Ibanez RGA32 : broken active pickups ?

Pickups, wiring schemes, switch techniques and onboard active electronics for guitars

Ibanez RGA32 : broken active pickups ?

Postby JiM » 28 May 2012, 20:19

Hi folks,
My bandmate recently bought a guitar second-hand, an Ibanez RGA32, with a beautiful natural mahogany finish and active Ibanez LZ3 pickups.
The problem is the sound of it : it sounds like a starved fuzz, if at all ! :(

It happened right after the replacement of the batteries (2 x 1.5V AA), and at some point he was receiving radio as well !
The sound is actually very weak, and when you attack the strings harder a loud, badly gated fuzz tone appears.

I did not find the exact schematic, but it's like the RGA42 without the EQ board and with a normal tone control :
http://img697.imageshack.us/img697/4842/rga42rga42fm.jpg
or like an ART300 with a single volume and a 3-way blade switch :
http://circuitwiringdiagram.com/wp-content/uploads/2010/02/ibanez-guitar-wiring-diagram.png
The preamps are inside the pickups, and totally enclosed in epoxy :
http://imageshack.us/photo/my-images/714/lz3k.jpg/

According to the RGA42 diagram, it seems that the white wires from the pickups carry -3V supply voltage.
I suppose this comes from an voltage inverter/charge pump inside the pickups, and the preamp is actually working with 6V rail-to-rail.
With 3.23V at the batteries (fresh alkalines), i measure about 1.1V at these white wires. When the strings are hit hard enough, and fuzz is heard, it jumps at about 1.3V.
I tried separating the white wires, that changes nothing. I tried lowering the voltage (just one AA battery), it just halves the voltage at the white wires and set the fuzz

I suppose that the charge pumps are fried, maybe because of some over-voltage or wrong polarity (that would be a shame for Ibanez to forget adding protection diodes ...)
The preamps would then be under-powered and/or badly biased, and give a badly distorted and gated sound.
Does this diagnostic seem correct ?

Then, what should i do ?
  • Redo the whole wiring, just in case ?
  • Try and degoop these things and fix the charge pump (if that's really the problem) ?
  • Increase the supply voltage to 6V or even 9V to get some headroom back (hoping this will not destroy the preamps further) ?
  • Add an external charge pump (or more batteries) to supply -3V into the white wires (hoping this will not destroy the preamps further) ?
  • Ditch the pickups and tell him to buy EMGs ?
I can post pictures or sound samples if this may help.
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Re: Ibanez RGA32 : broken active pickups ?

Postby DrNomis » 31 May 2012, 05:36

Sounds like it could very well be the pickups and they may need replacing, I've heard lots of good things about EMG pickups.... :thumbsup

Personally I wouldn't bother trying to de-goop the original pickups because the epoxy is very hard, it'd be easier to just replace the pickups, one thing, have you checked to make sure the battery is a fresh one?.... :hmmm:
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.
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Re: Ibanez RGA32 : broken active pickups ?

Postby JiM » 31 May 2012, 15:22

The guitar now works fine, for no apparent reason ! :slap:
I was playing it for a while, in all its sputtery fizziness, when i noticed some rythmic clicks. Like a starved charge pump desperately trying to oscillate. And suddently, it stopped. And i had a nice, clean tone.

I suppose that the batteries were too fresh, providing more than the expected 3V (about 3.25V). Playing for a while would have discharged the batteries just enough for proper operation. The white wires now provide a proper -3V.
I was unable to reproduce that with a regulated power supply though, the pickups worked fine from 4V down to 2V, where rythmic clicks starts.

Or it is a bad contact somewhere, that somehow went better. In that case, it's a ticking bomb waiting for the next gig.

For now, i've just put it back together, with a tight wrap around the wiring to keep it in place. I'll test it at tomorrow's rehearsal.
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Re: Ibanez RGA32 : broken active pickups ?

Postby DrNomis » 31 May 2012, 16:46

It may have even been a dry solder-joint somewhere that was the cause of the problem... :hmmm:
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