It seems like an eternity since I last posted a blog article so I thought this little project might be of interest. To cut a long story short, I was given a broken Boss DS-1 pedal by a client who no longer wanted it. The only information I had regarding the fault was that ‘it was dead’. This is a common description for a fault and makes for an interesting investigation into what the issue(s) may be.
A number of my clients have had their Boss DS-1’s modded by me in the past so I thought this could be the ideal opportunity to both repair the pedal and mod it.
To start with, let’s take a look at the pedal before I do anything to it.
The pedal itself is, on the first inspection, in reasonable condition; just a little dusty. The three dials turn freely and the treddle allows for the button to operate. I’m not going to take the pedal apart at this point as I’d like to see what happens when I apply power and plug a lead into the input jack socket.
Ok, so this is interesting. The pedal powers up ok. Before I go any further I’ll check what the current draw is from the pedal. If it’s high then there could be something serious going on.
When testing pedals etc I always like to use my bench power supply. I can preset the DC voltage output and set a maximum current. The power supply is telling me that there are 0.008 amps (or 8 milliamps) being drawn by the pedal right now. This is where I’d expect it to be so the plot thickens.
Ok, so the next step is to inject a known good signal into the pedal and measure what’s coming out on my oscilloscope.
Here we see that I’ve set the signal generator to output a sinewave with a frequency of 1KHz (kilohertz) and an amplitude of 0.4V (volts). This represents a typical output from a guitar.
Let’s take a quick look at how I’ve got all this set up on the bench right now.
You can see in the photo above that the signal generator (left) is feeding the Boss DS-1. I’ve plugged a lead into the output jack of the pedal and that lead has exposed wires that I’ve attached an oscilloscope probe to. On the right-hand side of the signal generator, you can observe another oscilloscope probe connected to its output terminals. You’ll see why in a moment.
When testing pedals and amps etc I like to see both the input and the output on the screen of the oscilloscope. Looking at the photo above, the trace in the top half of the screen is from the signal generator with the lower trace representing the output from the Boss DS-1. Even with pedals settings at maximum, we can see that there is absolutely no output from the DS-1 whatsoever. This would certainly explain the ‘it was dead’ description from the pedal’s previous owner.
Right, let’s get into this pedal and see what’s going on. There are a number of possible causes going through my head at this moment those being dry solder joints, failed components, internal short circuits to name but a few.
Having taken the back cover off the DS-1 I’ll give the circuit board a very close visual inspection before going any further. I’ll be checking for dry solder joints, cracks in the board, arcing, evidence of leakage from an electrolytic capacitor and anything that looks out of place. As it happens this board looked clean and tidy with nothing to really report on.
Lifting the main board out of the pedal enclosure allows for inspection of the component side. Again, nothing looks out of place, burned, broken or ‘faulty’. Looks can be deceptive though and if nothing obvious presents itself soon then I’m going to have to break out the multimeter and start probing around. If needs must then I’ve also got a signal tracer that I made a while ago that I could use but we’ll cross that bridge if we come to it.
To make inspection a little easier I’ve removed the board almost entirely now. I can take a really good look at all the potentiometers solder joints and also the jack sockets.
Another close-up of the board, mainly because this is the last photo of it before it gets modified a little later on. Before we get that far though we have to fix the pedal and get an output from it.
At this point, during the visual inspection, I’ve noticed that the output jack socket is rather dirty on the inside. I couldn’t get a good enough photo to show you sadly but there was also signs of corrosion starting. I checked the input jack socket and that was absolutely fine but given the gunk inside the output jack then that could certainly be a very good reason why we’re not getting a signal out.
I decided to replace the output jack for a few reasons. 1. The old one is gunky and not looking in the best of health and 2. I’m not a huge fan of how Boss earth some of their pedals and by using the new jack socket show above I can ensure we get a good earth connection to the body of the pedal.
I’ve included this photo to try and show the makings of a good solder joint. In the photo above we can see that I’ve stripped back some of the wire insulation, ‘tinned’ the exposed wire and then fed it through the hole in the tip lug of the jack socket. I’ve then bent the tinned wire around the lug to create a good mechanical joint. I’ll then solder this joint and push some heat-shrink over the wire and lug to complete it.
As we’re going to (hopefully) be modding the pedal soon I’ll only partially reassemble it for testing purposes. After plugging in and powering up we can see the results of the repair below.
Good stuff. What’s going in is also what’s coming out. So let’s now engage the distortion section of the pedal and take a look at that on the oscilloscope.
