the 
processes running these functions).
    >>  
    >> I think Ronni’s suggestion for the combo update is my best bet at this 
point.
    >>  
    >> I will report back with my progress - or lack thereof  ;o)
    >>  
    >>  
    >> Cheers
    >>  
    >>  
    >> Neil
    >>  
    >>  
    >>  
    >>  
    >> From: <[email protected]> on behalf of Neil 
Houghton <[email protected]>
    >> Reply-To: "[email protected]" <[email protected]>
    >> Date: Tuesday, 12 March 2019 at 16:02
    >> To: "[email protected]" <[email protected]>
    >> Subject: Strange iMac freezes
    >>  
    >> Writing this from the laptop as my iMac has started playing up with 
strange ‘freezes’ the likes of which I’ve never seen before – and I’ve had my 
share of crashes, freezes & hangs over the years!!
    >>  
    >> First my setup/hardware – which has been “enhanced” since purchase:
    >>  • 27” iMac 2.8GHz i7 - late 2009 - running OSX 10.11.6
    >>  • 24GB RAM - 2x8GB + 2x4GB
    >>  • Internal Drive 1 - Mercury Electra 250GB SSD - boot drive containing 
OSX, applications and a bare “admin” user account
    >>  • Internal Drive 2 - 3TB Toshiba partitioned as:
    >> ·         1.5TB volume - containing main user folder plus other data 
folders
    >> ·         1.0TB volume - currently empty (earmarked for media files)
    >> ·         500GB volume - containing my previous SL boot volume
    >>  
    >> This has all been working fine since the rebuild to replace the HDs and 
boost the RAM.
    >>  
    >> I have been out of town for a couple of weeks but shut down the compute 
and UPS and removed the plugs from the wall - so no chance of “power glitches” 
while we were away.
    >>  
    >> On return everything fired up OK (from memory) but pretty soon I had a 
freeze - I don’t remember the exact sequence but, pretty soon I ended up with 
just a black screen with a cursor. The cursor continued to respond to the mouse 
but I could not “wake up” anything else. Command option escape would not open a 
force quit window and I had no means of knowing if any apps were still running. 
All I could do was power down using the power button on the back of the iMac.
    >>  
    >> All  booted up OK but fairly soon I ran into problems - again I don’t 
remember the exact sequence but I do remember the desktop going black whilst 
some open window remained visible but soon I was back at the black screen & 
cursor. Again, all I could do was power down using the power button on the back 
of the iMac. At this point, I was worried that I might have some drive problem 
so I rebooted from my backup clone and used disk utility to run first aid on 
all drives/partitions. I ran top level on both internal drives and then volume 
level on all four volumes - in all cases the repair went fine with no issues 
noted.
    >>  
    >> Back to booting normally and again all seemed fine - for awhile - until 
another freeze - I just remember I was using Outlook this time.
    >>  
    >> Sometime (I don’t remember when) during all this I remember Acrobat 
reader opening - unprompted - a couple of times. The first time barely 
registered - I just quit it - the second time made me think “why did it do 
that?” I was also trying to research OSX black screen problems - I found plenty 
of references to this problem but generally associated with incomplete system 
updates and none with similar circumstances to mine. One common thread on a 
numbers of these threads seemed to be down to some login problem which made me 
go the user preference pane where I noticed two new Adobe items in the login 
items list - which, I guess could explain the unexpected opening of Adobe 
reader. I have now removed the Adobe items from the login items list but my 
freeze problems persist and so this was probably non-related.
    >>  
    >>  
    >> The latest freeze is now ongoing – around 1 hour and I know that only a 
switch-off at the power button will get me out of it.
    >>  • In this case the only app open was Firefox with two multi-tab windows 
on screen and one multi-tab window minimised in the dock. It froze with the 
spinning beach ball cursor – which still tracks the mouse movements.
    >>  • Command-tab would not cycle me back to Finder.
    >>  • Option-Command-Escape would not bring up the force-quit menu.
    >>  • Mousing the cursor over the menu bar showed the spinning ball over 
all the Firefox menu items but the normal pointer over the right-hand Apple & 
3rd party menu items.
    >>  • I have the “fast user switching” menu item on so I clicked my user 
name to open the drop-down switching menu (I wanted to check if this looked 
“normal”) however, at that point most of the Apple menu items disappeared from 
the menu-bar. The Spotlight icon was still showing but clicking that turned the 
pointer to the beachball and, after a moment, the Spotlight icon also 
disappeared.
    >>  • At present, both Firefox windows are still showing and I can switch 
between windows by clicking each window – but not between tabs within the 
window.
    >>  • The menu bar still shows the left-hand Apple icon but the beachball 
cursor when over it. The full Firefox menu also shows – but again with the 
beachball.
    >>  • The Dropbox, 1Password, Malwarebytes and Onedrive menu icons are 
still showing – but now with the beachball (although originally the shoed the 
normal pointer cursor).
    >>  • Screen sleep initiated normally and the screen awoke from sleep 
normally with a keyboard input.
    >> UPDATE:  I have just shut down using the power button and rebooted and 
quit the only reopened app (Firefox) and, for the moment, all looks fine. For 
the moment, I will leave it running while I have lunch and see if runs into any 
problems just sitting quietly doing nothing (from a user perspective!)
    >>  
    >> UPDATE:  Well, it has been running fine for a couple of hours now (but 
doing nothing) including screen sleep and rewake and system sleep and 
rewake/login - so I guess I will go back to using it and see if I can find any 
sort off pattern to the problem.
    >>  
    >> Any thoughts/ideas/suggestions gratefully received.
    >>  
    >>  
    >> Cheers
    >>  
    >>  
    >> Neil
    >>  
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