"I saw you have a 2012 Mac mini and a Yamaha receiver setup mentioned in an article from a couple years ago (general tips for OS X surround sound) and want to ask for any ideas about the problem we're seeing with a RX-A2040 replacement receiver. Our Onkyo failed again and we got a great deal on an 'open box' 2040 that appears unused, which we really like in general but it's been basically useless with the Mac Mini. The TV's display blacks out for a second or two about every 7 seconds, like clockwork. No problems if directly connecting the mini HDMI to the TV, so the HDMI cable must be OK. (Assuming the AVR to TV video is ok for other things (disc playback, etc), otherwise I'd suggest trying that cable with the mini to TV connection just to ensure it's not a factor. Also assume total HDMI cable run is not extremely long.)
    Along with finding your article, I also saw some owners in apple's support forum with the exact same problem using (2014 series) RX-A1040/2040/3040 receivers - Mac Mini HMDI Chronic HDTV Refresh Problem?, but no resolution yet as of last post on Dec 21st. And one user said the problem does not happen in bootcamp/Windows on his mini, just in OS X. Like others with this problem, I've tried the usual resetting SMC and NVRAM. (HDMI cable to AVR worked ok with Mini direct connected to TV.)
    I know your Yamaha is an older Aventage model (an RX-A2000, 2010 era) but hoping you have some suggestions to try before we return the 2040.
Thanks in advance.
-Erik"

Seems like a handshake problem. I don't have the constantly repeating blackouts on my 2012 Mac Mini/AVR setup, but I do see an initial black screen for a second or two (twice in a row) at initial boot up or wake from sleep. Annoying but after that, video is stable. (1080P 2012 Samsung ES, Yamaha RX-A2000, also later tested with RX-A3050 Receiver and LG 55EF9500 OLED UHD TV OK, using 2012 Mac Mini with OS X 10.9.5 and EFI/bootrom updated, although I never had the HDMI problems many 2012 mini owners had early on. Long thread/article on that from late 2012/early 2013. EFI update released to address that but it didn't help everyone.)
   Not sure what model/resolution your TV is (or your OS version, mini bootrom current?) but here are some things to check/try off the top of my head. Although posts/comments are often from Mac Mini owners, I've seen a couple similar reports from iMac owners but I suspect the mini is one of the most popular macs to be used with AVRs as part of a media center setup. Granted some Mac mini models have had more than their share of video related problems reported IMO.

Some General Tips for Mac Display/HDMI Problems:
• Power On Sequence (Display first, Source last):
  Power on the TV/Display (wait 5 seconds), then the A/V Receiver (and switch to the HDMI input the Mac uses). Then turn the Mac on. (If the Mac boots without a display connected/detected, graphics drivers may not load which can cause performance problems.)
  
  Tips for the Mac and OS X:
  
• Is Mac's firmware and software up to date? (for the OS X version used)
  (Some OS X 10.11.x users have reported general display problems, A 2014 mini owner also noted he had no HDMI/receiver problems (video flicker/dropout) until updating to El Capitan, although he also mentioned using screen sharing. (Disable it - see below. Also check for incompatible 3rd party addons.) If you're using El Capitan, do you have any other drives with an older OS X version to test?)
• Do you have screen sharing enabled? (or any screen recording, Mirroring, USB video addon, etc.) If so try disabling it. These were Tips for OS X HDCP Errors here from the past. (Since one affected owner reported no problems in bootcamp (Windows), I'm curious if an OS X setting/add-on is a factor. And best to simplify the setup as much as possible when troubleshooting, including disconnecting anything not required from the Mac.)
• Is Mac's Display Prefs set to correct resolution? (setting supported by TV/Display)
  (Assume so as you said it worked with a direct connect, just not though the AVR. Resetting NVRAM clears stored resolution, but not a cure for everything. Also try a safe mode boot.) One user said going to System Preferences > Displays and changing "Scaling" to the setting above 'default' (and restarting) helped.
• Can you play iTunes store HD Video (HDCP required) with direct to TV HDMI connection?
• Typically Cables are the first suspect (especially if using higher than 1080P or 1920x1200 modes or long cable runs), although some users noted the same cable chain was OK in Bootcamp, but not OS X. (Sometimes even a cable disconnect/reconnect and power cycle of the Mac and display helps.) Keep total cable run lengths as short as possible, and avoid using HDMI switches/splitters, separate right angle adapters, etc. - direct HDMI to HDMI connections (with good cables) help minimize the chance of problems. Now that 18Gbps Certified Premium HDMI cables are under $10 for 6ft lengths at some sources, it's worth a try as sooner or later you'll need a HDMI 2.0/18Gbps cable. I've tried a 6ft $9.96 "blackweb" brand cable (HDMI Premium Certified with QR Code/holographic fingerprint) from a Walmart local store and it was reliable at 4K/UHD 60P 12-bit 4:2:2 (appx 17.8Gbps rate) in 4K/UHD Player tests. (4:2:2 used as 4K/UHD 4:4:4 at 60Hz is only supported at 8-bit in HDMI 2.0, 4K 60Hz 4:4:4 at 10-bit/12-Bit exceeds the HDMI 2.0 spec max rate.)
• Does the same problem happen with a Mini DisplayPort to HDMI adapter? (Instead of using the Mac's HDMI port.)
• In case of a corrupted macOS file/prefs/driver, do you have another bootable drive?
• If all else fails, try an Active HDMI adapter. (In some cases these have helped.)
• If you can't get a reliable HDMI display at all (not just a problem in OS X), there's always a chance the Mac's HDMI port is damaged or has failed. (If possible, test with a known good, short cable direct to a 1080P (or lower res) display/TV.) Apple's Hardware Test may not find all failures.
  
