curtisa

Two alternatives. 1. Using an added relay to provide an extra set of contacts: Advantages - makes use of the existing switch you've already installed. Disadvantages - more bits to buy; as the battery dies you'll lose the ability to do the 'plus bridge' pickup selection. Note: Relay and diode shown above can be bought from Amazon (eg here and here), but loads of other places sell them. 2. Using a different switch: Advantages - pickup selection will still work if the battery goes weak. Disadvantages - this style of switch seems to be hard to come by and is a lot more expensive. May not be available in the same size as the one you already installed. The switch shown is specifically this one. It's larger than the one you already bought so it would be wise to check it will still fit and will look OK if you're considering going this route. LED colour is red, but it's also available in blue, green, yellow and white.

You can't. At least, not without adding extra circuitry that expands the number of switching contacts to your existing switch (hence my earlier suggestion of adding a relay) or using a different switch that already includes more contacts.

No. You're still proposing sharing the circuits, which is half your problem.

You could install a little relay inside the control cavity to be driven from the switch. The contacts on the relay would then drive the LED and pickup selection separately and correctly. But it's a lot of fiddling around.

Yep - it will never work, sorry. The battery is dead-shorted in the off position, which is why it's getting hot and dying quickly. You're also sharing the LED circuit with the pickup. There's only one switching contact inside the pushbutton, and you really need two independent contacts - one for the LED and one for the pickup selection. You could make the switch work but only if you dispense with the LED.

No, it'll be something else. Pickup DC resistance will be in the order of many K-ohms, which would result in insufficient current to cause battery heating. It's more likely to be a dead short. The photos will probably show more clues.

How exactly have you got the switch wired? If it's anything like the below switch I don't think this can be done without additional circuitry and components, or a different pushbutton; The LED needs to be switched on and off using the contact in the switch, but you also need a dedicated contact for the pickup on/off function - they cannot be shared. Something's funky with the wiring. The battery getting hot suggests it's being shorted out when the switch/LED is in the off position. Post up some detailed shots of the wiring for the switch and battery.

Correct. Harmonic placement is irrelevant, as the position of any harmonic is never constant due to the way the instrument is played. If you took a 24 fret guitar and had your neck pickup somewhere around the implied 26th fret position, it wouldn't automatically sound warmer if you fretted at the 2nd fret, thereby realigning the string vibrations/pickup position with the 2nd harmonic. If your sonic (and visual?) preference is for the neck pickup to be as close to the neck as possible, then on a 22 fret guitar it will invariably end up somewhere around the 24th fret position. But that doesn't automatically mean there's something about the harmonic correlation of that pickup position - it just happens to fall that way.

I would think it is more to do with both tradition and aesthetics. I'm willing to bet the neck position was chosen largely because it looked good, added symmetry to the instrument and provided a good tonal contrast to the bridge and/or middle pickups where applicable.. If you moved the neck pickup closer to the bridge leaving a large gap at the end of the neck while leaving the bridge pickup close to the bridge, I think most people would view it as being 'lopsided'. That the neck pickup traditionally ends up at or near the implied 24th fret position on a 21/22 fret guitar, in the absence of confirmation from the manufacturer that the intention was to somehow capture one particular harmonic, in my view is coincidence. Positioning a pickup to capture a specific harmonic node/peak is an impossibility on a fretted instrument. Positioning a pickup to satisfy an overall tonal characteristic, however, is entirely valid.

Think you mean neck pickup? The concept that pickups were deliberately positioned by Fender, Gibson etc based on a particular harmonic relationship is unsubstantiated. Articles like that provide no references to back up their claims. As builders all we really need to be aware of is that moving the pickup further away from the bridge makes the resulting tone warmer, and whatever aesthetic decisions about the look of the guitar are satisfied.

The diagram that Biz shows is the one you want (thanks @Bizman62 ). The second one he links to will also work- it's taking the same switch but kinda utilising it back-to-front.

