apple magic keyboard a1314 schematic - Page 1
Forum section: electronics / repair

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 02, 2025, 07:32:21 am
content: Hi,I have a magic keyboard A1314 that does not turn on. I get the standby voltage of ~3V, but pressing the power button does not turn it on.Measuring the main components, they seem fine, but I still cannot find the short. No liquid remains or oxidation components were found.So, is there a PCB schematic of the logic board available?Regards,

author: thm_w
author_rank: Super Contributor
timestamp: June 02, 2025, 11:51:58 pm
content: Why do you think there is a short if the voltage on the batteries is 3V?If you disconnect the batteries what is the resistance across that voltage input? What is the resistance across the power rails?https://discussions.apple.com/thread/253861214?sortBy=rankhttps://www.ifixit.com/Device/Apple_Wireless_KeyboardThis should be in the repair section of the forum:https://www.eevblog.com/forum/repair/

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 03, 2025, 01:09:31 pm
content: Quote from: thm_w on June 02, 2025, 11:51:58 pmThe voltage near the power button (located to the other side of the PCB) is indeed ~3V. But pushing the power button does not power up the device. Between the Broadcom Bluetooth IC and this push button there are other ICs like voltage regulators, transistors etc. The shortage is somewhere in this part.It's almost impossible to measure the resistance of all power rails. It's a two layer PCB with many through holes that connect these layers. As far as I tested now they all seem ok.Anyway this is not a repair question but rather a schematic request, that why I post it to this topic.

author: Simmed
author_rank: Frequent Contributor
timestamp: June 03, 2025, 01:22:31 pm
content: since you already opened it up and made measurementswhy dont you post some pics of the PCBmaybe someone may know where else you should measure to find the problem

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 03, 2025, 05:55:13 pm
content: Quote from: Simmed on June 03, 2025, 01:22:31 pmSome pics of the PCB as requested

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 03, 2025, 06:09:21 pm
content: Another set of pictures

author: thm_w
author_rank: Super Contributor
timestamp: June 03, 2025, 10:59:57 pm
content: Quote from: sdancer75 on June 03, 2025, 01:09:31 pmMeasure across the large ceramic capacitors, if there is a short it is likely to be there.Every power rail will have a large ceramic across it.

author: fzabkar
author_rank: Super Contributor
timestamp: June 04, 2025, 02:47:05 am
content: I can see these test points:PP2V0_RPP1V5_VDD_CORE

author: Simmed
author_rank: Frequent Contributor
timestamp: June 04, 2025, 04:23:43 am
content: nicelooks like there is 1v5 and 2v0 railso there maybe a powergood sense chip ?that commands the 2 bucks to startup and power up 1v5 2v0i see a L7 and L9, that maybe the area of the 2 buckshmmmm nope doesnt look like bucks ?in pic xxx6809_copyi am guessing the right side wires go to battery ?but what does the left side spring do?ifixit no schemahttps://www.ifixit.com/Guide/Disassembling+the+Board+Power+Button+and+Battery+Compartment+of+an+Apple+Wireless+Keyboard/13438but it appears in ifixit comment, the switch was a problem after some trauma

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 04, 2025, 05:17:10 am
content: Quote from: Simmed on June 04, 2025, 04:23:43 amIt is surely not the switch or the LED diode (i.e, burned LED or shorted). I tested them thoroughly. They work perfectly.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 04, 2025, 05:21:27 am
content: Quote from: fzabkar on June 04, 2025, 02:47:05 amI don't remember well right now, but I can say that PP2V0_R gets the battery voltage ~2.8V. Nothing else.I will recheck it as soon as I return home.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 04, 2025, 05:23:48 am
content: Quote from: thm_w on June 03, 2025, 10:59:57 pmI measure the ground from both sides. They also seem ok. Only one side is grounded.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 06, 2025, 11:27:26 am
content: Ok, I found it, the C28 capacitor is shorted.Of course, this may be a false alarm (there is no noticeable discoloration appearing on the capacitor itself) since the IC itself, which may be connected to this, is shorted.I will desolder it and measure it outside the circuit.

author: BradC
author_rank: Super Contributor
timestamp: June 06, 2025, 11:35:04 am
content: Quote from: sdancer75 on June 06, 2025, 11:27:26 amI've had 2 shorted MLCCs in one of my Apple Thunderbolt displays (3 years apart) on the 5V rail. The Bob Parker ESR meter was useful in helping track those down.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 06, 2025, 11:39:32 am
content: Quote from: BradC on June 06, 2025, 11:35:04 amI need to remove it to perform any tests effectively. Is ESR a factor we should test when discussing ceramic capacitors? I do this only for electrolytic counterparts.

author: BradC
author_rank: Super Contributor
timestamp: June 06, 2025, 11:41:53 am
content: Quote from: sdancer75 on June 06, 2025, 11:39:32 amDon't worry about ESR. Don't even bother testing the cap, just remove it and see if the short on the rail disappears. If not then you either put the cap back or replace it with a new one. In my case the cap was shorted so I had to take a guess at its value. I just used what I had on the bench.MLCCs can be "problematic" when hand soldering, so be prepared for issues down the track. I've been lucky so far but I know one day I'll probably walk in to a dead monitor again and have to re-do the process.

author: wraper
author_rank: Unknown
timestamp: June 06, 2025, 12:09:10 pm
content: Quote from: sdancer75 on June 03, 2025, 01:09:31 pmIt's a nonsensical conclusion. Most of the failures are not short circuit.

author: thm_w
author_rank: Super Contributor
timestamp: June 06, 2025, 09:33:12 pm
content: Ignoring water damage, I'd guess most macbook failures are shorted MLCCs? But from the link above keyboard failures seemed to be other issues mostly.MLCC usually would be discolored or cracked, but, that is in high current devices. So if its low current device and it shorts out you might not see anything.Anyway let us know if the cap fixes it. Some ICs with low core voltage will have low resistance <10ohm (GPUs and CPUs), but in this case I don't think it should be that low?

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 11, 2025, 06:01:20 pm
content: Bad news, that's what I was afraid of.Ceramic capacitor is found ok. The short is at the Broadcom bluetooth IC.