Rewiring an Incomplete Vintage Guitar

[sambafirefly]

In the midst of COVID, I'm returning to an old project of refurbishing an old... well something. I can't identify the instrument, I can't identify the pickups, the circuit is unusual, and worst of all the circuit is incomplete. I don't know enough about circuits to fill in the blanks, so I'm looking for help on the project. I've got a drawn diagram of the circuit here, including values of the pots and the cap. Note on the underside of the pickguard claims to identify the three wires coming off of each pickup, but I don't have a baseline to confirm one way or the other. I'll include a few points I've noted down --

1. The pickups have 3 output wires, but they're sized like single-coils, the pole-magnets are centered, and the bobbins are completely sealed in a metal casing. The note inside the casing claims that the blue wire is ground and that black/red are the coils (plural).
   
2. Pickup selection runs through two SPST on/on switches -- two positions, three ports. The upper pickup is fully wired, and I have a sneaking suspicion that they're meant to mirror each other and that the third ports either go nowhere or direct to ground.
   
3. The volume pot is obviously missing output from the second node to the tone knob and the tip node of the output jack. Maybe missing another input wire from the lower switch???
   
4. The tone knob has me totally stumped. I have no idea why the third port is wired correctly and the first two are soldered together, connected to the cap, and then run to nowhere. I'd be much more comfortable just redoing the whole thing as a typical tone knob if that's an option here.
   
5. Ground wire for the bridge was included and wired through the jack ground node and grounded to the back of the tone knob.
6. My Green wire to nowhere isn't actually a part of the circuit. I suspect that, if it were actually needed, it would be wired to the first node of switch 1.
7. For reference, the values of the components are: 500 Ohms Volume Pot, 1k Ohms Tone Pot, 0.047 Microfarads for the cap. I'm a little impressed at the size of the pots, but nothing too out of the ordinary.
   

It would be really nice to be able to wire this Frankenstein through two DPDT on/off/on three-way switches at some point, but for right now I'd really like to try to restore what was once there. Any circuit wizards out there able to make sense of this?

[thetragichero]

hello and welcome to the forum!
got any pictures of the guitar, pickups, innards, etc? they might be helpful in identify what we're working with

[newey]

Yes, some pix would be helpful. But, a few points:

First, the blue wires are quite likely shield wires, not signal carrying. I strongly suspect these are single-coil pickups, with the red and black wires carrying the signal, and the blue wires as shields (which would then always be connected to a grounding point. The wording you describe seems to confirm this, but checking the pickups with a multimeter would tell the tale for sure.

Second, you are correct that the tone control is wired strangely/incorrectly. Input to the pot should come from lug #1 on the V pot to lug #2 on the tone pot, and the cap should be wired to ground from lug #3 (there are other ways to wire it, but this is the most common). Lug#3 on the tone pot should not be wired to anything.

Third, you definitely need a wire from Lug#2 of the volume pot to the output jack tip.

Four, your text as to the values of the pots doesn't match what you have on the diagram. Which values are correct?

As for the pickup switching, S-1 seems fully wired, and in one position, the pickup (looks to be the neck on your diagram but not actually specified as such) will be "on", and in the other position, the red and black wires are shorted together so that the pickup will be "off". S-2 looks (I emphasize "looks" as it is not entirely clear)as if it puts the second pickup in series with the first. (Old Teisco guitars were wired this way, as were old Danelectros and some others). So, with S-1 "off", S-2 would then turn the second pickup on/off. With S-1 "on", S-2 would give either the first pickup "on", second pickup off, or both pickups in series. There would never be an "all off" setting.

But this is just some semi-educated guesswork on my part. we'll need more info as TragicHero suggests

[newey]

sambafirefly-

And, I'm forgetting my manners:

Hello and Welcome to G-Nutz2!

[sambafirefly]

So sorry, I ought to have included the pics at first. Added to the OP along with the guitar body. My repair-guy was able to identify it, but that was a few years ago so I've forgotten what it's supposed to be. Sadly I'm told to expect the guitar to sound like a bad beginners guitar, even though it's obviously vintage.