  Tips for the Yamaha Receiver (check owners manual for settings info)
  
• Is the receiver set to not process video? (just pass it through)
• Is the receiver set to a fixed output resolution matching the TV? (vs 'Auto' detect)
• If your receiver has dual HDMI outputs, are both connections to HDCP displays?
  (try using only the main HDMI output to rule out any issues with HDMI out 2)
• Is HDMI control/CEC enabled?
  (if so disable it as a test, although if using ARC, that requires enabling it on TV and AVR)
• 4K Mode Setting in Advanced Setup:
  On 4K capable Yamaha receivers, "Advanced Setup" has two 4K output modes. The default is Mode 2 (4K at 4:2:0 only). Mode 1 supports 4k @60Hz/50Hz 4:4:4, 4:2:2 or 4:2:0 - but the Front Aux HDMI Input only supports 4K at 4:2:0 per manual. Note that 4K 50/60Hz 4:4:4 is only supported at 8-Bit per HDMI 2.0 Spec (4:4:4 @4K 60P/50P is too high a data rate) - 10-bit/12-bit 4K 60Hz/50Hz supported at 4:2:2 or 4:2:0 only. (I mention the front Aux input 4K 4:2:0 limit as some users with video dropouts using rear inputs said only the front Aux input was stable. But didn't mention what Mode was set in Advanced Setup.) See user manual for details on Advanced Setup (Note below), which can only be changed using the front panel buttons, not via remote control and only shown on the Receiver's display. 4K with Mode 2 setting (especially with 60Hz/4:4:4) may have problems with long cables or those not rated for high speeds. (Yamaha note says to use 18Gbps rated cable for Mode 1 high bandwidth.) If you have problems with one mode, try the other to see if it helps.
• Is the A/V Receivers's firmware up to date?
  (FYI: Yamaha has posted firmware updates for many of their Receivers. You can search for updates for your AVR model number at USA Yamaha support site updates page. I update using the firmware download on a USB Flash drive. My Audio/Home Theater page has a frequently updated List of Firmware Updates for TVs, AV Receivers, & 4K/UHD Players, most recent update first.)
• Does the AVR HDMI port(s) work with other devices/computers? (One owner with this problem noted it was only seen with OS X, not bootcamp/windows and one mini owner said his Macbook worked fine with the same AVR/HDMI port.) Do you have another computer (mac or PC) to test it with to confirm AVR HDMI is ok? (some models of AVRs are infamous for HDMI board failures.)
• I don't like hot-plugging cables although some have done that, I avoid it. Worth a try to reinsert the cable (ensure seated) with power off. Or try another HDMI input in case of a suspect or damaged connector. (Sometimes this forces a re-detect of the display.)

