Hard-to-find faults and other homebrew ‘Gumption traps’

I recently cut this small piece Veroboard to hold two vertically aligned miniature potentiometers on a receiver front panel. The three soldered tracks to the right allow connection of the audio signal to the volume control using shielded twin conductor cable. Very standard stuff, I’ve been wiring up audio amplifiers to volume controls like this for about four decades. But this one wouldn’t work. It has a fault — it’s there, in the picture above, right in front of your eyes… can you see it?

Rotating the potentiometer shaft didn’t reduce the volume and the whole thing motor-boated at full throttle. After checking, re-checking and re-re-checking I could find nothing wrong. So I pulled the audio cable off and soldered it to a different potentiometer. It worked.

Putting the meter on the Veroboard tracks revealed the nature of the fault. The ohm-meter test showed that the left-most and middle (wiper) pins were shorted. Faulty potentiometer? No. Look closely…

A tiny residual copper flashing left behind by Vero’s manufacturing processes was shorting two adjacent tracks. So tiny I never would have found it without a good illuminated desk magnifier. After photographing it on 8x zoom, two or three passes with a jeweler’s screwdriver cleared it, and the receiver audio volume worked perfectly.

No criticism of Veroboard intended whatsoever, it’s a fine product that I’ve used since boyhood, rather, this story provides an insight into the wonderful and varied situations that can lead to a homebrew radio or electronics module not working. The short could have been due to any number of more common things — a solder bridge, a component lead too long, an iron fragment from the workshop bench.

In most every case, the process for diagnosing something like this is one of ‘divide and conquer’. With a big dob of patience.

In this situation you have a few allies… your recollection of what has gone before, your ability to isolate things, and above all, you mindset.

In my case, I knew that this audio chain had worked with before, with a different potentiometer. So I knew I had introduced the fault when I removed the original potentiometer and connected into the Veroboard assembly. That’s my recollection of what went before coming into play.

Swapping the original one back proved that the fault was indeed on the new Vero assembly. Soldering the original potentiometer onto the new twin conductor shielded cable proved that the new cable and its connection to the board was working. At that point, the fault was isolated to the new potentiometer or the board. That’s my ability to isolate things coming into play.

Hurdles like this test the attitude more than the skill of the maker. Most beginners could have diagnosed shorted circuit board tracks with a multimeter. But often, logic of a situation falls away to other illogical ‘human factors’, masking the obvious and clouding the maker’s judgment.

The most common forces behind these human failings are fatigue and doubt. When a simple PCB short occurs deep inside something complex like an amateur superheterodyne receiver or transceiver, or on an evening when the maker is anxious to get the project working, or who is starting to feel some doubt about their personal ability to complete the project, little things become bigger things. This is what writer Robert Pirsig called a ‘gumption trap’.

In Zen and the Art of Motorcycle Maintenance, Pirsig used a motorcycle journey across America with his son and another couple as the setting for an exploration of what ultimately became known as the ‘Metaphysics of Quality’. Its heady stuff, but it includes some profound reflections on the relationship we have to the things we design, make, use and repair.

In the ZAMM narrative, Pirsig maintains his own older bike as he crosses California, while his companions use their new bikes like appliances. Pirsig develops a one-ness with his motorcycle that the others do not experience. He thinks deeply about the communion between man and his machine, and the freedom of movement that his well-maintained motorcycle gives him. The state of flow that he feels when he is on the open road, and he and his machine are working at their optimal performance, he calls ‘gumption’.

But this state of ‘flow’ is easily broken. The things that jar him back to the state of compromised existence of our messy real-world existences he calls ‘gumption traps’. His motorcycle maintenance becomes a quest for ‘quality’ which he strives to achieve by studying the intricacies of the parts of his machine, and by anticipating and taking steps to avoid gumption traps of all kinds. Although I’ve never done any, it seems that motorcycle maintenance has a lot in common with using, making and repairing your own radios.

Pirsig’s intimate knowledge of his machine and its limitations becomes a metaphor for knowledge. His antidote to the brokenness of his old cycle, and the world, is a systemic evaluation of his patterns of thought. He cultivates his sense of patience, care and attentiveness to what he is doing, forging a sense of harmony with the action at hand. In these moments he finds a peace of mind which creates a positive reinforcement loop.

“…right values produce right thoughts. Right thoughts produce right actions and right actions produce work which will be a material selection for others to see of the serenity at the center of it all.”

In finding his groove, he finds himself.

“The real cycle you’re working on is a cycle called yourself. The machine that appears to be ‘out there’ and the person that appears to be ‘in here’ are not two separate things. They grow toward Quality or fall away from Quality together.”

Enough literary criticism. This post started with a Veroboard short and has ended up in Metaphysics. We are amateur radio makers and experimenters, not amateur philosophers or monks!

But we all want that sense of flow, whether we are repairing a motorcycle, programming a computer, or soldering components onto a board. There are as many gumption traps in the shack as in the workshop. Many are more obvious than a track bridge that can only be seen under a microscope. Some are much more obscure.

The important thing is to be conscious of your own state of mind when you are immersed in your making. Knowing when to take a break is vitally important to maintaining your gumption. We homebrewers spend a lot of time at the shack bench melting solder. It’s your personal recreation time, so use it to work on yourself while you work on your rig.

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