Actually, scratch that. The photo of the switch you're using suggests it will not work if you just follow the original diagram as-is. There's some transposition you're going to have to do to make it work. It's late in my time zone. Assuming no-one else manages to pick this up I can whip up a revised drawing for you in the morning if you like.

Compare your latest sketch with the original diagram - you have got the bridging between the four lugs mirrored.

Looking at the schematic, the minimum controls you need to engage to get sound out is any one of the three pickups and the 'M' switch. Solo and Acc can be disengaged at it makes no difference. By your description, 'Solo' just mechanically pops out the 'Acc' switch, whereas 'Acc' just engages the low volume rotary pot. Maybe to differentiate that they're the higher resistance of the three in the factory for the guys on the assembly line putting it together? Could mean anything. But probably not anything significantly important from your perspective.

Ah, yes - that makes more sense, It acts as a 'cancel all' rather than to enable some part of the circuit. Could that skinny black wire that's lacing underneath the two capacitors be rubbing through the insulation and making contact with the bottom leg of the left-most capacitor? Seems kinked over a little tight. Generally looks like a pretty grotty circuit board, but probably typical of something of its age. I'm not too keen on the way that black foam material has reacted with the board. It could do with a bit of a clean with some isopropyl alcohol. Easiest way I can think of the check the bridge pickup is to desolder the lead from it off the PCB and connect it directly to the tip connection on the guitar lead and see if the sound becomes more normal. That would at least tell you if the fault is with the pickup or with the circuit.

It was probably done that way as the intention would be that the 'Acc' setting would be used as a preset lower volume compared to the other settings. The 50k Accompaniment pot would load up the master volume and provide a degree of automatic volume cut when engaged so that the guitar player could duck behind the other band members when it was time for him to stop doing his Jimi Hendrix impersonation and let the organ player do his best Keith Emerson. Swapping the order of volume/Acc pots would mean that the overall volume would never be any louder than what the Acc pot would provide when set at maximum, which defeats the purpose of the circuit. You could use the volume pot as the Acc pot, but it would have all its adjustability in the first few degrees of rotation near 0-2 (ish), and then no perceptible difference from 3-10. Repurposing the Acc knob for master volume is worthwhile however, especially if the regular Volume control has that esoteric lever-and-gears arrangement. Exchanging the Acc pot for 250k and re-wiring it to utilise this pot as a master volume instead is possibly good practice simply because (as you say) finding a replacement assembly for the normal Volume mechanism will be nigh-impossible. You could then either leave the lever-and-gear pot disconnected, or wired as the Acc control (and accept that its volume-drop preset function will not work quite as originally intended).

A pickup with weak magnets could do that. A quick check would be to attach a screwdriver to the pole pieces and see how well it 'sticks' to them, and compare with the other two pickups. Your resistance measurements seem reasonable for a generic single coil, so my gut feel is that the windings themselves are ok. Removing the pickups would be an idea to see if they are marked in any way to indicate that they might be intentionally different. How confident are you that the schematic is correct? The 'solo' switch does precisely nothing as drawn. For that matter, how confident are you that your guitar matches the schematic? Some of the faults you list (pickup sounds, HML switches not working) could be down to wiring mods/wiring errors/sins of the past.

Correct - he's truncated the initial 12th root of two, not rounded it up. If he'd used r = 1.0595 the calculator would've provided more accurate results, and his disclaimer on his webpage that there's rounding error in the tables would be more relevant. R = 1.0595 gives a constant of 17.808, which would yield a 12th fret position of 17.007" from the nut. We're splitting hairs, but it explains why the difference is there.

There's a related article on Mottola's website that compares fretboards slotted to the modern 17.817 factor against the traditional (pre-calculator) variant, where the constant used was simply 18. If you scoot down to the graphs and compare the green cross points (rule of 18 with intonation compensation applied) vs green diamonds (17.817 with compensation) for each string they're extremely similar. Probably within a couple of cents at their worst, and certainly questionable as to whether a regular hooman could detect the difference if played side-by-side. Based on the info linked, the difference in fret placement using 18 vs 17.817 seems tiny. I've personally not built anything that might compare the two, but I would think that fret placement using 17.835 and 17.817 would result in even less intonation/pitch discrepancy still. Bottom line: both the Stewmac and Tundraman fret calcs produce perfectly acceptable fret position results that work, even if the numbers don't quite line up. Entirely up to you as to which one you pick.

