IPhone 6S No Image: Difference between revisions

IPhone 6S No Image
Device	IPhone 6S
Affects part(s)	Motherboard
Needs equipment	Soldering Iron, Hot-Air Station, Microscope
Difficulty	◉◉◉◌ Hard
Type	Soldering

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Latest revision as of 23:42, 2 December 2025

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Problem description

The Device turns on but it has no image.

Symptoms

Device boots but no image is displayed

Solution

The no image problem can have 2 causes a bad display or a motherboard problem.

Diagnostic Steps

The first thing to do is to always rule out bad parts, so first try a new display on the phone if it works great all that is need is a screen replacement.

If even with a new display the phone is unable to display any image the problem is on the motherboard.

Start by inspecting the FPC connector for any liquid or physical damage.

If everything is fine take diode readings of the display FPC and compare them with the image bellow.

If the diode readings you took are ok next thing to check is if the voltages need to display image are present.

PP5V7_LCM_AVDDH_CONN
PN5V7_LCM_MESON_AVDDN_CONN
PP1V8_LCM_CONN
PP5V7_MESON_AVDDH_CONN

These voltages can be measured here and only show up with the device turned on.

It is common to have a short circuit on one of these lines, most of these lines also have a filter that acts kinda like a fuse and may open if there is overcurrent.

If the voltages are present, the issue is likely on the MIPI lines. Most of these lines go straight to the CPU through a filter. If every filter is present and testing good, the fault is most likely within the CPU itself.

Here is a Block diagram of how the picture circuit works.

Repair Steps

If by replacing by trying a new display the image fault is solved all you have to do its to replace the display.

If there is a any physical damage to the FPC the solution is to replace it. The best method is to use a hot air station to desolder the old FPC, clean the old solder from the motherboard, apply new solder, align the new FPC, and use the hot air station to solder it. Be careful not to use excessive heat, as you may cause a solder bridge under the motherboard.

When taking diode readings of the FPC, if you measure a line that should read, for example, 0.500V but get 0.100V or 0.000V, it indicates a short on that line. The best way to trace the short is to inject voltage into the line with a DCPS and use a thermal camera to identify which component heats up. Fallow this guide how to find the short Short Circuits - Repair Basics

If you measure a line that should read 0.500V but get OL (Open Line), it indicates a disconnection in the circuit. To trace the issue, consult the board view to follow the line’s path.

If you have to replace a Filter the best way is to use your hot air station with a low air speed or the component may fly away.

If any of the voltages are missing, use the block diagram to trace where the voltage is generated and replace the chip responsible for creating that voltage. These components are easily available online and are generally easy to find.

Final Testing

After assembling the phone, ensure every function is working as expected, not just the display, there are a lot of small components around the LCD FPC and when heating this area sometimes you end up desoldering something by mistake.

