Guitar Synthesizer Repair Tips

Erratic or Unreliable GR-700

What seems to be the problem?

    Perhaps one day one string on your GR-700 suddenly stops working. Or you can hear the string, but it plays very softly, followed by intermittent bursts of noise. Or you turn the GR-700 on, and after a few minutes, it starts making loud noises. Here is an audio example of one kind of GR-700 failure.

    You most likely have a failed 80017a VCF/VCA chip. Here is a list of typical 80071a symptoms:

    • Erratic or sudden loud noise from synthesizer output, particularly after 10 minutes of powering up.
    • Note hang-ups or long sustain.
    • One synth voice will not respond to filter or amplifier changes.
    • Unstable operation.
    • One particular voice or string will not sound, "D" string, "A" string etc.


    If you are familiar with the eighties Roland synthesizers, then you have likely heard about the dreaded 80017a VCF/VCA chip failure issue. Many synthesizers built by Roland in this period used the 80017a chip: the Juno 106, MKS-30, HS-60 and of course the GR-700. The 80017a is basically a voltage-controlled filter and a voltage-controller amplifier on a single, customized chip made for Roland. The actual components in the 80017a were found as individual elements in the earlier Juno 60 synthesizer: an IR3109 and two BA662 chips. The IR3109 was also used as the heart of the excellent -24 dB low-pass filter in the Roland GR-300.

    Why exactly Roland chose to consolidate those three chips (and some surface mounted resistors and capacitors) onto a single ceramic chip dipped in plastic remains a mystery. Arp did something similar with its 4034 filter module, perhaps to (unsuccessfully) dodge a lawsuit from Moog. In any case, early in the process there were failures with the chips, and Roland issued a service bulletin and replaced lots of chips. Then, as the chips aged, problems started to show up with again. Third party suppliers started making clones of the original chips using modern equivalents. And I sold quite a few working chips on ebay after gutting GR-700s for parts. I extensively tested these chips, and no one had a subsequent failure from the chips I pulled. But this bothered me: would it be possible to modify a GR-700 in some way that would guarantee against a future 80017a chip failure?

    As it turns out, the answer is to remove the problematic resin coating around the components. And this was not my idea, someone sent me a link to a YouTube clip showing how to get the job done. I happened to be working on a GR-700 that needed five (!) 80017a chips. I had five failed chips on hand, and used the Acetone procedure to remove the resin. Each chip was then individually tested in a special socket, running continuously for 12 hours with no failure. As each chip passed the test, I labeled it and replaced it in the GR-700.

    The result is flawless operation. I do not know why the resin causes problems, but I am guessing that with aging the resin builds up electronic capacitance, causing the chip to fail once the temperature in the synthesizer warms up. This is the best possible solution to the 80017a problem. You keep the original chips that Roland designed, maintaining the sound of the instrument, and you protect against future failures as well.
Failed 80017a chip from lot number 42B, with resin in place.
Resin shell removed from the chip by soaking in Acetone.
Tested and relabeled chip, ready for installation in the GR-700.
The custom Roland IR3109 chip shown in the GR-300. This chip is part of the 80017a assembly.
Click on any image to enlarge in new window.


If one string does not sound, make certain that it is not your 24-pin cable!

An easy way to determine if you cable is working correctly on the GR-700 is to press the EDIT foot pedal, followed by 4 and 8. This puts the GR-700 in tuning mode. Play each string on the GR-700, and you should see the display change for each string. The displays shows "1" for the high E string, "2" for the B string, down to "6" for the low E string. If the GR-700 responds to all six strings, then your cable is good, and most likely you have a failed 80017a chip.

Channel and String Identification

It is very important to correctly identify the failed 80017a chip. The chart below shows how the guitar strings map to the channels inside the GR-700:

  • Channel 1 = High E string.
  • Channel 2 = B string.
  • Channel 3 = G string.
  • Channel 4 = D string.
  • Channel 5 = A string.
  • Channel 6 = Low E string.
80017a in Roland Schematics:

Detail from Juno-106 Service Manual.
Detail from GR-700 Service Manual.
80017a block diagram from Juno-106 Service Manual
Additional Resources for the Juno-106/80017a Repair:

Below are links to download a Juno-106 service manual, to download a pdf file from Roland on the 80017a failure, and a MKS-30 main schematic.



Juno-106 Service Manual.
Roland Service Note
MKS-30 Schematic
Juno-106 Failed Chip Test Procedure.
Juno-106 Calibration
GR-700 Calibration


Above are various technical documents to help with your repair. I have added documents here on calibration. When the 80017a chip is replaced, the small trimmers around the chip may have to be adjusted. These trimmers adjust the level, DC balance, resonance and filter cutoff for each chip. Level controls how loud each chip is, Resonance fine tunes the amount of feedback resonance, Filter Cutoff is a fine tune control for the low-pass filter cutoff. Finally DC Offset adjusts the start and ending output of the chip so that when the sound stops, the amount of voltage is zero.

The synth will work without making these fine adjustments, but you may find one voice louder than another, or you may hear soft clicks as a sound decays, indicating some DC offset. While the technical documentation provides specific procedures for setting each chip, most experienced technicians rely on their ears for the final judgment. Also, Roland tends to be cautious with their recommended settings, so users may use these adjustment options to expand the tonal range of their synth.
Locating Specific Chip Failure:

MKS-30 lnterior Photo. Summing resistors circled in rear.
Detail from GR-700 Interior. Resistors in rear.
Summing Resistors Close-up, GR-700. Test side is on left.


There are six summing resistors used to combine each voice in these synthesizers. In the Roland GR-700 and MKS-30 example, shown above, the resistors bridge across the voice section to the output section.

If you are not sure which voice is causing a problem, you can use a scope to see the VCF/VCA output by touching the left side of each resistor. If you do not have a scope, then attach a wire to chassis ground, and then touch the wire to the left side of each resistor. This will mute the output of the synthesizer voice. When you mute the output of the bad VCF/VCA, the erratic sound should stop.
Video Clip of Removing 80017a Chip from Printed Circuit Board:

Roland 80017a Chip Removal from Printed Circuit Board, GR-700
This video shows the removal of a 80017a chip from a GR-700 printed circuit board. The tools I used were a Radio Shack 30 watt soldering iron, desoldering wick, soldering helper, and Caig DeoxIT D5. The basic Radio Shack 30 watt soldering kit has almost everything your need. I find that spraying the Caig DeoxIT D5 between operations helps keep the PCB clean, and helps the old solder flux move on to the desoldering wick. After I have removed the solder from the pins, I used the soldering helper to line the pins up, then gently rock the chip back and forth to make sure everything is loose. Rather than pull the chip out, I first push on the pins on the soldering side, then gently tug at the chip. It comes right out. If you have not tried this before, I recommend practicing on some spare parts, as this can be tricky and frustrating.
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