Having built the Fuzz circuit – I now need to test it. The instructions from Jed’s Peds stress just how important proper testing is – although it’s pretty obvious really. The prospect of building and integrating an FX circuit board into a guitar’s on-board tone circuit is already (potentially) problematic enough, as it is. It would be plain daft to get into building the rest of the circuit, without checking the Fuzz first.
Although I’ll be eventually using the circuit board in a slightly different context to the one it was originally designed for – (onboard a guitar, with a 9V battery pack and a remote push/pull control pot) – the instructions cover a particular step-by-step methodology, which uses a simplified “stomp box” configuration. Since this is my very first circuit board build – it makes perfect sense to follow their exact lead, and then work out how to modify the connection once I’ve checked the circuit works. The only difference being that I’ll use a 9V battery clip, instead of the supplied 9V power supply adaptor socket.
The instructions have a picture which shows the test circuit completed – but I found the written step-by-step walk through to be much more helpful, in identifying exactly what each wire does, and where it connects to. It somehow helps you understand the circuit a little bit better – rather than just slavishly “joining the dots”.
First – the input and output jack sockets are prepared by tinning each of the terminals. Then – a short ground wire is connected to each of the negative, (-ve), “barrel” terminals. The circuit kit comes supplied with just barely enough plastic coated wire to complete a stomp-box installation, although I think I’ll eventually need more to successfully build the board into the little rout under the Stratocaster scratchplate here – (leaving sufficient “slack” at the ends, to facilitate removal of the plate for periodic maintenance). I use regular, cloth-covered push back wire instead. I’ll also eventually be using a single stereo jack to facilitate both output from the guitar, and power switching for the unit – so after testing – these two sockets will ultimately end up in the spare parts box.
I’d originally planned to use a battery clip hidden within the tremolo spring compartment at the back, to power the FX board. However – those plans were formulated long ago – before I decided to put the original concept on ice, (read some of the other earlier posts on this build, to see some of the previous journey here…). Unfortunately – it was so long ago, that I’ve now completely misplaced the original battery clip I purchased. In fact – in the interim – I’ve lost both it, and it’s replacement. After a bit of a re-think – I’m now going to go with a regular clip-on battery cap terminal, and will eventually secure it in place with a simple Velcro cable tie.
(Later on – if everything works out well – I may make things a bit more “permanent” and take a look at one of these Fishman 9V battery packs. The USB rechargeable packs are specifically made to power Fishman active pickups – but they can also be modified to provide a constant 9V charge for other devices. There are options for other types of guitar available too – but the Stratocaster-specific unit has a low profile, and simply replaces the normal tremolo spring cover. With one of those in place – it’ll almost look like I planned the whole thing all along…)
Another black, cloth-covered, push-back ground wire is soldered into the “G” output terminal on the circuit board. There are now four black ground wires. One from the board, two from the two jack sockets, and the one from the battery clip. The ends of these four wires are stripped, (or pushed back) – with the cores twisted together and soldered. It’s a messy, ugly connection – but effective. This completes the temporary ground network for the circuit board.
Next – the red wire from the battery clip is soldered into the “V” output terminal on the circuit board. Finally – two different coloured plastic wires from the FX kit connect the marked input and output terminals on the board, (“IN” and “OU”), to the relevant positive (+ve) “tip” connections on each jack socket. The jack socket which is connected to the “IN” wire becomes the input socket for the test circuit. The socket which is connected to the “OU” wire becomes the output socket.
I’ll use a Fender Mustang Micro amp connected to the output socket, and a set of headphones to monitor the output signal. The Micro amp is set to a preset which provides a clean, ulfiltered signal – and all EQ/Effects/Mod settings are set to “off” or “bypass”. A guitar will be connected to the input socket via a standard lead to provide an input signal. To power the circuit – I have one of those crappy 9V batteries which come with every remote control you’ve ever owned. These never seem to be up to the job to power much else for long – so they always get shoved to the back of a drawer, and forgotten. I don’t know how old this one is, and I’m not even sure it’ll retain enough “oomph” to power this simple affair. But no point wasting a perfectly good, new, Duracell on a simple test like this…
…Now we can all laugh about this – but bear in mind that this is the first time I’ve ever put a circuit board together, and I’m also improvising a little from the given instructions with the power supply and the offboard control pot. More experienced fettlers among the readership will immediately notice why I didn’t happen to get a signal out of the test circuit, as shown in the image above – but I’ll confess it left me completely stumped at first. With everything connected up – if not a clear fuzz – I’d at least expected a hum, or some kind of scratchy sound… but the circuit appeared to be absolutely dead.
My first thought was that it was the battery – so that fresh Duracell eventually ended up getting used after all… Still nothing. In such a case, the instructions advise going carefully over the board and the setup – checking each solder joint until the problem is found. It also recommends taking a break – rather than hurrying into changes. Good advice… I took a break, and thought about something else for a bit. Eventually – it became laughably obvious. I hadn’t connected a control pot – and the three unconnected wires for the control are all part of the circuit. An incomplete circuit will always respond as if it’s completely dead – since there is literally no circuit…
… I connected a standard, short-shaft 500K CTS pot – checking that each wire connected to the correct terminal, according to the instructions. Then – I clipped in the battery, hooked-up the guitar and the micro amp, and repeated the test…
IT LIVES!!… Through the micro amp and the headphones – it sounds a bit like a bee caught in a bottle – but it’s clearly a Fuzz, and the control pot attenuates the signal, (although the audio taper does compress the useable range of control into something less than half a turn. I wonder if a linear taper might be better?…). It appears I can just about see well enough to wire a simple circuit board. Now to build the rest of the guitar tone circuit, and to work out how to fully integrate the Fuzz under the “bonnet” of the Strat…
Garageland 