Note: Some settings on these Yamaha receivers (including 4K output mode options) are only available via the "Advanced" setup, accessed from the front panel buttons (under the drop down cover). With receiver off, hold down the "Straight" button and then press power on. Info/settings appear on the receiver's display only - not the TV. Then scroll through the setup/configuration options using the "Program" rocker switch. Check your Yamaha user manual's Advanced Setup topic for the exact steps.

The above may not help, but just things that come to mind to try. My A2000 is set for no video processing and HDMI control is Off for both AVR and TV. I know someone that recently upgraded to a 3050 (2015 model w/HDMI 2.0 and HDCP 2.2 on all rear ports) but not sure he has access to mac mini to test. I'll ask but that's a different AVR model. (See update below for tests with RX-A3050 model.) I remember he's mentioned it seemed slow to switch inputs (TV displays no connection for a second, then syncs OK) and also mentioned it seemed slow to sync audio after changes (like fast forwarding, reverse, changing disc audio format, etc.), but loves it otherwise.

If all else fails you could connect the Mini's HDMI to the TV and Optical audio out to the receiver. Another option would be trying ARC from the TV to the Receiver, with the Mini's HDMI connected to TV. That may result in just stereo from the Mini as it likely sees the TV has having only stereo speakers, although I've never tried it. (I have used ARC for TV channel audio to the receiver, but not for audio from a TV connected Mac.)

Update - my 2012 Mini (running OS X 10.9.5) works OK with Yamaha RX-A3050:
I don't know anyone locally with a Yamaha RX-A2040/3040 model, but took my 2012 Mini (OS X 10.9.5, no 3rd party addons, no sharing enabled) to a friend that has a (2015) Yamaha RX-A3050 to see if that newer model had the repeated blackout (every 7 seconds) problem that some 2040/3040 owners reported in the Apple forums. (No problems with Mini connected to my 2010 RX-A2000 receiver, except for the above mentioned initial two-step handshake on boot or wake from sleep.) The 2015 x050 models have HDMI 2.0a/HDCP 2.2 support (for 4K DRM, although '.a' HDR support not in 1.63 firmware, but should be in v1.77 and later), the x040 models have HDMI 2.0 but not HDCP 2.2. (They support HDCP of course, but not v2.2 required for 4K/UHD DRM.)
   He uses a 4K/UHD TV (LG 55EF9500) and the Yamaha AVR has an advanced setup option (accessed via front panel buttons - see 3050/2050 PDF manual page 158) with 4K Output Options for Mode 1 (4K 60Hz/50Hz input/output at 4:4:4, 4:2:2 or 4:2:0. Front panel Aux HDMI is still 4:2:0) and Mode 2 (4K at 4:2:0). Mode 2 is the default and used for the A3050/Mac Mini tests.

   I connected the mini (with my old/no brand name 6ft HDMI cable I'd used for at least 5 years) to the rear HDMI AV4 input (he's using HDMI 1/2/3 for 2 Blu-ray players and a Sony CX-7000 blu-ray 400 disc changer). Did the usual power on sequence (noted above - TV first, AVR 2nd, then Mac) and it worked fine. (Showed the same initial 2-step blackout at initial power up as I mentioned on my RX-A2000 except it was faster, TV used was a 2015 UHD LG 55EF9500 OLED.) And after waking from sleep it only did a single blackout vs twice with my A2000. After that, no issues seen in about an hour of use including updates/reboots, OTA HD TV SNL recorded video playback. TV set to "Just Scan" mode, and upscaled 1080P (1920x1080) from the mini to the LG's native UHD (3840 x 2160) looked great. (And that OLED black level was stunning - apple firmware update screen had perfect black with no clouding. If not for near-black issues with some content, it'd be perfect. (Don't care about Dolby Vision/UHD HDR Premium certification.) Passive 3D on the LG UHD OLED was the best I've ever seen - full HD per eye (actually 3840 x 1080 vs 1920 x 540 with Passive 3D on 1080P displays), no ghosting/crosstalk (viewed at appx screen center vertically) and bright. Included passive 3d glasses were very light weight and comfortable. (He also had clip-ons for use with corrective lenses.) The wire walk scene from 'The Walk' 3D blu-ray on it was amazing.)

