Polaris Service Manual: Adjustments and Checkout
This section outlines both hardware and software adjustments. The hardware adjustments involve measurements which require a reference ground. The main ground test point is located on the main PC board below Z63, just to the right of connector J14. This is a fine reference for troubleshooting digital circuits, but when checking a supply, especially for noise, use the actual supply reference ground. Stay away from the ground side or filter capacitors, because of the heavy currents, and from chassis ground, which is isolated by 1M ohm. Long ground leads pick up extra noise; use a local ground from the shielded scope probe instead.
Digital +5V Level
Prior to any adjustments load the supply by pressing LOWER FUNCTION - D - 3. Measure the +5V digital level between P3 pin 3 (orange wire) and pin 2 (red wire). Adjust R9 for +5.00V (the tolerance is 10mV). Check to see that all 60 LEDS are lit. During normal full load operation the noise level on the output should be approximately 20mV P-P. The ripple on the input to Z5 should be about 1.25V P-P at a DC level of an unregulated 13V. Since this is a full wave supply, the ripple frequency should be 120Hz. (having a period or 8.33 msec). Press LOWER FUNCTION to return panel to normal operation.
Reference +5V Level
Measure the +5V reference between P4 pin 1 (brown wire) and pin 6 (blue wire). Adjust R5 for +5.00V to within 10mV. The noise level on this output is normally about 1mV P-P; too small to be seen through the noise picked up from the air by most scope probes. The ripple at the input to Z1 should be approximately 2V P-P at a DC level of an unregulated 23V. Since this is derived from a full wave bridge, the period should be 8.3 msec.
DC OK Threshold
The factory setting for the DC OK threshold requires the use of a rather elaborate test circuit; however, it is sufficient in the field to simply back off on R17 to minimum (full CCW) then turn it clockwise until LED CR10 lights. The nominal DC level out at DC OK (P3 pin 1, brown wire) is +3V.
Late serial numbers use a different secondary board with a modified DC OK circuit. On these no adjustment is necessary or provided. The nominal DC level out at DC 0OK (P3 pin 1, brown wire) is +5V.
ADC Range
Push the Master (leftmost) slider up to maximum and pull all the other sliders to minimum. Press LOWER FUNCTION D - 4 and watch the LED in the Master section of the panel (labeled VOLUME /TUNE). Turn R45 clockwise to maximum, then back off counterclockwise until the LED lights. Continue turning CCW 5 degrees beyond this point. Press LOWER FUNCTION to return panel to normal operation.
DAC Null
As stated in the circuit descriptions of Section 3, there must be no DC offset going into the differential input of Z58 if the accuracy of the DAC chip is to be upheld. This input must be within 200uV of 0V. Use a 3-1/2 or 4 digit meter with 100uV resolution MINIMUM! Using an analog meter to measure this is like trying to analyze nanosecond duration pulses in a computer system using a light bulb instead of a fast scope. With your DVM floating in respect to ground, measure between the test points TP1 and TP2 on the main PC board. Adjust R46 until the meter reads to within 100uV of 0V (-0.0001 to +0.0001V). This is a critical adjustment and is quite sensitive. Check your meter with the test leads shorted to be sure it reads 0.0000 prior to making the adjustment.
Lever Position
Measure the DC voltage between the center terminal and ground of each potentiometer in the lever assembly. With the lever at rest (center position), the voltage should read between 2V and 3V. If either is out or range, use a thin 1/2 inch wrench to loosen the nut on the potentiometer. Rotate the potentiometer, keeping the lever centered, until the voltage reads 2.57 and tighten the nut.
The following adjustments are software oriented, using the computer built into the Polaris. No external test equipment is needed.
Tuning
The Polaris has good tuning stability and resolution. Further, it remembers exactly how it was tuned when last shut off; so, when turned on, it does not automatically tune itself. Still, there will be times when it needs tuning; after a change in temperature for example. Press LOWER FUNCTION - TUNE ALL. The Polaris will tune the 6 voices in about 8 seconds. During this process, the tune LED in the Master section of the panel will blink 6 times, provided that each voice is capable or being tuned. If you see that the LED blinks less than 6 times, It is likely a voice cannot be tuned and it will automatically be turned off by the computer. Individual voices may be tuned by pressing UPPER FUNCTION - TUNE ONE. This instructs the computer to tune only the most recently played voice.
