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More about the Pickups

Checking the Impedance

Vintage Roland and Ibanez Electronics In Depth:

Version History "Wide" (12 mm) and "Narrow" (10 mm) Pickups

Narrow Pickup
10 mm "narrow" 80 ohm pickup on the left next to 12 mm "wide" 900 ohm pickup installed in a late model G-808.
Narrow Pickup in G-303
"Narrow" pickup installed in a G-303. This is one of the earlier models, and has the high-gain circuit.
Wide Pickup
"Wide" pickup installed in a G-303. This is one of the later models, and has the low-gain circuit.

After years of working with Roland vintage electronics, I finally noticed that there were two variations on the familiar hex pickup. One pickup is small, with an impedance of 80 ohms, and the other pickup is slightly larger, with an impedance of around 900 ohms. For my purposes, I labeled these pickups as "wide" or "narrow." One pickup is around 10 mm wide, and the other is about 12 mm wide. Generally, the narrow pickup seems more common in earlier guitars, and the wider pickup is common with the later models.

I had been exchanging emails with GR-user Jonathan Prince, who had, once upon a time, ordered a replacement hex pickup from Roland. He mentioned he had misplaced the paper they sent with the pickup explaining what parts to replace when he installed the new pickup. I emailed back that his memory was probably fooling him, as there was no official Roland documentation on the pickup change. And then...low and behold...Jonathan sent me this memo from Roland! Dated July 6, 1995, from a Mr. Mark Wire, it lays out all the technical information on the pickups that I had only surmised! View the original note from Roland sent to Jonathan Prince.

"We don’t have any humbucking pickups for your G-808 (I physically went out to parts dept. to check.)" begins the note! Well, that is some bad news! But Mark Wire was able to find a replacement hex divided pickup! And Mark notes the serial numbers of the new and old pickups: Old type: #601 Pick-Up 22380601 New type: #610 Pick-Up 22380610.

Mark lists the serial numbers of guitars that use the older style, #601 (or part number 22380601) divided pickups:

G-202 before serial no. 411600
G-303 before serial no. 413100
G-505 before serial no. 412600
G-808 before serial no. 413100

Mark goes on to outline the resistors that need to be changed for the new #610 pickup. As it turns out, these are exactly the modifications that I outline in the notes below. For the G-303, G-505 and G-808, each string needs two resistors changed, one effecting the synthesizer signal, and the other effecting the hex fuzz signal. The G-202 has a different hex fuzz circuit, so only six resistors need to be changed.

I also have to add this: I picked up some G-707 electronics pulled from a guitar some years ago, and I did find a G-707 circuit board wired to support the older, narrow pickup. In the case of the G-707 guitar, you need to check to following resistors: R23, R26, R29, R35 and R38. According to the schematic, these resistors should be 10K, but in this rare G-707 circuit board, the resistors were only 1K. This 10:1 ratio difference is in keeping with all the other changes.

When switching from the 80 ohm (narrow) to 900 ohm (wide) pickup, there is a 10:1 increase in impedance, likewise, it is necessary to change the negative feedback loop resistor by a similar 1:10 ratio, from 330K to 33K, and from 1 M to 100K.

Mark also mentions that the pick guard must be slightly enlarged to accommodate the wider pickup, but only on the G-202 and G-505, the only guitars with pickguards. Also, while I measured these pickups as 10 mm and 11 mm respectively, Roland has them listed as 10 mm and 12 mm in size.

One more thing that I must mention: apparently Mark Wire did not have any official Roland stationary when he penned this missive to Jonathan. So, and I think this is the coolest part of this whole note, he apparently decided to trace out the official Roland Company logo at the top of the note. I mean, nothing says official Roland service notice like a hand drawn Roland logo! I have never met Mr. Mark Wire, but I sure like his dedication to customer satisfaction! Not only did he personally check the parts department to see if he could find a G-808 pickup, but he took the time to add the Roland logo to this note! Excellent!

Roland High Gain Pickup Roland Low Gain Pickup
High Gain Circuit: the yellow arrow points to a 330K resistor in the negative feedback loop of the G-303/808/LPK-1 board. Low Gain Circuit: the yellow arrow points to a 33K resistor in the negative feedback loop of a different G-303/808/LPK-1 board.

"Narrow" (10 mm) Pickup - Uses High Gain Circuit
"Wide" (12 mm) Pickup - Uses Low Gain Circuit

You need to actually check your own card with a multi-meter, or read the resistor values to see what you have. I worked on a LPK-1 card which had the 330:1 gain structure for the "narrow" pickup, rather than the 33:1 design shown in the LPK-1 schematic.

When I installed the correct "wide" pickup for the 33:1 circuit, the LPK-1 would work with the GR-300, but the internal trimmers were very sensitive. After a quarter-turn, the gain would be too high for any kind of dynamic control. The solution was to replace the 330K resistors with 33K resistors. After this change, everything worked perfectly. I also checked the gain settings with the more sensitive GM-70, because the ladder LED display gives a much more accurate reading than one red LED on a GR-300.

Primary Resistors Hex Fuzz Resistors
Primary Resistors: Click image to enlarge
Hex Fuzz Resistors: Click image to enlarge

The yellow arrows in the first picture on the left point to replacement resistors R12, R22, R32, R42, R52 and R62 in a LPK-1 board. The original brown 330K (5% tolerance) resistors were replaced with blue 33K (1% tolerance) resistors. These resistors set the gain for the synth signals.

The yellow arrows in the second picture point to replacement resistors R14, R24, R34, R44, R54 and R64 in a LPK-1 board. The original brown 1M (5% tolerance) resistors were replaced with blue 100K (1% tolerance) resistors. These resistors set the gain for the hexaphonic fuzz circuit.

Checking the Impedance of the Divided Vintage GR Synth Pickup

A vintage Roland GR pickup consists of the divided pickup plus an attached ribbon cable. Be careful when working with these pickups, as the ribbon cable will become brittle with age and is easily damaged. There are 12 contact points on the ribbon cable. The first seven are for the hex pickup, and they include a common or ground point, plus the six string outputs. Reading from the long edge of the ribbon to the solder points, the outputs are strings #4, #3, #1, #2, ground (common), #5 and #6.

The next five contact points are actually for attaching wires to the top panel guitar electronics. Reading in the same direction, they are the p-touch, p-touch lock, the guitar pickup output, ground, and the normal guitar out. Refer to the diagram below from the Service Manual Schematics.

gr pickup details gr pickup details gr pickup details
L-R, strings 4, 3, 1, 2, ground, 5, 6, p-touch, p-lock, guitar pickup, ground and normal output. Using a multimeter to test string #3 for resistance. A working element should read 78 to 80 ohms. Diagram from the Roland Service Manual Schematics showing the wiring of the ribbon connector.

To test each element in your pickup, attach the ground lead from a multimeter to the ground (common) contact point for the hex pickup, then move the positive test lead to the various pickup outputs. Depending on whether you have a wide or narrow pickup (see above), a working pickup element should read 80 to 90 ohms for the narrow version, or 800 to 900 ohms for the wide version. If you read between two pickup output points, you should see 160 ohms or 1.6K (depending on the version of pickup). This is double the reading of an individual pickup. If you get a reading of 0 ohms, or an open circuit reading (infinite resistance), then you likely have a damaged pickup.