Repairs: Ibanez FL9 Flanger

Since I don't get much time to play guitar these days and when I do, it's generally just guitar and amp. My FX don't get used too often, and the least often used of my FX would have to be my Ibanez FL9 Flanger. Generally I don't havemuch use for flanging effects. It's fun and all, but I prefer to use it sparingly. If I'm going to use a modulated effect, it's more likely that I'll use a phaser. Just personal preference.

Because of this, my FL9 sat in a drawer for the best part of a year. It's an old pedal (over 25 years) and the last time I went to use it, it just passed a clean tone. The pedal wasn't toally broken, the delay chip was still working as there as a bit of a flange sound when twiddling the controls. Upon opening it up, some of the jooints looked cold. So I proceeded to re-solder everything on the board. No go. It took a  while to track down the schematic (didn't end up using it), but I'd read a snippet from one forum about replacing old electrolytic caps, so i figured that i'd give it a try. I went over the board and documented everything electrolytic.

There were two caps near the middle of the board which weren't coloured blue like the rest (they were orange), so I decided to replace them first and give it a test (I'd seen a similar arrangement on a synth I'd built). My hunch was right, they were there to control the LFO rate. The LFO was working again, but the effect was very subtle. Not at all like I remembered.

Fortunately the board has three trim pots for adjusting various biases. Ignore the middle one, it's there to bias a transistor and the factory setting is just right to avoid unwanted and unpleasant clipping. The trim pot closes to the middle controls feedback and the one further away controls depth. With these two trim pots you can get the pedal to self oscillate. Particularly with the first one. It's not a sound I'd want all the time, so I've set it up to kick in at about 70% maximum on the front panel feedback knob. The mod is safe and easy to do. You won't even need to take the board out to do it. While increasing the feedback makes the flanger more prominent, it still falls short of being a true "jet" flanger. Still it is nice to have in the tool kit.

FL9 Service Manual Page 1

FL9 Service Manual Page 2 (Schematic)

FL9 Service Manual Page 3 (Trouble Shooting)

FL9 Service Manual Page 4 (PCB Layout) - LFO Caps Highlighted w/red box.

Re-Repair & sound sample.

2010 - Behringer DC9 Compressor

The humble compressor.
An oft misunderstood, yet incredibly useful device.

I have two of these MXR clones. One modded, one stock.
Like the original, the stock version filters out a bit of bottom end, which gives the perception of a treble boost.
Modding it to get some bass back is as simple as adding a .1uf cap in parallel with the input cap. You don't even need to pull the PCB out to do the mod either.


I have a few different uses for these pedals.
One of them is to add a master volume control to my Peavey Delta Blues, via the FX loop.
The amp is far too loud for my flat. Actually even a 5w Valve Jr is too loud for my flat, but I can't do much about it. The Delta Blues on the other hand can be tamed.

Adding the modded CP9 to the FX loop and reducing the sensitity to minimum gives quite a bit of control over the volume of the amp. It's easy to get the clean preamp distorting at maximum volume, while still having good standing with the neighbours! If you need to add a little compression, it's just a turn of the knob.
This is especially handy in the FX loop after the Line 6 M13, which has compressors built in, but they don't reduce the overall volume nearly as well as this bargain basement clone.

The CP9 is also incredibly useful for driving a DI before a mixing desk when recording Bass.
It adds Volume obviously, but also allows the Bass to sound more controlled and clean into themixing board, perfect for manipulating with your favourite bass amp modeler.

My main use for the CP9 is actually something not really music related, ans certainly not for performance.
I use them in stereo to control the volume of my television!

That's right I'm using them on the TV and now I no longer have to put up with being blasted out of my chair by overly loud commercials or having difficulty hearing dialogue when the volume of the hifi is set to a sensible level for watching action movies.

Since there may be problems with impedance on some consumer devices, I recommend the addition of a simple circuit on the input. The unmodified pedals were fine with a DVD player output, but when it came to the TV output I was getting some strange noises due to mismatched input/outputs.

All that needs to be done is a 22k resistor in line with the positive lead and a 1k resistor from the positive lead to ground. This drops the output impedance of the TV to something that the pedal can handle and improves frequency response as well as noise rejection. I actually got the idea from one of Ken Stone's circuits, the Stomp Box Adapter V2.

I'm certain this mod would work on just about any pedal if one were inclined to mess about with processing the TV. that's why I just built it into a black jiffy box with sockets to plug into whatever I want. It's also useful for dropping Keyboard outputs to be used by the pedal (it's original intent I believe).

2010 - Boss SD-1

This one came to me nice n' cheap. I bought it at a 2nd hand dealer in the city. $65 and practically brand new.
What do you do with cheap pedals? Mod them of course!

I'd read that this is basically a tube screamer with some parts changes.

Stock this pedal is pretty decent sounding, a moderate overdrive on full and a nice clean boost on minimum.
Unfortunately the filter caps on the input remove a lot of bottom end. So rather than add some punch, it cuts some of the guts out of it.

The first thing I did was to do the SD808 mod and turn it into a tube screamer.
Basically it's just changing one cap, removing another as well as a diode in the clipping stage.
What this does is make the clipping asymmetrical and alter the tone control.
To my ears and playing style, it wasn't much of an improvement. It still lacked the bottom end.

The next mod I did was the bass mod.
This is done by simply bridging two components, a capacitor and a resistor.
It was three weeks before I got around to testing it out, but when I did, the pedal was a whole new beast.
The gain still isn't much really, but that's OK I like it like that. The bottom end is nice and big, though a little muddy as there's a slight octave effect on some notes. But for the tone I'm after, this is almost perfect.

Placed in the FX loop of the Delta Blues, the pedal is responsive to dynamics and has the added bonus of acting as a master volume, though the extra gain from the preamp means that the pedal never completely cleans up.

I may end up doing some further mods to the clipping section and maybe change out the opamp for something else. But for now I'm pretty happy with this cheap pedal that cost about $1 and 15 minutes of my time to get close to what I want out of an overdrive.

Not too smooth, and just a little raspy.