The RX-A3050 had firmware 1.63 update (current as of this Jan 4th, 2016 post date), with HDMI control off, BT off and using only 1 of the 2 HDMI outputs. Since I hadn't updated the Mac Mini to the latest EFI Security Update 2015-002 (it had 2015-001 installed), I applied that update while connected to the RX-A3050/LG OLED. It installed/rebooted fine (and applied another OS X update afterwards that also required a reboot - no issues). With my 2012 mini HDMI through the 3050, only 1 handshake/blackout after reboot (or wake from sleep), vs 2 in a row with my old A2000.

After I returned I saw a post from 'Wolf1' that suggested using another HDMI input that was not HDCP marked but none are on my A2000 or the A3050. (Later realized he may have assumed the AV1 input "BD/DVD" marking meant others didn't support HDCP, but they all do. It's marked that way because the default Scene 1 button is set for movies and mapped to that input.) Although the front HDMI port on the 3050 does not support HDCP 2.2 required for 4K DRM (manual page 45 note, not sure about earlier HDCP version), . (Verified in Yamaha's user manual.) And of course they support older HDCP to work with blu-ray players for instance. Crutchfield's product page for the 3050 (and 2050) also notes "HDCP 2.2 support on all rear-panel HDMI connections".

All rear HDMI inputs support HDCP even on my 2010 (first Aventage series) A2000 model but of course not the newest v2.2 for 4K DRM. (Usually OS X HDCP problems are seen when trying to play DRM'd (protected) content, but see my notes below from the 2040/3040 manual.) His later post said switching inputs (not sure if front or rear) solved his problem of repeated blackouts on his A3050 model. Since I had no issues with my 2012 Mini using the rear HDMI inputs on the same 3050 model receiver (or an older A2000 model), I wonder if any of the above notes on settings apply to his OS X/AVR setup. (The PDF Yamaha 3050/2050 user manual confirms All 7 rear HDMI Inputs work for Blu-Ray players, therefore they do support HDCP and my 2012 mini worked on the rear HDMI inputs.

If the mini didn't support HDCP at all, even Apple's iTunes store HD content would not play when directly connected to HDCP supported displays, although HDCP errors in OS X are not uncommon. (Which is why I posted the OS X HDCP tips long before these AVR problem posts. They've happened with direct connections to TVs/Displays.) It's not a mac mini hardware issue - if it was, I'd have seen the problem also. My Late 2012 Mac mini has OS X 10.9.5/all updates to date now, but no screen sharing, mirroring or 3rd party OS add-ons used. (For those with HDCP problems, again check the tips/notes above.)
   The AV1 HDMI input is marked "BD/DVD", since it's the default input for the "Scene 1" button (which has Movie settings), but all rear ports support HDCP. (HDCP is a necessary evil for playback of any DRM'd HD material, including iTunes HD video, even netflix I think. HDCP must be supported by all devices in the entire chain from source to display.)

I didn't test using the 3050's front HDMI (non-HDCP 2.2), since the rear inputs worked and would normally be preferred for this. (The front HDMI port behind the drop-down cover is typically used for temporary connections with portable devices. I've used my A2000's front port with a Camcorder, and I think once with an iPad w/HDMI adapter IIRC. (I used a MDP to HDMI adapter once with a 2009 MacBook Pro but can't remember if I used the AVR or directly connected it to the TV.) Personally I wouldn't want to leave the front cover down and a cable connected there long-term.)

Update 2: A reply in the Apple thread on Jan. 8, 2016 from a Mini 5,2 (mid-2011, running El Capitan) owner with Yamaha 3040 (upgraded from RX-V1067 that worked OK) said the mini connected to the 3040's front HDMI port was stable, but not happy having a cable connected on the front. I also wonder if the front HDMI input has video processed like the rear inputs do if the AVR option is set for that. (Also see notes below from 2040/3040 user manual, front port listed as HDMI/MHL which glossary notes is HDCP compatible.) He's the user that said (bootcamp) Windows on the mini worked fine with the 2040 receiver using the rear HDMI ports, but not in OS X. I'm curious if any of the above Tips & Notes apply to his system/setup. (And if using a non-HDCP input helps, that still means you can't play any DRM'd/protected content from the Mac, so I'd at least check the HDCP tips I listed above.) Since he mentioned running El Capitan, I saw a post in a different thread that 10.11.3 beta fixed display problems (waking displays from sleep) some had reported with 10.11.2.

