Sequential Circuits Prophet-5 Service Manual - Audiofanzine

i4-11 PITCH WHEEL TRIMThis trim removes offset from the pitch wheel, so that when centered, R1 adds .OOOOV to the nriastersummers. Trimming R3129 may only be required. For complete pitch-wheel alignment:I1. Switch power off and swingout PCB 4. (Be sure to ground PCB 3.)2. Switch power on.3. For component locations, see PP331. For schematic see SD334.4. Probe P301-7 with DVM.5. Center R3129P-WH trimmer.6. Loosen pitch wheel set screw. For location, see Figure 1-4.7. With your left hand, hold the pitch wheel tight by pressing the detent with your thumb whilepushing against the exposed center notch with your second finger.8. While holding the wheel steady, adjust R1 to read +/- .05V by turning the shaft slot—rather than thewheel.9. Being certain the wheel is center-detented, tighten set screw.10. Move wheel up and down and check center-detent position reads +/- .05V.11. Trim-out residual offset with R3129.12. Repeat steps 10 and 11 for best repeatability of .000-V reading.4-12 MASTER SUMMER OFFSET TRIMThe A and B OFFSET trimmers remove residual wheel-mod offsets in the Master Summers.1. Switch power off and swing-out PCB 4.2. Switch power on.3. For component locations see PP331. For schematic, see SD334.4. Check that R2 MOD wheel is set to minimum.5. Probe U368-7 by clipping to the left end of R363.6. Toggle W-MOD FREQ A switch and adjust R339 A OFFSET for same reading (e.g. +/- mV) withW-MOD FREQ A on and off.I7. Probe U368-1 by clipping on to the left end of R360.8. Toggle W-MOD FREQ B and adjust R338 B OFFSET as in step 6.4-13 WHEEL-MOD LFO VCA BALANCE1. Switch power off and unmount PCB 4.2. For component locations see PP331. For schematic, see SD334.3. Check that W-MOD SRC MIX is set to LFO and all W-MOD DESTINATIONS and LFO SHAPEs are off4. Probe U378-13 by clipping on to left end of R3113.5. Trim R3141 LFO BALto read O.OOOV.4-10