Guitar Synthesizer Repair Tips

Vintage Hex Guitar Synth Pickup Repair

What seems to be the problem?

You have damaged the ribbon connector that leads from the hex pickup to the Roland circuit board. These ribbons become very brittle as they age. If you remove the electronics for repair, it is quite possible to crack the ribbon ever so slightly. The metal traces are attached to a plastic ribbon, and are very breakable. Fortunately, there is a fix for this problem, but be forewarned, this is the most difficult and tedious vintage Roland repair.

Before you start this repair, it is important to check that the ribbon is the problem. Remove the ribbon connector from the circuit board, and using a multi-meter, check the impedance between contacts. You should read either approximately 80 or 160 ohms for a "narrow" pickup, or 800 to 1.6K ohms for a "wide" pickup. There is more information about these pickups on the guitar electronics page.

Since there is no way to repair the ribbon connector itself, you will cut the ribbon connector off the hex pickup, remove the potting wax around the pole pieces, and then solder replacement wires to a new ribbon connector. I have successfully repaired a half dozen pickups this way. It can be done with patience and the right tools. Allow and hour or two for the whole procedure.

Parts and Tools, etc.:
  • Dremel Tool with basic attachments.
  • Low wattage soldering iron and solder.
  • Replacement Roland 12-position Ribbon Cable.
  • Masking tape.
Where to find the Roland ribbon? You can send me an email. I have a lot of parts from my various Roland repairs. Often I can recover a ribbon connector, and if it is in great condition, I will sell the part on ebay. But I have a few that are not perfect for 24-pin operation, but which will work fine for this repair.
Re-Wiring Original Hex Pickup:

Hex pickup ready for surgery. The ribbon connector has been removed, and tape is placed around the pickup to protect the casing. Enough potting wax has been removed to allow soldering access to the pole pieces You only need to expose seven poles. New wires attached to the hex pickup. The top pin is green (common) and the lower row is high E to low E (left to right).
Close-up detail of wires attached to the pole pieces in the hex pickup. The bottom green wire is the common lead shared by all the elements. The pickup with replacement wires attached, soldered to a spare Roland 24-pin ribbon cable. The original ribbon connector is also in the picture. These are the Dremel attachments I used. The last repair totally destroyed three of my brushes, as the epoxy was very, very hard.


The above photos show the conversion of a "narrow" older-style hex pickup. A Dremel tool was used to remove the epoxy-type potting wax around the pole pieces of the hex pickup. When removing the epoxy-type potting wax, you only want to remove just enough to solder on to the pole pieces. Removing too much will permanently damage the pickup. Also, the Dremel brush can damage the casing of the pickup, so to be on the safe side I taped up the edges of the pickup to prevent damage. I would work a little bit, then closely inspect the pole pieces. When I felt I was close enough, I used a multi-meter to test for conductivity, in a "narrow" pickup, you should read around 80 ohms between the element and the common, or ground. With a "wide" pickup, you should read about 800 ohms.

You will note that one row of six pins are common, or ground. You only need to uncover one of the common pins for this repair. Refer to the photos below to orient your epoxy removal to access the six lead pins and one common pin.

When I was finished with the Dremel tool, I cleaned everything up and carefully soldered seven wires to the pickup, one for ground (the common for all six elements), and one wire for each element. Then everything was tested again. The resistance between two elements (not between the element and ground) should read 160 ohms for the "narrow" pickup, and 1.6K ohms for the "wide" pickup. I have tried different Dremel brushes for this work. The video clip below shows a repair using a nylon brush.

WARNING:

The last repair I did had particularly difficult epoxy. The repair destroyed three of my Dremel brushes, and as the metal brush disintegrated, tiny metal wires went into my face. GR user Peter Kulich reported a similar experience to me, but then he is Canadian. Anyway, when I was done, it was up to my wife pulled these tiny wires out with tweezers. Fortunately, I was wearing eye protection and a breather which covered most of my skin, but it was an important reminder to protection at all times.

This is a "wide" hex pickup with new wires attached. The top row of pins are all ground, or common.
This is a "narrow" hex pickup with new wires attached. The top row of pins are all ground, or common.


Repaired pickup installed:

This is a photo of a wide pickup set to be installed in a Pedulla XJ-S with Roland electronics. In this installation, the ribbon connector was cut down to seven traces. This ribbon will be used with the remaining ribbon part. New wires attached to the hex pickup ribbon. Refer to the G-303/G-808 schematic for the wiring order.
Close-up detail both ribbon parts inserted into the ribbon connector on the circuit board. Distant view with wire leads shown as well. In the Pedulla XJ-S the electronics are in a very narrow cavity, with barely enough room. Here is the entire assembly in the guitar, with black masking tape added around the connectors to prevent shorting.


Video Clips of Repair and Testing:

Using a Dremel Tool with the Hex Pickup
Brief video clip of using a Dremel tool to remove enough epoxy-type potting wax from a "narrow" hex pickup to solder new wires to the pole pieces.
Final Testing of Pickup
Brief video clip of testing a repaired pickup for GR user Nils. Only the pickup was installed for this test.


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