Update 3: Later posts think there's an issue using a 2011 (AMD graphics) Mini with the 3040/2040's rear HDMI inputs. At least using OS X - as a 2011 mini owner said no problems using Bootcamp/Windows 10 with the rear HDMI inputs, but had the repeated (every 7 seconds) blackout problem with OS X (El Capitan) on the same Mac mini. (He also noted applying 2040 firmware v1.77 (beta?) from Yamaha support, which didn't help.) This is why I'm curious about affected owner's OS X details/settings. One post said Yamaha had confirmed it also (interesting as usually most AVR mfrs don't have macs to test or don't make the effort). A 3040 Yamaha owner said his 2011 mini has the issue with rear inputs, but worked on the front Aux HDMI input, although his 2014 mini worked with the rear HDMI inputs. (2012 and later Mac Minis use Intel integrated graphics.) FYI: See notes above on Yamaha 4K receiver's front Aux HDMI input 4K 4:2:0 limit, regardless of the 4K Mode setting in Advanced Setup.

Also saw a Jan 10, 2016 dated post from an (unspecified model/OS) iMac owner:

"I had the EXACT same issue you guys were all having on my iMac - blinking HDMI on my TV every 7 seconds. I looked in the Yamaha manual - HDMI ports 1-3 have HDCP, the rest don't. I tried hooking the HDMI for the iMac into one of the ports without HDCP. Boom, the problem was gone."

But again no details (Yamaha model, manual page number, OS/settings details). I've never seen a Yamaha receiver that just had HDCP on HDMI AV1-AV3 inputs only so I downloaded the (USA) Yamaha RX-A2040/3040 PDF user manual from Crutchfield.com (top link on RX-A2040 "details" page) and searched for that note on HDMI inputs and could not find any note that only AV1-3 support HDCP - page 38 shows all 7 rear HDMI inputs usable for Blu-Ray players, which of course require HDCP for blu-ray disc playback. (The entire HDMI chain must support HDCP for playback.) I also could not find any note that said the front HDMI/MHL port didn't support HDCP either (in fact the opposite - see below).

I wish he'd posted a manual page number in case the search/index missed it. In fact, I didn't see where the 2040/3040 manual said the front HDMI input (which a mini owner used OK), labeled HDMI/MHL in manual front cover drawing, didn't support HDCP - in fact the Glossary page 163 says "As with HDMI, MHL complies with HDCP (High-Bandwidth Digital Content Protection)". The same page also has a HDMI note on HDCP support with no mention of any HDMI input that doesn't support HDCP. (None of the x040 series support HDCP 2.2 for 4K DRM content playback, however that's not the subject here.) Searching the 2040/3040 manual for "HDCP" only finds troubleshooting (p155/157, about TVs that don't support it), p163 (glossary) and 170/173 (glossary) pages. (Page 170 bottom notes (blue "!") says "the unit is not compatible with HDCP-incompatible HDMI or DVI devices", but the mini's used (2011/2012) in problem reports do support HDCP (otherwise even Apple's HD iTunes store content would not play, although as mentioned above there has been OS/software related HDCP problems in some setups, not always resolved. (And some OS versions/software/drivers or firmware (any device) could have bugs affecting this. Even swapping ports could force the mini to re-detect/refresh the display info. There's a ton of variables possible and typically very few details mentioned in problem reports.) That's why I listed the tips/notes above.)

And from that 'incompatible' with non-HDCP HDMI (or DVI) devices note in the manual, why would any HDMI input not be HDCP compatible, or work with the Mac on any HDMI input if that was the core problem. (There can be causes for HDCP problems with Macs/OS X (see past notes here) but it has worked on some HDMI inputs even for those with problems originally - and on the same HDMI input using bootcamp/windows on a mini that had the problem in OS X only. And again I could not replicate the problem with my mini using the rear HDMI inputs on the same 3050 receiver model used by one mac owner with problems, but our OS X version (and perhaps enabled OS options) were different. But I don't have access to a 2040/3040 model, only the A2000 and 3050 models - both worked without having to use a front HDMI input. Changing inputs worked for some (blaming HDCP, but manual I checked didn't confirm that), but I'd like to know more - including their OS X settings (if no screen sharing, recording, mirroring used) and AVR settings (list above) and if they can play iTunes store HD video that requires HDCP when using a direct to TV HDMI connection. (I don't own any iTunes store HD content personally and they may not either.) I don't post at apple's forums, but if I did I'd mention all the info here, as it has a lot more detail/notes than what is posted to date there.

