Author Archives: ratranch

A $2 Development Board Test/Programming Jig

I’ve been using LoRa (Long Distance Radio) boards for a few recent projects. At $20 a pop, these aren’t exactly cheap. I didn’t want to dedicate one to breadboard prototyping by soldering headers to it and sought a commercial solution that would allow me to easily make a reliable temporary connection. I did not find anything like that on the market (please leave a comment if you know of such a device).

I did a bit of research and learned that pogo pins are commonly used for constructing test jigs. The downside to all the designs I saw is that they required either 3D printing parts or drilling.

I found this P75-E2 pogo pin with a diameter that can fit into a standard breadboard. But the problem is that the pins are too long and don’t stay in alignment. As you can see in the photo, my solution is to sacrifice a second breadboard by removing all of its metal clips (pry them out from the bottom) and then stacking it on top of an unmodified breadboard. Mini breadboards like these are cheap enough to devote a pair to each development board format you use.

I find that a piece of rubber electrical tape (the kind without adhesive) or a rubber band is sufficient to keep the part in contact with the board. Here is a jig for Adafruit Feather format boards with a LoRa card on top:

Why Backups Matter (even when they don’t matter)

Apple continues its multi-year assault on my beloved “late 2011” 17 inch MacBook Pro. First by shipping it with a famously defective logic board, which I learned to repair by periodically baking and now by stymying my efforts to to restore backups to it.

When the 17-incher’s hard disk started to suffer from an “invalid fsroot tree” as reported by Disk Utility, I migrated my account over to a new 15 inch MacBook Pro and started using it as my primary computer. But the 17 kept chugging along and I continued to use it mainly for designing and slicing 3D prints for my awesome Prusa MK3S.

It wouldn’t support any OS after High Sierra and occasionally I was unable to open documents but the laptop performed well enough for its current purpose.

All the work I was creating on the 17″ Mac was either one-off stuff or stored in the cloud. So I saw no point in wasting storage and backing the laptop’s increasingly corrupt file system. When the time came, I would just reformat or replace its SSD and restore from the 15-incher’s backup. Easy peasy.

So the day finally came when ‘Ol Seventeen just kept crashing and I replaced it’s 1 TB SSD with a 2TB disk. I fired it up in Internet Restore mode (Command-Option-R), formatted the SSD, and installed High Sierra.

So just use Migration Assistant to restore my account from a Time Capsule backup, right? Nope, that didn’t show any valid backups to restore from. No problem, I could use Migration Assistant to push the account from the 15-inch to the 17-inch, correct? Um no, Apple wouldn’t have any of that either.

Backups from the 15″, which is running Catalina, could not be migrated to the older High Sierra OS. So instead of restoring my account the easy way using Migration Assistant, I will need to manually copy my stuff over from the 15″, reinstall applications, re-set preferences, re-enter passwords and all that kind of fun stuff. Uck.

So don’t assume that the migration tool that makes it so easy to move from an old to a new Mac works the other way around. In retrospect, I can understand why this isn’t just a diabolical plot to get me to buy another new Mac. There’s no practical way for an OS to know what incompatible applications, features or documents could be added in future operating systems, so no way to determine what stuff is compatible and what isn’t. Lesson learned.

Reflow Madness

Over the past several months, I did a few more reflow repairs with my trusty heat gun.  I successfully resurrected a Beats Pill bluetooth speaker but it failed again after a few weeks.  Another Pill is still working okay.  I rescued a 15″ MacBook Pro with video problems but had no success with a 17-incher.

Meanwhile, my own 17″ MacBook Pro, which had been limping along with disabled AMD graphics (thanks to Cody Krieger’s excellent gfxCardStatus menu bar app), went fully dim after a reboot.  This was my excuse to hang up the heat gun for good and invest in a cheap Chinese reflow oven.

