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[Guitar Pedal Mod] Crybaby wah wah - True Bypass on old model
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06-03-2011 3:00am#1Lately I've been browsing around various modification / custom build sites and reading up about how to mod effects pedals. I was originally thinking of building a BYOC Mighty Mouse but I had also read up on wah mods, and when I saw a Crybaby on adverts.ie for €40 well I almost bit the guy's hand off.
Long story short, when I opened it up and had a look inside, it wasn't what I expected. It had a few differences from the pictures and diagrams I'd seen online and I wasn't sure exactly what I had. I had to dig a bit to find out that it was a Revision C or D model from 1990 or before. (Can I call that vintage at this stage?) The PCB says revision C but it has a jack socket for external power, which the Dunlop site says was introduced in revision D in 1989.
The mod I had been looking at was the Foot-on-pedal / True Bypass mod by Koen Bussemaker on Instructables http://www.instructables.com/id/Foot-on-pedal-True-Bypass-crybaby-wah-mod/. But I couldn't find any information on how to do this on a Crybaby with the jacks separate to the circuit board. Nothing for it but to figure it out myself.
I found a circuit schematic online at http://www.montagar.com/~patj/crybaby.gif (Edit: found the address of this schematic) and traced through the actual circuit to figure out how it matched up and what all the wires were for. The only differences were that mine has two .22uF capacitors instead of .01uF. (I read elsewhere these specific cap value changes are a feature of the Hendrix signature model) This version has a loom that connects up to 10 wires to the PCB. Figuring these out was the key to doing the mod successfully so I took my time.
I ordered switches from an eBay seller in Hong Kong, the LEDs I salvaged from an old PC that I had in the attic, and I bought two resistors and two trim pots in Maplin in Galway. I replaced the Gain and Q resistors with the trim pots a week or two ago and I was happy with the results.
to be continued...Tagged:2
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The switches arrived yesterday, barely a week after I ordered them. Fair dues to the eBay guy and the Chinese postal service!
I got stuck in this afternoon. The first thing I did was to de-solder the old switch (SPDT) and unscrew it. I didn't put in the new switch (3PDT) yet, I decided to drill the holes first and I didn't want any stray swarf getting near it.
Two 3mm holes at the front for the LEDs, strategically placed so the white plastic holders that came with them would not foul off the battery. I decided to put the LEDs at the front instead of the side so that I could see them from different angles when playing. I tested with the holders in place (minus the LEDs) in between the battery and the chassis and they fitted but it was tight.
A 5.5mm hole in the foot pedal for the push switch (DPDT momentary), between the A of amplifier and the I of instrument as mentioned on Instructables. The rubber around this hole also needs to be removed to make just enough room for the cap to go on the push switch. A 5.5mm hole on the right side towards the back for the toggle switch (3PDT). I used a brass bit with plenty of 3-in-1 oil and the pedal gripped in a vice. Another 5.5mm hole in the top of the casing just in front of the pot hole to thread the wires through. I sanded the holes off with a dremel to remove rough edges. I also wore goggles like my old metalwork teacher always insisted. The chassis isn't actually steel, it's a non-ferrous alloy which is much easier to drill through.
I then screwed in the new stomp switch and the toggle switch and let the soldering iron heat up. I took four wires of different colours and threaded them through the hole, then stripped and twisted the ends, tinned them and soldered them to the push switch. There's also a jumper wire that runs across two of the pins. I When the whole job was finished I noticed there was a design flaw in the way I put it together, The solder joints at the push switch are constantly being dragged up and down as the wah pedal is in use. I need to go back and revisit this, probably replace the 4 wires with longer ones and fasten them to the underside of the foot pedal with a loop between the fastening and the hole to take the stress away from the joints.
Next I pushed the LEDs into position, tested them with the 9v battery and 330 ohm resistor to make sure they were the right way around, and then superglued them into place.
to be continued ...0 -
So next came the wiring. I started with the LED circuit and then wired up the bypass part.
This involved desoldering a few connections on the input jack and the pot and running new wires through the switches. If I get organised enough I'll do a nice graphic for this, otherwise you can see it on the handwritten design here:
After the LED circuit was soldered in I tested it and was happy with the result. When I did the next stage I made a mistake and wired the toggle switch the wrong way around. That meant the LED and bypass controls were out of sync. Rather than desolder and replace 4 connections I swapped the two lugs of the LED connection which were easier to access.
And then it was time to try it out...
Definitely happy with the result, apart from the weakness at the push switch I mentioned earlier. That'll be a PITA until I fix it.0 -
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