Louis Rossmann's rants, tips, and ideas on the laptop repair industry.

What is a voltage divider?

Posted Tuesday, May 5, 2015

A voltage divider is a series of two resistors one can use to lower an input voltage to your desired voltage. Let’s take the BKL_EN circuit, for example. Many circuits inside of a laptop don’t come on until they see voltage at their enable pin – think of the enable pin like their power switch. Read More

Explanation of PP3V42_G3H power line on Macbook Pro logic board

Posted Sunday, April 19, 2015

In the past blog, I discussed the onewire circuit. Here I’d like to talk about a specific power rail, that powers the onewire circuit, and its importance.   The PP3V42_G3H power rail is one of many power rails on a Macbook Pro logic board. ignore the confusing nonsense lik PPV and all that – PP3V42_G3H means 3.42v. Read More

The onewire circuit’s importance to Macbook logic board repair.

Posted Friday, April 17, 2015

If the onewire circuit does not work, the charger will only output limited power to the board, and nothing will work off of the charger. The onewire circuit depends on proper function of the battery charger chip, the SMC, and the two ICs that are utilized in the onewire lines. Common issues with the onewire Read More

BGA rework video using ZM-R6200C for Macbook logic board repair

Posted Thursday, April 16, 2015

Not relevant much anymore since Apple is covering these failed GPUs for free, but I figure it may be of interest to some how the work is performed. Here you’ll see me remove the old chip, prepare the board for a new chip, and install the new chip. This process is a bit of a Read More

What is the importance of a diode mode measurement in troubleshooting Macbook logic board circuitry?

Posted Tuesday, January 13, 2015

What makes diode mode measurements different from resistance mode measurements? Diode mode measurements allow me to quickly get an idea of what the entire circuit is doing and compare it to a known working board. Diode mode measurements are very similar to resistance measurements, but they are much faster. Resistance is measured in Ohms, and Read More

Is it right to take an iPhone 6 to Apple to get it fixed for a customer?

Posted Sunday, December 28, 2014

Apple replaces the screen to the iPhone 6 for $109. There is a lot of talk in the iDevice repair industry on whether it is ethical or not to take a phone from the customer, then bring it to Apple and have them fix it, while taking a middleman fee of $50 to $100. In Read More

Employee management 101; look for patterns, not excuses!

Posted Wednesday, December 24, 2014

From an employer’s perspective, it is important to hire people who will produce for your business. You’re going to find a lot of employees that come up with excellent reasons as to why they were unable to accomplish a task. What I suggest new employers, managers, & business owners do is avoid judging excuses on Read More

Macbook Pro 2011 GPU issues – it’s NOT the solder balls!

Posted Wednesday, October 29, 2014

I posted this to that 2011 MBP GPU issue facebook page. I figured it was worth a repost here. Another thing to set straight. Do any of you guys going on and on about how this is “improperly soldered” because it uses lead free solder realize that NO ONE USES LEADED SOLDER ANYMORE? There are Read More

Rossmann’s beginner’s guide to iPad Screen Repair.

Posted Tuesday, September 23, 2014

I posted this in response to another question on the internet a while back. I figured it was worth a repost on the company blog. a) There are no fault indications to tell whether a digitier is bad. just get the customer’s password so you can make sure there is touch everywhere. b) Make sure Read More

How to find a short in a Macbook logic board by using your brain.

Posted Sunday, August 17, 2014

Here I demonstrate one basic, low tech method to find a short to ground in a Macbook Pro logic board. I am commonly asked where I went to school to learn this, told I am a genius, etc, and I really want to demystify that. I am not a genius. I am a regular dumbass, Read More