At $369, the Happybuy Reflow Soldering Machine is very cheap for a reflow oven but pricey given its design flaws and build quality.  The oven I purchased is an example of the T962A design, which is produced by several different manufacturers.  Google “T962A” and you’ll find various hardware fixes as well as improved firmware.

As shipped, the T962A is both unpleasant and dangerous to operate.  At this stage, I’ve made two modifications that should be considered mandatory

The first problem is that the metal case is not properly connected to ground, posing the potential risk of electrocution!  This is a widely known (and easy to fix) issue.  I’m amazed that units with such a serious defect continue to be shipped.

The second problem is that a heat shield is secured with what appears to be paper masking tape.  It produces noxious fumes and smoke when the oven heats up.  This is also easy to fix by replacing the tape with Kapton tape.  LOL, on Amazon the oven and tape are “frequently bought together.”

There are other fixes available to improve the UI and performance that I haven’t bothered with.  After fixing the ground and tape issues, the oven performs fine for repair work.  I use profile #3 for lead free solder.

To date, I’ve had one success and one failure with the oven.  I wrecked the aforementioned Beats Pill by melting the line in and out jacks.  These are apparently installed after the SMD components are reflowed.  On the other hand, my ailing MacBook Pro was a complete success.  Time will tell if this repair lasts longer than the heat gun fix.

Nuvico HDocs Mobile HD app stopped working

Here’s a quick one for anybody with a legacy Nuvico HD-TVI security DVR, e.g.,model DT-E800.  The iOS app stopped being updated in 2014 and doesn’t work with iOS versions 11 and later.  My user was ready to ditch his perfectly functional DVR because of this.

Long story short, a little reverse engineering revealed that the Nuvico platform is identical to another DVR branded “Hikvision”.  And Hikvision has a current app that is a drop-in replacement.

Replace HDocs Mobile HD with iVMS-4500 lite.  You’re welcome.

Resurrecting a 17″ MacBook Pro with a heat gun

So the dreaded day came when my beloved “late 2011” 17 inch MacBook Pro died.  The screen wigged out while it was in use, then it would only boot halfway before stopping at a gray screen.  From experience, I knew that it was suffering from the dreaded AMD GPU logic board failure.  What commonly happens is that the solder joints in or around the GPU daughter-card fail over time, resulting in a gray, blank or garbled screen.

Ordinarily I would not attempt to repair any board with solder failure but new logic boards are simply not available for the late 2011 models and used ones are absurdly expensive (and may be close to failing anyway).  The repair I describe below worked perfectly for my 17 incher and also applies to the 15 inch models from the same era.

Best MacBook Pro ever?

IMHO, Apple has never made a better laptop for the the specific use case scenario where some limited portability is required and screen real estate is more important than size/weight.  This was the last of the 17-inchers, perhaps forever, and I plan to keep using it until it is pried out of my cold dead hands.  Okay, the last part is a bit of an exaggeration but my MBP does everything I need it to do and is still plenty fast.  Over the years I’ve managed to keep it ticking by upgrading to 16 GB RAM–Apple only officially supports 8 GB, but this works just fine thank you very much–and a 1 TB SSD.

Several people suggested that I should just put the old relic out to pasture and update to a new 15″ MacBook Pro.  “You can fit even more stuff on the new 15 inch screen!” they say.  Indeed, the 17-incher’s 1920 X 1200 pixel native resolution seems puny compared with the current 2880 X 1800 px Retina display.  But my eyes ain’t what they used to be and cramming my workspace into 15 inches just makes everything too darned small.

Non-intrusive repair option

Anyway, back to the repair.  The least intrusive way to make a MBP with GPU failure operational again is to disable the AMD GPU via software.  The built-in Intel GPU will take over but video performance for demanding tasks would suffer greatly.  I use my laptop for photo editing so that wasn’t a viable option.