The following adjustments can be made only by first going into the adjustment mode. Press LOWER FUNCTION - 1 - (ADJUSTMENTS) to enter the adjustment mode followed by the number for the specific adjustment. The master slider is assigned and used to complete many of the adjustments. After completing the adjustments, press LOWER FUNCTION a second time to return the panel to normal operation.
Volume
Press 1 and move the master slider to adjust the volume of the metronome click for the stop mode of the sequencer. Normally, this will be set to minimum volume by positioning the master slider all the way down.
Press 2 and move the master slider to adjust the volume of the metronome click for the record mode of the sequencer. This usually will be set to maximum.
Press 3 and move the master slider to adjust the volume of the metronome click for the play mode of the sequencer. This usually will be set to minimum.
Press 4 and move the master slider to adjust the volume of the click generated whenever a panel switch is pressed. This usually will be set to minimum.
Press 5 and move the master slider to adjust the volume of the error honk. Normally, this will be set to maximum.
Lever Range
Press 7 and move the levers (the two levers on the left cheekblock, not the sliders) through their entire mechanical range. This will enable the computer to establish the correct lever range provided they were in their center positions prior to pressing switch number 7.
Pedal Range
Press 8 and move the pedal (if pedal option is used) through its entire mechanical range. The computer will establish the correct electrical excursions from this. If pedals are ever changed this adjustment will have to be done with the new pedal.
Volume Offset
The volume offset on each VCA must be trimmed to properly shape the volume envelope. When misadjusted notes may sustain or end abruptly.
Before entering this mode put a scratch program in the main workspace. Use the sequence outlined under "scratch patch" in section 5 of this manual if you need help. You will have to temporarily leave the adjustments mode by pressing LOWER FUNCTION to do this, then re-enter the adjustments mode using LOWER FUNCTION A. Preset the volume by setting the assignable control volume to 1/4 and the master slider volume to maximum. The LED above the master slider must be OFF to be in the volume mode, if on the tune mode is activated.
Press 9 to enter the volume offset mode and move the master slider down to 1/8 on. Play 6 different notes, 1 at a time. After releasing each note move the master slider up until you hear the note bleeding through, then back off carefully on the slider until it just disappears.
Key Sensitivity
Individual keys May be adjusted for touch sensitivity. Before entering this mode select a touch sensitive program by exiting the adjustments mode(LF), then return to the adjustments mode (LF-A).
Press 10 to enter the key sensitivity mode. If one or more keys feels too sensitive, or not sensitive enough, play the key repeatedly and use the master slider to adjust its sensitivity.
Configuration Parameters
The following outline provides the initialized configuration parameters as set on a new unit at the factory. In general, when a Polaris is serviced, these parameters should be set to the initial configuration.
Press B to enter the computer interface configuration mode. Turn on LED'S 1, 2, 3, 7, 8, 9, 10, 11 and 12. Turn off LED'S 4, 5 and 6.
Press C to enter the cassette interface configuration mode. Turn on LED's 1, 2 and 9. Turn off all others.
Press I to enter the sync input configuration mode. turn on LED 2. Turn off LED's 6 and 12.
Press J to enter the sync output configuration mode. Turn on LED's 2 and 7. Turn off LED 6.
Press K to enter the MIDI channel configuration mode. Turn on LED's 1 and 7. Turn off all others.
What To Do If You Lose Your Memory
While it might seem redundant to some, this outline is simply a condensed list of instructions and adjustments already covered in this manual. Its purpose is to provide under one sub-title a concise means for corrective action in the event of having lost everything in memory.
- Press LOWER FUNCTION - D - 12 - STOP.
- Press LOWER FUNCTION - TUNE ALL. Move the master slider to maximum, then back to 1/4.
- Select A-1. You should now have a "scratch sound".
- The LED above the master slider must be off. If on, turn it off to establish the volume mode. The assignable volume LED must be on. Set the assignable slider 1/4 on.
- Press LOWER FUNCTION - A.
- Press 1 and move the master slider down to its minimum position. NOTE: If the master slider is already down to minimum, move it up then set it back down to minimum. The motion of the slider is what causes each adjustment to be set.