And BTW, also saw another thread in Apple's forums on HDMI problems some Mac mini owner's reported with other brands of A/V receivers - a 2011 Mini with Marantz 1605, unspecified mini with Marantz 1604 and a 2011 mini with Denon x4100. (One 2011 Mac Mini/Denon AVR owner later said he had no problems with a MacBook connected to the same HDMI input that the Mini had problems with.) Like the other thread, those posts also didn't include any details on the above OS X/AV Receiver settings questions however. (And a later post in the first linked thread from a 2012 mini owner (OS X 10.9.5) that just started using an HDMI receiver (Denon X3100W) saying he's also seeing this problem. Direct connects to his projector were OK.)

Another reply from a reader on cables and (EDID) workarounds:

"I would first swap the HDMI cables just because it is so easy and cheap.
(Agreed, cables are a first suspect. He mentioned using same cable for direct to TV OK, but there's another cable from the AVR to the TV, although the same cables worked with bootcamp/Win on the same Mini for one affected owner. Only OS X had the problem.)
I have had HDMI cables work with displays but when a AV receiver is introduced you have problems as described. If that doesn't work, a common solution is a EDID emulator such as this one.
ConnectPRO TMDS-KITU1, HDMI EDID/DDC Video Ghosting Emulator ($64 @AMZ when posted on Jan. 4, 2016 but link later showed no longer available).
Often the EDID info can be stripped or misdetected when a AV controller is introduced in between the two devices.
Hope this helps,
Mike F. "

Thanks for link. That's one reason why I mentioned verifying the AVR was set for no video processing, just pass through. But EDID tweaks were used to address some mini owner's problems in the past even for direct connections. The (long) page from 2012 on the original problems with 2012 Mini video (which I didn't see personally) included some EDID notes/tweaks and a link to a (more expensive) Gefen HDMI Detective Plus. That ConnectPRO model is almost $40 cheaper. I've never used either of these but does it support HDCP? (Didn't see that listed at Amazon's summary but not checked mfr specs. Text search on page for HDCP found nothing but one user review mentioned a blu-ray player in his setup so maybe it does.)

"In late November our workhorse 2009 Mac Pro started to become unreliable, crashes or lockups became so frequent it was unusable. With no nearby Apple store we took it to a local computer repair shop that was recommended by a friend for diagnosis. Two days later they called saying it needed a new CPU board and said that sort of repair should be done by Apple as they did not have access to the part and proper procedures to swap the CPUs (hopefully OK) into the new board. So I paid the $95 diagnostics fee and decided to hold off on any repairs until my son returned from college for Christmas and have him look at it. A week later while at best buy we bought a new iMac (on sale), almost an impulse buy really but it was christmas and we hadn't bought a new mac since 2009.
   When our son came home for Christmas the first thing he did was pull the CPU tray out and within a few minutes said he'd spotted a problem - a retainer for a heat sink had broken off, the one under the CPU heat sink. He had seen an article on your site about this. (Reference our post with photos on 2009-2012 Mac Pro Northbridge High Temperatures due to broken Heatsink Retainer. Can cause shutdowns or kernel panics.)
    Long story short, after a trip to the hardware store, getting some thermal paste (repair shop) and a couple hours later it was up and running. *Knock on wood*, so far it seems reliable again. I doubt there will ever be another Mac that's as upgradeable, so I plan to hang on to it as long as possible.
(And you can easily replace drives and video card in a Mac Pro Tower. The later iMacs are glued shut, although it can be opened and resealed, most won't want to do that.)
   Although we like the new iMac a lot, not sure we would have bought it had the mac pro not been down. On the plus side we now have a second computer and are looking to explore thunderbolt. The new iMac is also surprisingly fast, although there's some things about the latest OS I don't care for but that's another story.
Just writing as my experience may remind other Mac Pro owners to check these.
Best Regards and Happy New Year, Robert."

• Apple Web Server notifications (security fixes)
  
  
• How to Check your storage on your iPhone, iPad, and iPod touch
  (Apple later removed iPod touch from the title.)

Topic-based page of How-To, Troubleshooting & Tips for Mac/OS X/iOS Users.