Logic board repair options, from conservative to crazy

The other common fix is to reflow the solder in and around the GPU by using a heat source.  Multiple techniques, ranging from reckless (and cheap) to professional (and expensive) have been applied, with mixed success.  I hit the web to see what worked best.

During my research, mainly on Youtube, solutions included:  bake your MacBook in the kitchen oven at 350 degrees for an hour (like a cake?), disconnect the fans and leave it running and wrapped in blankets for a couple of hours (so snug and warm), open the bottom cover and hit the logic board with a hairdryer until you smell stuff melting, or (yawn) remove the logic board and put it though a programmed heating profile in an expensive professional reflow oven.  This video was one of my favorites.

So lacking a reflow oven but wanting to be halfway scientific about doing the job, I decided to reflow the GPU using a common hot air gunThis video does a good job at demonstrating the technique and is pretty close to how I did it.  The time/temperature points I chose are a little different based on my review of lead free solder reflow oven profiles, with times and temperatures increased slightly to compensate for hot air heating inefficiency.

Hot air reflow procedure

Note that all temperatures are specified in degrees Centigrade.

  1. Disassemble the MacBook Pro, referring to an online guide like those on, and remove the logic board.
  2. Clean all thermal paste residue off the CPU and GPU, using thermal grease solvent, flux remover, methanol or any other PCB-friendly solvent that works.  Just please do not use rubbing alcohol. It contains water and could create some new problems.
  3. Create a mask for the GPU using two or three sheets of aluminum foil.  You’ll want to cover all of the logic board except for the GPU.  Don’t install the mask yet.
  4. Place the logic board on a heat proof surface.  With your heat gun set to high and held a couple of feet away, heat both sides of the logic board for a couple of minutes to around 100° C.  The temperature isn’t really critical at this stage. The goal is warm up the entire board, but not so much that it cannot be handled by its edges.
  5. Attach the aluminum foil mask that you made in step 3.  If you are using a thermocouple for temperature measurement, affix the end so that it is resting on a corner of the GPU.  (I used a Fluke multimeter with a Type K thermocouple).  An infrared thermometer also works great;  keep it aimed at the middle of the GPU.
  6. In the subsequent steps, stay as close to the recommended times and temperatures as possible.  If your heat gun has high and low settings, select low.  Hold the heat gun about 3 inches from the GPU, moving it closer or further as necessary to hit the temperature targets.
  7. Apply heat until the surface of the GPU reaches 200° C, then continue applying heat for 3 minutes, keeping the GPU at 200°.
  8. Slowly increase heat to 220°, no more than 3° per second.
  9. Hold at 220° C for 2-1/2 minutes.
  10. Increase GPU temperature to 290° C and hold for 1 minute.
  11. Slowly back away the heat gun, decreasing heat by no more than 6° per second until you reach 200°, then turn off the heat gun and allow the logic board to continue cooling to room temperature
  12. Apply new thermal paste to the CPU and GPU, reinstall the heat sink and reassemble the laptop.


So far my success rate with this process is 100% 🙂  During my web research, I saw several comments indicating that this repair should be viewed as only temporary because the original design is flawed.  But if it my trusty 2011 17″ works for another six years, I’ll be more than satisfied with the couple of hours time invested in fixing it.

This repair was performed in March 2018 and I’ll make a follow-up post if the same failure occurs sometime in the future.

Update – December 30, 2018:  The repair only lasted for nine months before artifacts started appearing again whenever the GPU was activated.  At this stage, I had already shifted to a new 15″ MacBook Pro as my main computer and relegated the 17-incher to my workshop, where it is mainly used for slicing 3D prints.  The GPU’s improved graphics performance has no benefit for this application.  Integrated graphics work just fine.

Instead of spending half a day performing another heat gun repair, I installed Cody Krieger’s excellent gfxCardStatus menu bar app to permanently disable the GPU.  gfxCardStatus is free and open-source, but please consider giving Cody a generous donation if you use his app to extend the useful life of your $1500+ laptop.