- Press 2 and move the master slider up to its maximum position.
- Press 3 and move the master slider down to minimum.
- Press 4 and move the master slider up, then down to minimum.
- Press 5 and move the master slider up to its maximum position.
- Press 7 and move both levers (not sliders) through their entire mechanical ranges.
- Press 8 and move the pedal through its range.
- Press 9 and move the master slider down to 1/8 on. Play 6 different notes, 1 at a time. After releasing each note move the master slider up until you hear the note bleeding through, then back off on the slider until it just disappears.
- Press B. Turn on LED'S 1, 2, 3, 7, 8, 9, 10, 11 and 12. Turn off LED's 4, 5 and 6.
- Press C. Turn on LED'S 2 and 9. Turn off all others.
- Press I. Turn on LED 2. Turn off 6 and 12.
- Press J. Turn on LED's 2 and 7. Turn off 6.
- Press K. Turn on 1 and 7. Turn off others.
- Press LOWER FUNCTION to return Polaris to normal operation.
- LOAD programs and sequences from cassette.
General Operational Checkout
Connect the Polaris to a sound system using the high level output jack. Plug a footswitch into each of the footswitch Jacks and a volume pedal into the pedal jack. Do not initially connect the cassette interface cable or the headphones.
Supply AC power, press LOWER FUNCTION - D - 3 and set the AC input to 117VAC. LED 3 will flash, all other LEDS will turn on.
Press LOWER FUNCTION again to return panel to normal operation. The VOLUME/TDNE LED in the MASTER section should be on; if it is off press the VOLUME/TUNE switch to turn it on. The best signal to noise ratio is obtained when the assignable volume is set high and the master volume is set low.
Select a program, then play up and down the keyboard using single notes and chords. Listen for noises, distortion, loud/soft notes or other anomalies.
Move the levers (on left cheekblock) noting any discontinuity or binding. Test all membrane switches to make sure they work. Using a velocity sensitive program try all keys, making sure none are loud or soft relative to the others.
Play a note, then depress the sustain footswitch and verify that the note stays on after release of the key. Depress the metronome footswitch on and off, tapping it rhythmically with your foot and verify that the LED on the STOP switch flashes in tempo with you. Depress the stop switch to stop the flashing LED.
Reconnect the sound system to the low level output jack and check for distortion or noise. Finally, connect headphones and listen for noise, distortion, clicks, etc.
Testing the Synthesizer Channels
Remove the headphones and reconnect the sound system to the high level output. Load a "scratch program" into the main workspace. Refer to section 5, The Scratch Patch for the correct procedure.
Press LOWER FUNCTION - TUNE ALL. The tune LED in the Master section should flash 6 times indicating that each of the 6 channels have been tuned.
Press LOWER FUNCTION - E to enter the channel check mode. The LEDS in switch numbers 1 through 6 should all be on. If any of these are off, it indicates a faulty channel. The channel circuits are numbered from 1 to 6 starting at the rear of the instrument. To forcibly enable a disabled channel, or disable an enabled channel, press the corresponding number switch. Press LOWER FUNCTION again to return the control panel to normal operation.
Press the SAWS/PULSE switch in the two oscillator sections so that their LEDs are on. Then play six different notes, one at a time. When you press each note you should hear nothing. This is because the pulse waveshape has been selected, yet the pulse width is zero in a scratch program. For each note verify that pressing the SAWS/PULSE switch in oscillator 1 causes a note to be heard. Play six different notes again, this time verify that pressing the noise switch for each note causes noise to be heard. This exercises the waveshape and noise bits in all six channels.
Move the PULSE WIDTH sliders in the two oscillators to their center positions. Play six different notes, one at a time. When you press each note you should hear the oscillators. For each note verify that pressing the RING MOD switch causes the pitch to jump an octave. This exercises the ring modulation bit in all six channels.
Press the DETUNE switch in the assignable control section and move the assignable slider all the way up. Play six different notes, one at a time. When you press each note you should hear two pitches a semitone apart. For each note verify that pressing the SYNC switch causes only one pitch to be heard. This exercises the sync bit in all six channels. When finished move the assignable slider to the center position to bring the oscillators back in tune.