And we can see in the photo above that the distortion is working as it should. This is good news as it means that it was just that manky output jack socket causing us the problem and nothing more sinister. Now we can crack on with the mods
Here we can see the parts I’ve gathered to fit into the DS-1. I’ll be swapping out a lot of the electrolytic and polyester capacitors for metal film capacitors because metal film capacitors will allow for more transparency with more mid and treble frequencies to be allowed to pass. Bass response will also be improved, particularly if using a guitar with high output pickups such as humbuckers. Because this is a high-gain pedal I’ll also swap out a couple of the resistors for metal film ones as this lowers the noise floor. It must be noted that these mods are based very, very closely on famous ‘Keeley’ mods (Google ‘Robert Keeley pedal mods’ for more info after reading this article).
So here is one final look at the board before we start the modding process. You’ll see a number of electrolytic capacitors (the round black things) and also some polyester caps too (the tall(ish) white(ish) ones). These will be replaced with metal film capacitors. I’ll also be changing a couple of resistors and adding a couple of diodes for clipping the signal. The stock red LED will be replaced with a brighter blue one.
A lot of people like to use a solder sucker to remove solder from a solder joint. If there are huge blogs of solder that need removing then I’ll use a sucker in the first instance but the vast majority of the time I’ll use desoldering braid aka desoldering wick. This is a strip of copper braid that wicks away molten solder. It’s quick and easy to use and I by far and away prefer it to using a solder sucker. In the photo above we can see the underside of the circuit board, the desoldering wick and the soldering iron.
Using wick is pretty straightforward. Place the wick over the solder joint you want to remove and then press the soldering iron firmly but gently on top of the wick. The heat from the iron will pass through the wick to the solder melting the solder and allowing it to flow along the wick.
Not the greatest photo ever taken but you can just about make out the solder flowing along the wick from right to left.
In the photo above we can see that the solder has been removed from the solder joint and there is very little if any, solder left on the circuit board. There may be some residue of flux left on the board after wicking. This can easily be removed with some isopropyl alcohol and a cotton bud. I’ll continue with this procedure until all the components I’m going to replace have been removed.
Here we can see that most of the electrolytic caps have been replaced. I also replaced a ceramic capacitor with a silver mica one because silver mica is far better at handling audio frequencies and will help improve the overall tone. We’re not done yet, however.
So here are the parts that have been replaced. You can also see some off-cuts of desoldering braid in the pile. If this mod is being performed for a client then I’ll always give them the option of keeping the old parts but the vast majority of the time they are happy for them to be recycled.
So now we need to drill a couple of holes in the pedal enclosure. A small hole will be drilled in the ‘O’ of ‘TONE’ and another larger hole will be drilled next to the word ‘TONE’. If you look closely you can see where I’ve already used a centre-punch to help with the drilling. The hole in the ‘O’ will accommodate an LED that will light up when a signal passes through it and the larger hole will be used for a toggle switch.
Now the holes are drilled we can move on to the final stages of this Boss DS-1 modification.
Ok, this will need some explaining. On the original circuit board, there were two diodes that were used for clipping. This is very similar to how a lot of Marshall amps achieve their distortion and is an avenue that’s well worth exploring for modifications. Different coloured LEDs can give different results but red LEDs tend to be the most favoured. In the photo above you can see that there is a red LED on red+black wires protruding from the board and there is also a red-bodied toggle switch with an LED and red+black wires. The switch introduces an additional LED to the signal path to induce additional clipping.
So here it is. The modded Boss DS-1. We’ve fixed a faulty output jack, replaced stock parts with better quality components to improve the overall performance of the pedal plus we’ve added a toggle switch to give us further options with regards to clipping/distortion. I’ve also given the pedal a bit of a clean too. So let’s go back to the oscilloscope to make sure everything works.
Yep, the clean output from the pedal looks absolutely fine.
Again, the top trace is the sine wave from the signal generator and the bottom trace is the output from the pedal itself.
And here we can see the replacement blue LED and the red LED in the ‘O’ of ‘TONE’. That red LED will vary in brightness depending on how much signal goes through it i.e. how hard you pluck or strum. The final test involved running the pedal through an amp with a guitar feeding it rather than a signal generator. I can confirm that it sounded awesome and was a significant improvement over the unmodified pedal.
I hope you enjoyed reading this article. If you’d like to know more or if you’re considering having a pedal modified then please contact me and I’ll be only too glad to help out.