As a “newbie” electrical engineer at an aerospace design company in Louisville, Colo., I have been learning the flight hardware design techniques, testing procedures and the rules that go along with troubleshooting a problem. It usually involves some extreme amount of paperwork, three signatures and highly skilled technicians trying to read through a rework or troubleshoot steps that somehow always come under scrutiny, thus making me feel like … well…. a newbie.
In the past 14 years of my career, I served as a communications repair technician in the U.S. Marine Corps, and, after I was honorably discharged, I worked at other small companies as an experienced technician using the skills I had gained in the Marine Corps. During this time, I worked part-time and used my GI bill to obtain my EE degree from the University of Nevada, Reno. While earning my degree, I spent many hours working in the aerospace field of study.
Teaching old dogs old tricks
When I moved on to the avionics group with my current employer, I was a semi-expert on sensors for micro satellites. I was proud to find my niche and felt like I could show a bit more of my knowledge without getting myself in a bind or be made fun of by my peers. And, until a few weeks ago, I never really had the right moment to “show them what I got!”
While we were working a failure on a circuit board, management wanted to conduct a destructive analysis to determine a root cause for the failure in the flight board…doing this would take time and cost a bit more than our group wanted to spend. And, at the time, the board and component failure had become the “long pole” (the biggest issue of concern) in our program and was given the highest priority.
I quietly said to my boss, “Why don’t we ‘Huntron track it?’” Based on a name-brand piece of test equipment called a Huntron Tracker, this was a term we had used a lot in my days at a fourth-echelon electronic repair facility in the Marines. Of course, my boss didn’t know about any of this, so to him I must have sounded like a “goof.”
And, my “whisper” was a little louder than I had planned and resulted in everyone at the table looking up at me in total confusion. I said quickly, “You guys know what I am talking about right? Using a curve tracer to compare a component to a known good component to look for a difference in the ‘signature’..“(Insert sound of crickets here).
Still nothing was changing their looks, so I started over with a detailed account of how I used this test equipment while a tech and how it saved us many hours trying to troubleshoot down to the root cause of the failure. Once they all were on the same page, they pointed to me to conduct the test and prepare the procedure, and since they knew no one person would have a clue what I was describing, it would be up to me to conduct the test first-hand.
For a split seconded I realized that all my years of training and experience hadn’t been for not, and that I would now be able to call on my “bag o’ tricks” without having to feel like I was talking nonsense in the aerospace world.
I troubleshot the circuit to a compare-and-hold IC that had inductive shorts to the 5 volt reference on the wrong pins - in fact it was TWO pins that had been damaged or shorted - looking closer, I realized that, during the QA inspection, the true problem was missed. On a metal can-integrated circuit, the soldering had bubbled up to the can and thus created a semi-inductive short once the board and IC were operating in a hot environment. It was so hard to see and required that the board be tilted and reviewed under a microscope, but I was able to show that the quality of the solder on this component had caused the failure. A review and circuit analysis was also conducted, and it showed that the type of intermittent problem could be traced back to this component. (Figure 1, below, the IC with shorted pins).
Figure 1: Solder Blobs! Yikes!
After I gave my full report and provided my findings, I felt like I had really come through for my team. I had several people give me a pat on the back, which motivated me to continue speaking from my experiences and show that, just because I was new to the company, I still had some area of expertise that no one else on the team had… and I felt proud to help on a problem that was given the highest priority to solve.
(William Davison recently moved from Northern Nevada to the Denver area to work in the aerospace industry after obtaining his electrical engineering degree from University of Nevada, Reno. He keeps busy with his hobbies (old BMW car restorations, LEGO Robotics and Halloween effects/costumes) and continuing his education. He is currently going to Colorado State University with a focus on obtaining his Systems Engineering Masters.
You could present interesting soldering tips to your colleagues so they could learn more about soldering techniques and not make the same mistake again. A lot of people use Huntron Tracker test equipment to determine the cause for the failures in boards, it`s good that you told them about it and saved them a lot of time.
This story is a great example of the benefit of having a team with diverse backgrounds and experiences.
The DMM vs. Huntron comment is a reminder that you shouldn't get stuck relying on one piece of test gear, but should understand what each tester tells you.
I had a similar example from working at a contract manufacturer a few years ago. One of our customers couldn't get his techs to understand that even though their frequency counter says the oscillator is ok, a distorted waveform will kill their circuit. On the other hand, we couldn't get our techs to understand that even if an o-scope shows a pretty waveform, a counter would do a better job of telling you if you met the frequency tolerance and stability criteria.
Huntron Trackers can be useful. They can also be misleading.
A few years ago a tech came to me for some help. The output voltage of a DC to DC converter was low, he had replaced the converter to no avail, and was stumped. His Huntron Tracker showed the same curve at the converter output for both the failed UUT and a good unit.
I used a DMM to quickly determine that the converter load on the bad unit was 40 ohms compared to a few Kilohms on the good unit. A load electrolytic capacitor had gone leaky and was pulling down the voltage. The Huntron could not see any difference between the good and bad capacitors. The bad one was not open and still had it's capacitance, and was not shorted either.
After that the tech believed my mantra "Never trust a Huntron". He learned how to dig deeper when the Huntron could not indicate a fault.
It's really mind-boggling to think of what my hourly rate would be if I were paid for the actual time that I spent troubleshooting a problem to get to a fix. The challenge is to avoid going down a rathole.
David Patterson, known for his pioneering research that led to RAID, clusters and more, is part of a team at UC Berkeley that recently made its RISC-V processor architecture an open source hardware offering. We talk with Patterson and one of his colleagues behind the effort about the opportunities they see, what new kinds of designs they hope to enable and what it means for today’s commercial processor giants such as Intel, ARM and Imagination Technologies.