It's because the Tundraman website uses a less-common divisor when calculating the fret spacing. The 'modern' way of doing it is to use the twelfth-root-of-two method which places the twelfth fret at exactly half the scale length (17" in your case). This gives an initial divisor for placing the first fret of 17.817, Ie, if you divide the scale length by this number, the result is how far away from the nut the first fret will be (34/17.817 = 1.908"). Working out the remaining frets is just a case of subtracting the sum of the previous frets you calculated from the scale length and repeatedly dividing by 17.817. The Stewmac calculator (and FretFind2D, LMII and many others) uses this method. For some reason (which is a bit naughty of Tundrman for not disclosing) he's used 17.835 as the common divisor, and then erroneously explained away the discrepancy in the calculated results on his webpage as '...rounding errors...'. Using the above divisor will still work and give playable results, but it does look odd if you're trying to compare the results of the two tables, Liutaio Mottola has a good explanation of the various methods of calculating fret placement on his website if you really want to get heavy with the math. As an example, below are the differences when calculating the fret positions using the two divisor values of 17.817 and 17.835 on the first 12 frets at 34" scale length in a spreadsheet. The Stewmac results agree with column 'C'; Tundraman in column 'E':

Ground it wherever you can then. All it needs to be is conductive to the strings in some way. If the strings are in contact with the metal tailpiece, and the tailpiece is in contact with the metal body, then that's your path through. Grounding the metallic body (either with its own dedicated wire or by way of trying to get to the tailpiece) would also be good, as it provides shielding to the rest of the electronics.

Is the neck bowed or is the top collapsed? Both result in excessive action but require different approaches to correct.

I think the idea that the zero fret needs to be tuned in such a way that the string angle behind the fret equals the typical angle exhibited when fretting any other fret (as per Roger's comments linked above) is possibly over-thinking the implementation of it, but to each their own. I've used zero frets for a few years now and I think their benefits and ease of installation far outweigh the effort in installing and fine tuning a traditional nut. At the very least I'd encourage everyone to at least give it a try. I've often wondered why there's even a discussion as to whether or not a zero fret wears quicker than other frets. We don't seem to have the same issue with wear on a bone or plastic nut, and presumably being softer material than the frets they should wear faster still. It may be possible that (perceived) rapid wear on a zero fret is exacerbated in situations where the guitar has a trem and/or a traditional headstock, and the strings can slide across the face of the nut as they are tuned/detuned. Brian May would have gone through thousands sets of strings on the Red Special and is known to uses his trem fairly judiciously while playing. Perhaps the wear is more as a result of the strings 'sawing' through the zero fret rather than sliding across the crown laterally (eg, finger vibrato). I'd be curious to see what the wear on a zero fret on, say a headless guitar would be in 20-30 years, where the string cannot slip over the zero fret much because it's so short and only really exerts downward pressure on the crown.

Epoxy would be my guess. PVA wouldn't adhere to the plastic. CA might work but would be more expensive by volume, plus I wouldn't want to be exposed to the fumes while trying to glue it all together for any length of time. I'd be a bit concerned about the potential for wood movement due to climatic changes. Plastic won't move at all due to changes in temperature, humidity etc, whereas wood can do. That could lead to strange warps or twists in the neck as the two materials fight each other, or worst case the glue join(s) between the two materials fracturing. Maybe save it for the body only? Interesting visual idea though Shine some LEDs up the length of it and it would be pretty striking in the dark.

Can you describe how the wire colours on the pickups you ordered differ from the ones shown in the diagram? As @henrim indicates, they should be a match if they're both Dimarzio's.