Apple A1407 Display Does Not Always Display At Startup Unless Via F12?

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Apple Thunderbolt Display

27" display with 2560 x 1440 pixels resolution Thunderbolt & MagSafe cable attachments

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Phil Cam @philcam82437

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Publié: 24 juin 2020

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Apple A1407 Display Does Not Always Display At Startup Unless Via F12?

#1- Apple A1407 Display Does Not Always Display At Startup Unless Via F12 Voiceover commands for Username/Pword. Othertimes, perfect startup in a blink of the eye.

Thunderbolt Display connected to Mac mini 2018 MacOs 10.15.6 via Thunderbolt adapter to USB-C.

I’m skeptical of the display because no issues to TV but that’s HDMI signal not Thunderbolt. I’ve repaired the A1267 and hoping not to mess with this one.

#2-How hot is too hot for this display? Fan is running.

#3-Should Display USB ports always have constant power when Mac is off? Will not charge phone constanlty

Thanks in advance..

What’s supposed to be connected here?

No extra parts found

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Do you have access to another system which has a Thunderbolt or Thunderbolt2 connection Vs using the adapter to fit it to a Thunderbolt3 system? I wonder if your adapter is good.

24 juin 2020 par Dan

Good question. It's a new adapter. Apples Store didn't have the 2meter thunder bolt cable to bypass the AIO cable so I snagged the adapter anyway. Thinking the same thing. No change in behavior.

24 juin 2020 par Phil Cam

Thanks for the lead, Dan! I tested it myself. There was some board swelling down from the caps. Ever since I got this off CL with a shrink wrapped cable (person used the shrink wrap to reinforce the vulnerable cable end) I started hoarding new Apple parts like a new AIO cable, and vesa mount (for small TV wall mount). I knew eventually this Display will need parts just like the 24" I refurbed. Found a new fan and PSU in box so I grabbed them both. Cleaned what I could wipe, while replacing PSU, fan, and AIO cable. Fan thermistor (?) must be fine since the fan runs and continuity tested ok. Display starts fast, runs cool, too. iFixed it.

1 juil. 2020 par Phil Cam

Review Step 15 here Remplacement du câble Thunderbolt et MagSafe

2 juil. 2020 par Dan

Ordered LCD Thermal Sensor 922-9943. Sensor is located near the leads below the PSU.

3 juil. 2020 par Phil Cam

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Dan @danj

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Publié: 24 juin 2020

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What I find interesting is the Fn 12 is the volume up key, so why would this alter the display? Thats just so odd!

The display does have a speaker! So the signal is being passed via TB to the audio processor within the display to increase the volume. But why would that make a difference? Apple Thunderbolt Display Teardown Review Step 11

You also talked about loosing power on the USB ports. The ports are powered by the displays power supply and should stay on with or without your system running.

So thats point to the power supply as suspect! I would open the unit and check the voltages to see if I could narrow down if the power supply or the logic board needs attention.

The fan unit has a thermal sensor within it. If you look at the fan you’ll see you have the fan power and tach connection and the second is the thermal sensor

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Thanks, Dan! Can you please point us to the tech manual for this and will continuity tests suffice for this? I’m not comfortable yet testing with the glass and screen off while it’s plugged in. Maybe that just it’s supposed to be done.

24 juin 2020 par Phil Cam

Knowing your limits is good! Time to find someone with the deeper skills. For reference you should be able to located the schematics for your display. Search for the board number 820-2997.

24 juin 2020 par Dan

Replaced PSU, AIO, and fan with sealed new. USB only charges when mini is off. Mini does not recognize display speakers, either. I doubled checked internal connections again today. No where can I find what 2-Pin wire lead goes to the 2-pin connector below the upper left ground of the Logic board. There were only two leads to the fan. No extra parts. Rest Pram, SMC, disconnected cords, etc. I had a tech guide for the 24" need one for the 27", please.

1 juil. 2020 par Phil Cam

On step 8 picture 1 of the teardown guide there is a 2-pin connector on the Logic Board next to the 3-pin fan sensor connector. What is this for? No extra leads anywhere to find to plug into this. A local authorized shop couldnt answer it and sent two pics of logic boards not using this connector. Weird..

2 juil. 2020 par Phil Cam

@Phil Cam - See my update above

2 juil. 2020 par Dan

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Do you have access to another system which has a Thunderbolt or Thunderbolt2 connection Vs using the adapter to fit it to a Thunderbolt3 system? I wonder if your adapter is good. — Dan
Good question. It's a new adapter. Apples Store didn't have the 2meter thunder bolt cable to bypass the AIO cable so I snagged the adapter anyway. Thinking the same thing. No change in behavior. — Phil Cam
Thanks for the lead, Dan! I tested it myself. There was some board swelling down from the caps. Ever since I got this off CL with a shrink wrapped cable (person used the shrink wrap to reinforce the vulnerable cable end) I started hoarding new Apple parts like a new AIO cable, and vesa mount (for small TV wall mount). I knew eventually this Display will need parts just like the 24" I refurbed. Found a new fan and PSU in box so I grabbed them both. Cleaned what I could wipe, while replacing PSU, fan, and AIO cable. Fan thermistor (?) must be fine since the fan runs and continuity tested ok. Display starts fast, runs cool, too. iFixed it. — Phil Cam
Review Step 15 here Remplacement du câble Thunderbolt et MagSafe — Dan
Ordered LCD Thermal Sensor 922-9943. Sensor is located near the leads below the PSU. — Phil Cam
Thanks, Dan! Can you please point us to the tech manual for this and will continuity tests suffice for this? I’m not comfortable yet testing with the glass and screen off while it’s plugged in. Maybe that just it’s supposed to be done. — Phil Cam
Knowing your limits is good! Time to find someone with the deeper skills. For reference you should be able to located the schematics for your display. Search for the board number 820-2997. — Dan
Replaced PSU, AIO, and fan with sealed new. USB only charges when mini is off. Mini does not recognize display speakers, either. I doubled checked internal connections again today. No where can I find what 2-Pin wire lead goes to the 2-pin connector below the upper left ground of the Logic board. There were only two leads to the fan. No extra parts. Rest Pram, SMC, disconnected cords, etc. I had a tech guide for the 24" need one for the 27", please. — Phil Cam
On step 8 picture 1 of the teardown guide there is a 2-pin connector on the Logic Board next to the 3-pin fan sensor connector. What is this for? No extra leads anywhere to find to plug into this. A local authorized shop couldnt answer it and sent two pics of logic boards not using this connector. Weird.. — Phil Cam

Phil Cam @philcam82437 Rep: 21 1 2 · Answer 1 · 2020-07-04T13:44:20-07:00

Phil Cam @philcam82437

Rep: 21

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Publié: 4 juil. 2020

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Replacement AIO cable listed as NEW, has a defective Thunderbolt Cable.

Connecting the A1407 Display directly to the 2018 Mac Mini with a dedicated ThunderBolt cable (plus adapter) yielded a perfectly operating display with Display Brightness control, speakers, mic, camera, etc.

Seller is sending another AIO and the elusive missing LCD Thermal Sensor that was stumping the pros. Logic Board ok at this time.

Case closed. Thanks!

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Apple Thunderbolt Display

Apple A1407 Display Does Not Always Display At Startup Unless Via F12?

Update (07/02/2020)

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Update (07/02/2020)

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