@@ Line 1: / Line 1: @@
-'''820-3662 NO NUMERIC KEYS / CAPS LOCK INVERTED / INPUT DELAY - TOUCHPAD ISSUES'''
+{{Repair Guide
+|Device=IPhone 6S
+|Affects parts=Motherboard
+|Needs equipment=Soldering Iron, Hot-Air Station, Microscope
+|Type=Soldering
+|Difficulty=3. Hard
+}}
+{{stub}}
+== Problem description ==
+<!--
+Provide a concise description of the issue here. Be  as specific as possible to help readers quickly determine whether or not this is the exact problem they are facing.
+ -->
-The device arrived with the numeric keys on the internal keyboard non‐functional, despite a complete keyboard replacement. Visible moisture and sulfation were detected near the keyboard’s SPI controller (U4801).
+The Device turns on but it has no image.
+== Symptoms ==
+<!--
+Detail all measurable or observable symptoms in this section.
+-->
+* Device boots but no image is displayed
-🔍 '''Step-by-Step Diagnosis'''
+== Solution ==
+<!--
+If the issue has a single, specific solution, provide it in this section and delete the sub-headers below. Otherwise, if there are multiple potential causes for the problem, outline the process of identifying the root cause and offer corresponding solutions below.
-Visual inspection: Corrosion was found near the keyboard/trackpad controller area (U4801).
+-->
-Voltage drop across R4814 (relevant resistor in the SPI circuit) was checked and confirmed expected values.
+The no image problem can have 2 causes a bad display or a motherboard problem.
-'''''Chip replacement attempts:
+=== Diagnostic Steps ===
-'''
+The first thing to do is to always rule out bad parts, so first try a new display on the phone if it works great all that is need is a screen replacement.
-'''First attempt:'''
+If even with a new display the phone is unable to display any image the problem is on the motherboard.
-Replaced U4801 with a donor chip from board 820-3476 (MacBook A1502).
+Start by inspecting the FPC connector for any liquid or physical damage.
+[[File:Iphone 6s lcd fpc.jpg|center|thumb|iPhone 6S LCD FPC]]
+If everything is fine take diode readings of the display FPC and compare them with the image bellow.
+[[File:PlaceHolder image.png|center|thumb]]
-🟡 Result: Keyboard worked, but Caps Lock LED was reversed (lit when lowercase, off when uppercase).
-'''Second attempt:'''
+If the diode readings you took are ok next thing to check is if the voltages need to display image are present.
+* PP5V7_LCM_AVDDH_CONN
+* PN5V7_LCM_MESON_AVDDN_CONN
+* PP1V8_LCM_CONN
+* PP5V7_MESON_AVDDH_CONN
-Used a chip from MacBook A1278 (Unibody).
+These voltages can be measured here and only show up with the device turned on.
+[[File:IPhone 6S Display Voltages.jpg|center|thumb]]
+It is common to have a short circuit on one of these lines, most of these lines also have a filter that acts kinda like a fuse and may open if there is overcurrent.
-🔴 Result: Severe input delay, no trackpad and overall poor keyboard behavior.
+If the voltages are present, the issue is likely on the MIPI lines. Most of these lines go straight to the CPU through a filter. If every filter is present and testing good, the fault is most likely within the CPU itself.
-'''Final solution:'''
+Here is a Block diagram of how the picture circuit works.
-Replaced with U5701 from donor board 820-3332.
+[[File:IPhone 6S Display Block Diagram.png|center|thumb|600x600px]]
-✅ Result: Keyboard fully functional, Caps Lock LED working properly, no delay, trackpad also fully operational.
+== Repair Steps ==
+If by replacing by trying a new display the image fault is solved all you have to do its to replace the display.
-'''⚙️ Technical Conclusion'''
+If there is a any physical damage to the FPC the solution is to replace it. The best method is to use a hot air station to desolder the old FPC, clean the old solder from the motherboard, apply new solder, align the new FPC, and use the hot air station to solder it. Be careful not to use excessive heat, as you may cause a solder bridge under the motherboard.
-The U4801/U5701 keyboard SPI controller contains firmware/configuration specific to each board model. These chips are not freely interchangeable between different MacBook series (A1278, A1502, A1398, etc.).
+When taking diode readings of the FPC, if you measure a line that should read, for example, 0.500V but get 0.100V or 0.000V, it indicates a short on that line. The best way to trace the short is to inject voltage into the line with a DCPS and use a thermal camera to identify which component heats up. Fallow this guide how to find the short [[Short Circuits - Repair Basics]]
-⚠️ '''Using an incompatible IC can cause:'''
+If you measure a line that should read 0.500V but get OL (Open Line), it indicates a disconnection in the circuit. To trace the issue, consult the board view to follow the line’s path.
-Reversed Caps Lock LED logic.
+If you have to replace a Filter the best way is to use your hot air station with a low air speed or the component may fly away.
-Noticeable input delay on keys input.
+If any of the voltages are missing, use the block diagram to trace where the voltage is generated and replace the chip responsible for creating that voltage. These components are easily available online and are generally easy to find.
-Malfunctions with the trackpad or power button.
+== Final Testing ==
+After assembling the phone, ensure every function is working as expected, not just the display, there are a lot of small components around the LCD FPC and when heating this area sometimes you end up desoldering something by mistake.
-✅ '''Key Takeaway'''
-“The keyboard IC (U4801/U5701) must come from a firmware-compatible logic board. Although they are electrically identical, their internal configuration depends on the board model and its interaction with the SMC.”
-— Diógenes el Perro
-🛠️ Note: Neither the BIOS nor the SMC were reprogrammed during this repair.