Request for A2115 iMAC 2020 5K schematics

[mon2]

Hi. Have a request for schematics / boardview files for this model. Will check the logic board # once at the office but unit has been toyed with another repair shop and has no power. No onboard LEDs so suspecting the 300W Delta power supply is defective after a power brown out event.

Have another confirmed good power supply in transit for testing later today / tomorrow.

Will appreciate any feedback and schematics, if available.

Thanks.

[mon2]

Re: Request for A2115 iMAC 2020 5K schematics

Update: Logic Board 820-01779-A

1) replacement 300W power supply arrived from Amazon - it is a generic 300W unit that is NOT Delta and is NOT LiteON but looks identical. Sold by ICTION from Shenzhen whom we have used for assorted products with success. The cost was very fair to buy it locally and was received the next day.

Bad news: The fault of this 2020 iMAC 5K is NOT the power supply.

The unit does not show any sign of life / no leds / no fan spin after a brown out event. Probing assorted caps and each is with 0 volts. 12VDC does indeed enter the logic board through the molex cable harness.

Will review with the original power supply after this setup shows some sign of life.

2) After watching this great video:

https://www.youtube.com/watch?v=GIHSyamWnh4

have the logic board out. Was not as elgant of a procedure as shown in the video but it is out.

3) Found that the ACE controller onboard is the CD3218 x 2 on this logic board. That is a new one to me. Next thorn in the ACE line of devices.

4) So far, unable to locate the schematics so will compare against the A1419 schematics which shows that there is a voltage regulator to create the PPBUS_G3H. Work for tomorrow.

[grmac5]

Re: Request for A2115 iMAC 2020 5K schematics

I have an iMac with exact same problem. Just died. I thought would be Power supply but opened and no LED on but yet PowerSupply is sending 12V. Checked mine with infrared while in the housing and nothing getting hot on screen side anyway. Wondering if this could be a T2 issue? Thinking of trying to restore DFU. Not sure if that makes sense.

[grmac5]

Re: Request for A2115 iMAC 2020 5K schematics

I ended up finding a shorted Cap on the backside of the board. One of the big coils at the bottom of the board (above the 3v3 coil) was shorted direct to ground. Pulled the coil and diode checked which side. Applied very low voltage and discovered nearby cap was getting hot. Replaced it and mine is running again.

[mon2]

Re: Request for A2115 iMAC 2020 5K schematics

Thanks for your feedback @grmac5. Have not had time to revisit the repair but will inspect before Friday. Will update the thread once there is a resolution.

[mon2]

Re: Request for A2115 iMAC 2020 5K schematics

Just got back to this repair. Found a shorted cap on the 5v rail. Replaced it and now can confirm that the rail is without the 0R4 (0.4 ohms) to ground short.

Applied a known good power supply -> 12v from the power supply is fine and reaches the logic board. No other power rail is showing in the testing.

Will appreciate if anyone has schematics or bv files for this model. Will continue to compare against the older models as this logic board appears to be similar.

The very first DEBUG LED is not ON which denotes that the AC is plugged in. This LED is powered from (using older schematics), the PP3V3_S5 rail so we can logically assume that this rail is not available. This rail (from older schematics) is based on the ISL6238 which also supplies the PP5V_S4_REG and this 5v rail is also missing. Will investigate to see if this common regulator is onboard and its status.

[smzlwan223]

Re: Request for A2115 iMAC 2020 5K schematics

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A2115,初步看了你的维修过程，这个机器的上电时序的先弄明白，要不然，修起来很吃力，虽然这款机器没有电路图点位图，但是可以很确定的是，大致的上电流程和以往的机器差不了多少，1，待机部分，也就是主板4个灯第一个灯，灯亮代表，主板待机正常，维修修这个部分，可以参考，A2159主板待机部分来修，因为，T2，与A2159类似。待机上电时序，大概是，1，公共端12v正常之后，给3.3v,待机IC供电，输出3.3v，再给T2主电源供电，T2电源再输出，相应的电压，如果是后继有短路，就会保护没有电压输出，你维修的时候，可以用可调电流表，来修复图，把电压调制为12V 电流最好是10A，当然前提测试12V公共端，是否有短路。希望能帮到你！
A2115, after a preliminary look at your maintenance process, you should first understand the power on timing of this machine. Otherwise, it will be very difficult to repair. Although this machine does not have a circuit diagram and a bitmap, it can be sure that the general power on process is not much different from that of previous machines. 1. The standby part, that is, the first light of the four lights on the mainboard, means that the mainboard is in normal standby. This part can be referred to for maintenance, The standby part of the a2159 mainboard is repaired because T2 is similar to a2159. Standby power on sequence, probably after 1, common terminal 12V is normal