A recap of our progress so far is in order. We have traveled a lot of ground in the project and sometimes it is easy to loose track of the goal. A simple addition of an external 9VDC jack turned into a pot core inductor engineering and fabrication project. Not to mention, we still haven't addressed all the other wiring issues this pedal has. But, I digress..
If you remember, my buddy Greg wanted me to complete his retrofit of a 9VDC jack so he could power his Colorsound Fuzz+Wah from his pedal board. I got into the pedal and found that it was a bit of an odd ball. The examples of the Fuzz+Wah I was finding on the internet didn't really match what I was looking at. The case was completely different and the schematics didn't match up either. I was able to find one that was for sale but it had no documentation available. I looked at the circuit and found that a footswitch and input connector were broken and the wah section didn't work at all. I found that the inductor lead had broken due to a misguided preventive maintenance. The wires inside had become very brittle and broke off with just a touch.
I needed replacement parts and found that the footswitch manufacturer was out of business. A guy in England is making inductors as part of a reproduction wah for a contract he has with the folks that own the Colorsound name. He can't sell parts due to his contract. So, I am snubbed on all sides for parts. Time to get cleaver and ambitious.
I have to hand wind the replacement inductor to get these repairs done.
The first thing to happen was to find a manufacturer of pot core ferrites and plastic bobbins. That wasn't too hard. Magnetics, Inc. is one of the largest and oldest manufacturers out there. Their selection and design materials were very helpful and I was able to arrive at a selection in short order.
The next issue was to find a stocking distributor that would sell small quantities. I decided I would go with 10 units. Hopefully, that would give enough for mistakes, accidents and experiments and I might end up with 2 or 3 working units
Magnetics, Inc. listed several distributors on the website and I picked Dexter Magnetics and found they stocked the items I needed. These folks are used to dealing in large quantities (1000s) and don't have on line ordering. You must ask for a quote and work out the details on the phone or in emails. Most will sell small quantities if you are producing prototypes and they will take credit cards.
OK, parts sourced and on the way. I ended up spending about $75 on parts, not including the 40AWG wire.
Now it occurs to me that I have to hand wind 485 wraps of REALLY thin 40awg wire onto a tiny little bobbin. OK, that ain't gonna happen. I looked all over the internet and found some cleaver, and expensive solutions to wind an inductor bobbin.
Ebay provided a solution. For $45, I bought this little gem to help me out. It is setup to handle large bobbins so I had to modify it to accommodate the tiny bobbins the pot core inductor uses. The best feature is the turns counter. Pretty handy when you have 485 turns to keep track of.
I had to drill a clearance whole in the center of the shaft for an 8-32 screw to hold the bobbin on. It isn't massively scientific but it worked. The wire I am using is 40awg which is as thin as a human hair. It breaks really easily with too much tension. There were a couple of hiccups using this winder. The counter would get stuck and I didn't notice so the number of turns were unknown. It took a few tries to get everything lined up and working.
It isn't perfect but it gets the job done well enough and perhaps adds that mojo by producing a unique inductor every time.
The finished product being measured with an LCR meter. It is a good idea to bond the two pot core halves together with a little cement. The manufacturer doesn't come out specify how or what to use. I took that to mean that it isn't critical. I applied the cement on the outside of the package rather than on the rim. I did notice that spreading glue on the rim so the two halves bond there increases the air gap and messes up the inductance.
Next time, I install the inductor, check the circuit boards and tackle the footswitch and DC wiring. It was a long way down into this rabbit hole but I think we are headed up and out...