DIY Sound Probe

When it comes to pedal circuits that give me grief, usually standard troubleshooting, solder bridge finding and "oops, I'm an idiot" admitting will suffice. In the case of my Blues Driver and Kay tremolo clone circuits these methods just aren't good enough, apparently. Both circuits function well, but have their own mysterious issues that ruin the functionality of the circuit entirely. This is why I decided I needed to construct myself a sound probe and see if that could get me anywhere closer to figuring out the problems.

A sound probe is simple enough to build. You take a length of double wire and on one end you solder on a clip for your ground, and a probe attached to the other wire. On the other end you connect the ground and probe wires to a male audio jack of your choosing, using a 100nf capacitor on the probe end, and you're good to go. I chose 6.35mm so I could plug into my mini amp. I've had some really thick car audio wire hanging around for a while, so I took about a foot of that and slapped my audio probe together. Quick and dirty, but it works.

To use the audio probe I plug it into my mini amplifier, attach the clamp to the (hopefully) grounded enclosure of the circuit and start probing along the circuit board to find the signal path. Don't forget to inject a signal into the pedal circuit first, or there will be nothing to hear. To do this I chose to play music from my cellphone and used a 3.5mm to 6.35mm adapter to connect a guitar cable between the input jack of the circuit and output of my cellphone. This all worked pretty well.

Despite having one more tool in my arsenal to help troubleshoot circuit gremlins, I'm still no closer to figuring out what's wrong with the Blues Driver clone. However, it took me posting on reddit to find out the tremolo circuit was bad from the beginning. I could go on and on about how so called verified layouts can still yield absolute worthless results, but the counter to that usually ends up being that I need to be Nicola Tesla to even touch a circuit. Reddit is a weird fucking place. Once the volume issue on the tremolo was corrected I still need to figure out why it distorts. But that's for another day.

Ugly but functional!

Velleman VTDESOL3U Desoldering Pump Review

Although far from a professional I have been tinkering with soldering more and more frequently for the last ten years. One thing that quickly became a problem was finding a proper way to remove things without messing up the solder pads, and trust me I've ruined far too many items by improperly removing a component and having the solder pad disappear completely.

For something small like a resistor or capacitor I could just heat up each solder joint and wiggle it loose, but what about things like ICs or transistors or something with short leads? That lead me to buy a super cheap desoldering pump. Very quickly I found the skill it takes to heat the solder, get right down onto the melted solder and suck it up without leaving yourself with just a tiny amount that can now never be removed is well beyond me. I feared my only alternative was a super expensive desoldering gun or pump, until I found out about the Velleman VTDESOL3U.

I had a few extra bucks in Amazon and decided to take the chance. When it arrived I plugged it in and waited for it to heat up. Mine was smoking quite a bit on first heat up, as well as mine takes quite a few minutes to fully heat up, but once it's ready to go it's well worth the investment. The tip that comes with the Velleman is a bit bigger than I'd like it to be and sadly there are no currently know alternatives, but with a little foresight you can loosen the joint, wiggle the part of the component you're aiming to desolder and suck up enough solder from the joint to make it easily removable in the end.

My first impressions with the Velleman desoldering pump were just how cheap the plastic feels, but that's only the plastic. After a few uses mine was spitting solder back out at me when I would push down the plunger. I figured it was time to check the pump reservoir, which was impossibly difficult to remove. After an email to their customer service I was advised to use a small screw driver to pry it open, and upon doing so everything worked out better than I expected.

After using the Velleman VTDESOL3U quite a bit I find it to be an amazing investment. If you can afford a professional desoldering station or gun, you may find this to be a bit lacking, but for someone who has fiddled about for years trying to find something that does exactly what the Velleman desoldering pump does, I find it to be a great addition to my tools. Small hobbyists who may not have much money, or need, to invest into a professional desoldering method would benefit greatly from this product. It's cheap, it's functional and it gets the job done.