Move the CUTOFF slider to about 3/4. Play six different notes, one at a time. When you press each note move the RESONANCE slider up and down slowly. You should hear seven steps along its range. In the highest position of the RESONANCE slider the filter should self-oscillate. You may want to use the CUTOFF slider to retune the filter to a setting that makes the resonance steps easier to hear. It is also easier to hear if you turn off one of the oscillators by setting its pulse width to zero. Check the seven filter tuning steps for all six notes. This test exercises the three resonance control bits in all six channels.
Reload a "scratch program" into the main workspace. Press LOWER FUNCTION - TUNE ALL to make sure the oscillators are in tune. Press the VOLUME/TUNE switch so that its LED is on; the MASTER slider will now function as a master tune slider. Play one note, such as middle C, and listen carefully to the beat frequency between the two oscillators. It should be slower than 0.5Hz. If it is too slow to hear select DETUNE and adjust the assignable slider so that you can hear the beat frequency. Slowly move the master slider while listening to the beat frequency. If the beat frequency changes noticeably from point to point on the slider it indicates that the DAC is misadjusted or that not all the bits in the DCC circuit are working properly. If the beat frequency remains the same as you move the slider, the DAC is tracking correctly. This test checks DAC tracking and offset. Center the master slider to return tuning to "A-440" Press the VOLUME/TUNE switch to exit the tune mode and restore the volume mode.
Checking for Proper Adjustments
Note: The switch sequences or comments after each paragraph (in bold print) refer to the adjustment being tested. That adjustment should be performed if the test fails. The adjustment procedures are detailed earlier in this section.
Select the BEND LEVER RANGE switch from the assignable control section and move the assignable slider all the way up (away from you). Play a note and move the pitch bend lever slowly toward you. The pitch should begin to change as soon as you begin to move the lever and should continue to change until the lever has reached its maximum travel.
(LOWER FUNCTION - A - T)
Without touching the bend lever move the assignable control up and down. Verify that the pitch does not change.
(Lever pot wiper, 2.5VDC at rest)
Select the MOD LEVER RANGE switch from the assignable control section and move the assignable slider all the way up. Move the sweep rate slider to about 2/3 of its travel. Play a note and move the mod lever slowly toward you. Vibrato should begin as soon as you begin to move the lever and should continue to increase in depth until the lever has reached its maximum travel.
(LOWER FUNCTION - A - T)
Without touching the modulation lever move the assignable control up and down. Verify that the modulation does not change.
(Lever pot wiper, 2.5VDC at rest)
Select the PITCH PEDAL switch from the assignable section and move the assignable slider all the way up. Starting with the pedal in the "heel" position play a note and slowly move the pedal to the "toe" position. The pitch should begin to change as soon as you begin to move the pedal and should continue to change until the pedal has reached its maximum travel.
(LOWER FUNCTION - A - 8)
Move the Release sliders in both envelope sections to about mid position. Play six different notes, one at a time. After releasing each note the note should die evenly and about the same time as the note before it.
(LOWER FUNCTION - A - 9)
Push all of the sliders on the control panel all the way down. Press LOWER FUNCTION - D - 4 and make sure the LED in the master section lights when the master slider is moved all the way up. Lower the master slider (slightly) and the LED should go out. It should take no more than 10% of the slider travel to turn off the LED.
(LOWER FUNCTION - D - 4 and R46)
Move the master slider all the way up, press LOWER FUNCTION, reselect the scratch sound, then move the master slider to mid position to restore normal operation to the panel.
Press the STOP switch and verify that the LED is flashing but you do not hear the metronome.
(LOWER FUNCTION - A - 1)
Select an empty sequence slot by pressing UPPER FUNCTION - SELECT SEQUENCE - 1-12 (one that is not lit). Press the record switch and verify that you can hear the metronome while the LED is flashing. Record a small sequence then press the STOP (or PLAY) switch.
(LOWER FUNCTION - A - 2)
Press PLAY, then the metronome footswitch and verify that you cannot hear the metronome while the sequencer is playing. Press STOP.
(LOWER FUNCTION - A - 3)
Select an empty sequence slot (as above), then press PLAY and verify that the error honk is present.
