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모델 A1418 / Late 2013 / 2.7 & 2.9 GHz Core i5 또는 3.1 GHz Core i7 프로세서

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iMac A1418 late 2013 - white noise from headphone jack

Hi there,

I recently purchased a 2nd hand logicboard for my A1418 iMac from late 2013. Even though the board was claimed to be in fully working condition, there seems to be an unpleasant surprise with the headphone jack/ external audio port.

By plugging in (any) headphones there is only a white noise (which sometimes changes while adjusting the volume over the menu bar of the iMac). Anyway, the internal speakers as well as sound via bluetooth devices work flawlessly,

As I was assuming that it might be due to a faulty headphone jack, I tried to replace it by one from an A1418 Mid 2014 iMac (I think they must be interchangeable?!)- however with no success.

Does anyone have had a similar problem or have a hint were to look next? It is likely to be a hardware problem. I therefore also inspected the logicboard in the area close to the port for the headphone jack for any mechanical damage - at least there is no obvious damage present.

I would be very grateful for any advice ;-)

Thanks a lot!

Update (10/17/2019)

Hi all,

Some time ago I posted the above issue with the audio jack of my iMac. Well, as I couldn’t figure out the cause back then, I switched to a bluetooth headset. Anyway, now I got back to this problem…

I found out that DZ6503, which is close to the head phone jack connector on the board to be shorted to ground. As this component seems to be a ‘no stuff’ component, meaning that it does not exist physically, I tried to trace the short circuit back and ended up at C6256 which seemed to be shorted (both sides continuity to ground). After I desoldered it I was quiet surprised, that the short circuit still existed.

While the afore-mentioned capacitor connects to MAX97220_BIAS at U6250 my theory would be that U6250 seems to be faulty.

But, before I deep dive into swapping out this IC I just wanted to consult you, if my approach generally makes sense or if there might be another culprit.

Rgds

Update (07/25/2020)

Update:

I meanwhile was able to trace down the short on DZ6503 which happened to occur because of a short of Pins 10 (MAX97220 _OUTL) and Pin 11 (MAX97220_BIAS) on U6250. As I had a donor board laying around (well, not quiet a coincidence as it has been the one which was meant to be replaced by this, allegedly fully working board) I was able to confirm, that the short seem to be unusual)

To make things short, I replaced U6250 et voilà I do now have sound via the headphone jack!

Nevertheless I still encounter a disturbance noise on the right headphone speaker, which especially is noticeable while listening to more silent parts of videos and songs. So unfortunately something else seems to have gone bad (possibly also by trying to fix the previous issue).

Anyway, I definitely made some progress in this matter and maybe I am soon able to finally close this case for good! Just wanted to provide this intermediate step in case someone encounters similar issues.

@danj

Do you by any chance have advice on where to look for the culprit? I’d assume that there could be another short somewhere in the circuit from the right headphone speaker …

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@lycos - Sorry I have no magic here ;-{ The logic board clearly has a problem, why didn't you send the bad logic board back?

The problem is there are a lot of noise damping caps all it takes in one bad one.

@danj

thanks for the quick reply, I expected that this (still) might not be an easy task :/

Anyway, I might give it another try the next days.

Well, the thing with sending it back in the first place, was that I got it from Craigslist and of course the seller was not replying to my mails after - I cannot really say if he was aware of this fault or not - Anyway I now am happy, that I seem to be on the right track :)

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White noise issues tend to be issues within the audio circuit on the logic board. If you look at the iMac Intel 21.5" EMC 2638 Teardown Step 5 you’ll see the Analog Devices SSM3302 audio amplifier location I would look around if for damaged or missing SMT devices using your original board as reference.

Frankly, I think you need to send the logic board back.

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Hi @danj,

thanks for your input, I’ll definitely take a closer look at the mentioned spots! I also was suspecting the audio circuit, but as the sound from the internal speakers does not seem to be affected / both work fine, I’d might rather pay attention to the circuit of the audio jack. Or do you think the issue could still derive from components of the amplifier area?

…currently I am looking for schematics for this board to find out.

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