Korg Monotron Duo PCB Component Labels

     I added labels to the last of the three Monotrons, the Duo.

NJD Dub Siren schematic redraw and PCB

    I have a bit of a fascination with dub sirens. This one, the NJD, is particularly iconic. A schematic is floating around, but it's not the most pleasant to look at.

    I redrew the schematic to make the different parts more clear. You have an LFO that's a pretty standard two-transistor astable, and a main oscillator that's very similar. In between you have some LFO shaping and an LED driver, along with two buttons.

    Dials at the top select different combinations of resistors that change the oscillator rates, along with switching modulation routing. 

    The LFO is not very interesting. It only outputs a squarewave. It can be reset via switch S1 and D3. Its output goes through D4 and R22 to change C5. This gives us a slightly more interesting, uneven triangle shape. The discharge rate is set by R23 and R24. Depending on the position of S3, R24 might be switched out via R23 being grounded. C5 can also be manually charged slowly via R25 and S2 or quickly via D4 and S1.

    S4 lets you select between combinations of the square LFO and the shaped LFO as modulators for the main oscillator. It can also force the osc to a fixed pitch via D1, D2, R8, and R9.

    The main oscillator is similarly square, though the pulse width will change depending on how the two halves of it are modulated relative to each other. The harsh highs of the square wave are rounded off by the cascaded lowpass stages before the final output at R30.

 

Korg Monotron PCB Component Labels

     I've been interested in modifying a Korg Monotron. I found a labeled PCB image at Tim Stinchcombe's site here. I found the red labels very difficult to read though, so I did a little editing in Gimp. Here's the resulting image.

more legible PCB labels

Korg Monotron Delay PCB Component Labels

Even though it's old-hat, I'd like to try modifying the Korg Monotron Delay.
Korg was nice enough to share their schematic, but not the board layout. Also, the board itself isn't labeled.
I need to know what I'm working with, so I used a multimeter, and some educated guesses to draw the following. I labeled the rough sections of the circuit, so that it's a little easier to find what you're looking for. Be warned that it's not perfect, but should be a decent starting point.

Ibanez FL5 Flanger Schematic, PCB and Mod

If you look around, a lot of pedal sites describe the FL5 as a cutdown FL9. Strangely, no one seems to have a clean schematic for the FL9 or any schematic at all for the FL5.

Working off of the blurry FL9 schematic and an FL5 board, I drew up my own.

For the most part, everything is the same, including component values. The nice, matched transistors that drive the MN3102 clock have been replaced with regular, discrete transistors. "R11" and "T3" seems to be overlooked and just aren't present. The bypass circuit is a little different, but is best replaced with true bypass anyway. The biggest difference is the missing "Delay Time" pot from the FL9. I've added this back in as a daughterboard.

For simplicity's sake, I've chosen to leave out the 1/4" jacks, 9V clip and LED. Here's the result.



Eagle files are on my GitHub.

DR-110 Schematic and PCB

I'm working on some DR-110's and needed a nice, clean schematic and board layout that I can pull up in eagle. I decided to redraw the two from the service manual.

I've corrected some small inconsistencies between the schematic and board. It's mostly limited to incorrect part names and swapped positions. Also, there are at least two versions of the board, both of which have test points that conflict with the schematic. I've compromised on these.

I've routed the board so that it's very similar to the original. The audio jacks have been omitted due to a lack of proper footprints, and some tweaks have been made with the potentiometers.

Images below, .sch and .pcb are available on my Github here.