Up/Down Switch Mod

The Up/Down Mod brings back this cool feature of the TW1 by mimic-ing the circuit. The AW2 is hardwired into the "Down" mode. In this case the bandpass filter starts with a low center frequency, rushes up to the upper frequency of the sweep, then returns back down. The "Up" mode works exactly opposite. Also, the "Up" mode reverses the Sensitivity pot throw, so make sure you mirror-mage the Sensitivity control to get the "Up" effect. This sounds much more like a Mu-Tron than the "Down" mode does. This is also a complex mod because it requires cutting traces. Proceed only if you dare.
STEP 1: Locate and cut the traces Click on this image to get a super-large blowup of the traces. You need to cut the two traces shown in the white circles. Use an exacto knife and be careful. Use an ohm meter to verify that you have indeed severed the connections in these locations. The top circle shows the cut trace from pin 5 to pin 3. Pin 3 is on the left. The lower circle shows the disconnection of pin 5 from Vhs (the half-supply bias voltage). Pin 3 needs to be connected back to Vhs, so you need to do this next using a short jumper wire, shown here.
STEP 2: Add Mod wires Click on the image to enlarge it. The 3 new wires will go to the three pins of the SPDT switch. The wires are numbered in the image. Wire 2 will go to the center pin on the switch. the other two wires will go to the other two pins on either side of the center. This will replicate the original TW1 Up/Down switch. The 47k resistor present in the TW1 is not in the AW2, and it is normally used for the "Down" position so there is no need to replace it here.
STEP 3: Wire the Switch The switch is simple to wire with the 3 wires you added in the last step. Just follow the numerical directions in Step 2 and wire up the SPDT.
STEP 4: Wire and Test Fit Wire up the switch (don't forget the heat shrink tubing where necessary. Then test fit it in the enclosure. The switch is the upper of the two switches in the image - it has no components connected to its pins. Remember, this mod reverses the Sensitivity knob!

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