Simple FatMan Mods Text Only Scott R. Gravenhorst chordman@ix.netcom.com Fine Pitch / Fine Pitch Offset The Fine Pitch Mod consists of simply wiring a 5K pot in series with the original 100K pitch and/or pitch offset control to create a coarse/fine system. The fine control has 5% of the effect that the coarse control has on the associated VCO pitch. When using the new system, always adjust the fine control to mid- range first. Then use the coarse control to get close, trimming out with the fine. This system allows much better control over the flange effect between the two VCO signals. I have an extra panel mounted above and below my FatMan. I positioned the fine controls directly above the coarse (original) ones on the added upper panel. An alternative approach is to replace the 100K 3/4 turn pot with a 100K 10 or 20 turn pot. This is a more expensive method, however. ================================================================= Level controls for VCO1 and VCO2 Requires 2 additional 10K pots. 1) Remove R46 and R55 from the FatMan PCB. 2) Unsolder wires H and F from the PCB and solder them to the wiper contacts of each respective level pot. (NOTE: Leave wires F and H soldered to the 1/2 MIX pot) 3) Connect a wire from each level pot low side to ground, found easily on FatMan panel. 4) Connect a wire from the PCB 'H' hole to the hot side of the VCO 1 level control 10K pot. 5) Connect a wire from the PCB 'F' hole to the hot side of the VCO 2 level control 10K pot. This is what you end up with: +------------ | V +---------------------\/\/\/\/\---+ 'hot' | 1/2 MIX | end V 10K | To PCB --------\/\/\/\/\------+ | wire H hole VCO 1 level | | | | GROUND | | | | +---------------------------------+ 'hot' | end V 10K To PCB --------\/\/\/\/\------+ wire F hole VCO 2 level | | GROUND If you turn the level pots all the way up, the 1/2 MIX pot works as before. If you want to silence one or both VCOs, use the level pots. ==========================================================