(LOWER FUNCTION - A - 5)
Make sure that you hear no clicks or pops when the sweep SINE/SQUARE switch is pressed.
(LOWER FUNCTION - A - 4)
Press LOWER FUNCTION and enter each configuration mode below (B - C- I - J - K). In each mode verify that the LED'S are in their specified state (on or off). Correct them as necessary by turning them on or off:
Press B (computer interface). LED'S 1, 2, 3, 7, 8, 9, 10, 11 and 12 should be on. LEDS 4, 5 and 6 should be off.
Press C (cassette interface). LED'S 1, 2 and 9 on. All others off.
Press (sync input). LED 2 on. LED'S 6 and 12 off.
Press J (sync output). LED'S 2 and 7 on. LED 6 off.
Press K (MIDI channel). LED'S 1 and 7 on. All others off.
Press LOWER FUNCTION to return panel to normal operation.
Testing the Interfaces
The Polaris under test (P-U-T) should be connected to a known working Polaris (K-W-P) for checkout of the interfaces. Connect the sync out of the P-U-T to the sync in of the K-W-P and the sync out of the K-W-P to the sync in of the P-U-T. Connect the MIDI ports the same way (out to in). Connect the Chroma interface port of the P-U-T directly to the Chroma interface port of the K-W-P. Connect the K-W-P to a sound system using the high level output jack and supply it with AC power. The P-U-T should already be connected to a sound system and have power. Both units should be turned on.
On the P-U-T press LOWER FUNCTION - B, then turn on 4 and turn off 10. Playing on the keyboard should cause both units to sound. When this has been verified (it is easier if they are out of tune with each other) press 4 again to disable the Chroma interface. Verify that the P-U-T plays only itself. Turn on 10 and both units should sound. Press 10, 12, LOWER FUNCTION to return the panel to normal operation.
On the K-W-P press LOWER FUNCTION - B, then turn on 4 and turn off 10. Make sure the K-W-P plays both units. Turn off 4 and make sure the K-W-P plays only itself. Turn on 10. Make sure the K-W-P plays both. Press 10, LOWER FUNCTION to return the panel to normal.
If the STOP LED is not flashing on either unit press the STOP switch to make it flash. Press LOWER FUNCTION - H - 2 on the P-U-T and LOWER FUNCTION - H - 5 on the K-W-P to tell the P-U-T to generate a sync and the K-W-T to follow it. Press LOWER FUNCTION on the P-U-T to restore operation to the panel.
Verify that the P-U-T is controlling the K-W-P by repeatedly pressing STOP on the P-U-T. The flashing LED should stop and start on both units. When this has been verified leave the LED'S so they flash, then press LOWER FUNCTION - H - 5 on the P-U-T and 2 on the K-W-P. Press LOWER FUNCTION on the K-W-P to restore its panel to normal operation. Make sure that the K-W-P can start and stop the P-U-T in the same manner. Leave the LED's flashing. Press LOWER FUNCTION - H - 1, LOWER FUNCTION - STOP on the K-W-P, then press 1, LOWER FUNCTION - STOP on the P-U-T to restore the panel to normal operation.
The cassette interface tests require the use of a Factory Programmed Polaris data cassette tape, a cassette recorder/player and a cassette interface cable. We recommend the Radio Shack model CCR - 81 cassette recorder/player. Cassette interface cables are available from Fender (part number 30-2204901) or you may use one from Radio Shack (catalog number 26-1207).
Remove the sync in cable and install the cassette interface cable. The gray sub-miniature plug connects to the remote jack, the gray miniature plug to them microphone input jack, and the black miniature plug to the earphone output jack on the recorder.
Insert the data cassette into the cassette player. Press UPPER FUNCTION - LOAD ALL. Press PLAY on the cassette player. This will load all the programs. When the tape stops and the UPPER FUNCTION LED goes out, press UPPER FUNCTION - LOAD ALL again to load the demonstration sequences.
Simultaneously press the PAUSE, PLAY, and RECORD switches on the cassette recorder/player. While watching the record LED on the cassette recorder, press UPPER FUNCTION - SAVE ALL PROG. When the data is transmitted, the LED on the cassette recorder should light. Terminate the save operation by pressing UPPER FUNCTION. On the cassette recorder press STOP, then release the PAUSE.