CA Guitar Repair Blog: Ibanez RG350DX Rehab

Electronics Overview

The Ibanez RG350DX features a middle single-coil pickup flanked by neck and bridge humbuckers; all three being ceramic. The pickups are wired to a five-way selector switch, master volume and tone pots; and a mono output jack [Fig. 1]. The underside of the pickguard is partially shielded with aluminum foil, while the pickup and control cavities are shielded with conductive shielding paint [Fig. 2].

Fig. 1: Pickguard-Mounted Electronics

Fig. 2: Shielded Pickup and Control Cavities

About the Pickups

The neck humbucker is an Infinity 3 [INF3], the middle single-coil an Infinity Single 3 [INFS3], and the bridge humbucker an Infinity 4 [INF4]. Both humbuckers feature 12 adjustable hex head pole screws in lieu of slotted threaded pole pieces, while the INFS3 has six similar pole screws. Unfortunately, the hex head pole screws of all three pickups are grimy, cruddy and corroded [Fig. 3].

Fig. 3: Corroded Hex Head Pole Screws

The INF3 features a red-jacketed coaxial cable containing white [hot] and red [series link] leads, and a braided shield [ground]. The INF4 employs a similar cable, albeit with a grey jacket. The INFS3, however, is wired into the circuit via white [hot] and black [ground] leads, both unshielded [Fig. 4].

Fig. 4: Pickup Cables/Leads

Selector Switch Malfunction

As received, there's something odd about the way the pickup selector switch functions [Fig. 5]. In Position 1 [INF3 only], only the INF3's inner coil is active, when it should be operating in full humbucker mode [both coils active]. The same thing happens when Position 5 [INF4 only] is selected. In positions 2, 3 and 4, however, the switch works as it should.

Fig. 5: Selector Switch Malfunction

The Root of the Problem

So, is the switch faulty? No, because I've checked it thoroughly and it functions normally. The root of the problem has been traced to desoldered switch tabs and the back of the volume pot. In Fig. 6 below, I've circled the areas in question for your convenience.

Fig. 6: Wiring Problems Identified

Let's examine the switch tabs now [Fig. 7]. From left to right are the three white [hot] leads for the INF4, INFS3 and INF3, the red lead carrying the switch output to the volume pot; and a black ground wire that is active in positions 2 and 4. These are where they should be, so we'll leave them alone for now. Right then, see those two numbered desoldered tabs? Tab "1" is where the series link [red lead] for the neck humbucker [INF3] needs to be connected to. Meanwhile, tab "2" is where the series link [red lead] for the bridge humbucker [INF4] should be soldered to. But, since these two series link leads are missing, where have they been soldered to instead?

Fig. 7: Desoldered Switch Tabs

Folks, here's where the "missing" series link leads are, arrowed for your convenience [Fig. 8]. Wonder of wonders, they've been soldered to the back of the volume pot! What this means is that the outer coils of both the INF3 and INF4 have been grounded permanently. Now, we know why both humbuckers can only function as single-coils.

Fig. 8: Grounded Series Link Leads

Yet another startling discovery is that the braided shields of both the INF3 and INF4 have been disconnected from the circuit, snipped short and taped off. Why anyone would want to do this is beyond me, but it is what it is. In any case, Fig. 9 below is a graphical representation of the faulty switch/volume pot wiring scheme I need to correct.

Fig. 9: Faulty Switch/Volume Pot Wiring Scheme

Normal Operation Restored

What a relief! I've managed to rewire the five-way selector to original specs [Fig. 10]. The series link leads have been resoldered to their switch tabs, and braided shields grounded to the back of the volume pot. Fig. 11 below is a graphical representation of the corrected switch/volume pot wiring scheme.

Fig. 10: Switch Rewired to Original Specs

Fig. 11: Corrected Switch/Volume Pot Wiring Scheme

Exhaustive testing of the corrected wiring scheme has revealed that in positions 1 and 5, both coils of the INF3 and INF4 are active, enabling them to operate in full humbucker mode [Fig. 12]. Last but not least, if you'd like to watch yours truly putting the rewired switch through its paces, there's a YouTube video right at the bottom of this page.