Intel MacBook PM_SLP_S4_L Missing: Power-On Sequence and Diagnosis
Intel MacBook PM_SLP_S4_L Missing: Power-On Sequence and Diagnosis PM_SLP_S4_L is one of the most useful checkpoints on older Intel Mac logic boards. If PP3V3_S5 is present but PP5V_S3, PP3V3_S3 or the memory rail never appears, this signal helps identify where the power-on sequence stopped. However, a 0 V multimeter reading does not automatically prove that […]
Why Apple Service Centres Won’t Fix Your Logic Board
Have you ever visited an Apple authorised service centre just to be told your MacBook is unfixable? It happens quite frequently, and this is because the MacBook’s logic board is faulty. This page will explain why Apple authorised service centres cannot fix faulty logic boards and about Apple centre logic board repair. Mac Repairs Dependence […]
Spilled water on MacBook? Here’s what to do
IT-Tech Online Spilled water on MacBook? Here’s what to do Your MacBook has encountered a common mishap – water spillage, leading to unresponsive keyboard and trackpad, and even an automatic shutdown. What to do now? Spilled water on MacBook is a very common Mac disaster. Don’t worry. Follow this step-by-step guide to save your liquid […]
How does My Macbook Power up
How does my MacBook power on? 1. Once you connect MagSafe power adapter to the Mac, the System Management Controller (SMC) will talk to the chip on the MagSafe and the green light turns on. 2. The charging circuit receives power from the Magsafe and starts charging the battery if it is not fully charged […]
How does Macbook Power on
How does a MacBook power on? (For computer technicians) 1. An always-on PP3V42_G3H 3.42V power rail is created directly from an internal battery or a charger. This power rail powers the System Management Controller (SMC). The Mac is in “off mode” (G3) but the SMC keeps scanning the keyboard power-on button and Magsafe connector for […]
Intel Mac Power-On Sequence: MagSafe to Stable PPBUS_G3H
Intel Mac Power-On Sequence: MagSafe to Stable PPBUS_G3H Last updated August 15, 2026 This component-level diagnostic guide explains the early power-on sequence used by older MagSafe Intel Mac logic boards built around an ISL6259 or ISL6259A-type charger controller. It starts when a charger is connected with the battery disconnected and ends when a stable PPBUS_G3H […]
MacBook Pro graphics issues and their causes
This article is for MacBook logic board component-level repair professionals, written by IT-Tech Online, the MacBook repair specialist in Melbourne, Australia. Faulty GPUs are the main cause of graphics issues. This is especially true for the MacBook Pro 2011 A1286 AMD graphics chip. For other MacBook models, this may not be the case. Any of […]
iMac 27″ 2013 SSD upgrade
The owner did a RAM DIY upgrade from 8 GB to 16 GB with hardly noticed improvement. So he decides to upgrade the hard drive. With a Samsung 1TB SSD drive installed, the OS startup time is cut from 141 seconds to 17 seconds. Massive performance improvements! Share this: Recent Articles Get a Free Quote […]
Apple iMac Repairs | 27″ iMac 2011 graphics card replacement
27″ iMacs 2009-2011 are still very popular nowadays due to the capability, reliability and equipped with the world’s best LCD screen of the year. Unlike their little brother MacBooks where the GPUs are soldered on the logic board, the GPUs in these iMac models are soldered on the daughter boards and plugged into the standard […]
MacBook Pro Graphics Card Issue
17″ A1297 MacBook Pro 2011 GPU failed. We have developed permanent solutions to solve the problems by removing the faulty AMD GPU and rewiring the screen directly to the Intel intergraded graphics chip. We rolled out this service in January 2017 when Apple ends the GPU recall program. Since then we have done a lot […]
