Sequential Circuits Prophet-5 Service Manual - Audiofanzine

4-14 DAC GAIN, ADC GAIN, SEQ INTERFACE TRIMThis procedure actually contains four trinns which need always be performed together and in the ordergiven.1. Switch power off and unmount PCB 4.2. For component locations see PP331. For schematic, see SD332 and SD333.3. Hit CO (lowest key).4. Probe U348-6 at TP302 CV OUT hole and note reading (e.g., +0.093V).5. Hit C5 (highest key).6. Trim R333 DAC GAIN for reading in step 4 plus exactly 5.000V (e.g., +5.093V).7. Repeat steps 3-6 until exact.8. Check other Cs. Each should be exact (e.g., 1.093, 2.093...).9. Set FILT CUTOFF knob to 10.10. Probe U360-7 at TP303 FILT CV hole just above U350.11. Trim R334 ADC GAIN to read as close to 10.000V as the 83-mV quantized voltage steps will allow.12. Patch SEQ VOLTAGE OUT to SEQUENCER VOLTAGE IN and SEQUENCER TRIGGER OUT to SEQGATE IN.13. Probe U374-1, by clipping to right end of R389.14. Hit CO.15. Trim R385 SEQ OFFSET reading to exactly half that read in step 4 (e.g. 0.093/2= 0.046).16. Select a non-UNISON program. While playing monophonically, trim R386 SEQ SCALE so Voice 5plays the same note as the other voice over the entire keyboard. (Hit key repeatedly whiletrimming.).17. Disconnect sequencer interface cables.44-15 WHEEL-MOD NOISE VGA BALANCEPCB 4 need not be removed for this trim.1. Switch PRESET off and set up controls according to Figure 4-4.2. Turn W-MOD SRC MIX to NOISE.3. Switch W-MOD FREQ B on.4. Press TUNE. When done tuning, zero-beat oscillators (Leave OSC B FINE at 0).5. With your left hand, play a key while advancing the MOD wheel until beating is heard.6. R3142 NOISE BALANCE is accessible through a hole on PCB 4 near U418. Trim out beats4-11