I'd be happy to check the pickups with my multi-meter, I'm just not entirely sure what I ought to be looking for. I'm guessing that if red/black are the bobbin coil I ought to be able to test a resistance across the two. If the blue wire is shielding or the baseplate, what would that render?

As for the value of the pots, I haven't measured them directly, but they're labeled 50k/100k. I guess I just naturally translated that to 500/1000 just because I can't really imagine 50k and 100k would work at all with such a low voltage as is present in a guitar circuit... Guess it's high time I pulled out the old multi-meter to confirm what little I can about this mess.

[newey]

50KΩ and 100KΩ would be odd values. The guitar is clearly late '60s Japanese, there were a slew of brand names but only a few manufacturers, principally Kawai and Matsuoka. It might have been branded as a Teisco, it might have been a Kingston- essentially the same guitars were sold under multiple brand names.

Steve and the guys at the VintAxe forums might be able to help with a definitive ID, which might then lead to a wiring diagram. But your pictures reaffirm everything I said above.

[newey]

I am not guaranteeing that this is how your guitar was originally wired. Caveat emptor, and all that. But this is a diagram for a Teisco E-200 (and other models). It isn't exactly what I described above, but I'm fairly sure this was what was on your guitar originally. Here, the two switches give neck and bridge together in series, or either pickup by itself, or both off.

Even if this is not the exact wiring originally in the guitar, you can certainly wire it this way and it will work just fine.


(Sorry for the crappy image, I had to enlarge it quite a bit.) Also, notice that both pots are specified at 500K.

[sambafirefly]

Thanks a bunch Newey, I'm impressed! I've played for almost 20 years now and built a number of kits, but I'm frequently surprised by just how much I actually don't know. I'll trot on over to vintaxe and see what they can figure. As you say, it looks closest to the ET-200 Tulip, but not quite there. I don't think I would've guessed that it was over 50 years old.

Sadly, the instrument came without a bridge and the tuners are missing a gear, so I'm replacing them with modern equivalents. Tried to get as close as possible to the same look on the old tuning heads as I could, but the bridge has to be a typical Tune-O-Matic. Should install just fine -- I measured and matched the string spacing of the tailpiece, and the instrument is obviously a 24" scale -- but it isn't going to be totally authentic. The positive is that the instrument was just handed to me for nothing, so I should be able to get it playing for about $35. Not bad for something that would typically sell for $150. At some point it'll need to be refinished, and perhaps re-fretted, but projects for another time.

[thetragichero]

better bridge and tuners, a nice setup, and a fresh rewire and I'd say this would play better than a "toy guitar" as you were told
my guild i just finished breathing new life into was originally a student model, i believe (mine is full 24 3/4" scale... which is toy like to me as I've always played strats... some with the same model number were 3/4 size and its nickname was "the freshman"). plays and sounds great now
at least as of a few years ago, old teiscos etc had quite a following in some circles. and my 80s mij ibanez basses are KILLER

that is all to say that this is a worthwhile endeavour and you might just be pleasantly surprised
keep us updated!

[reTrEaD]

Mar 30, 2020 23:42:40 GMT -5 sambafirefly said:

It would be really nice to be able to wire this Frankenstein through two DPDT on/off/on three-way switches at some point, but for right now I'd really like to try to restore what was once there.

Hi sambafirefly ,

The original wiring had the pickups in series and each switch shunted its pickup to turn it off. If you wanted three-way switches (to select On / Off / Out-of-Phase) you might be able to accomplish that with DPDT on-on-on switches, but I don't think you'll find them in slide switches.

But you could use DPDT on-on switches and wire such that you no longer have a 'both off' selection. That would result in the four possibilities being:
- Both pickups in series
- Neck only
- Bridge only
- Both pickups in parallel

---

The Japanese guitars of that era were flat-out awful. Some used bridges with fixed saddles making intonation adjustment impossible. Others had adjustable saddles which rattled and buzzed. The tuners were of poor quality as were all the hardware, including the pickups. The 'hoop' which functioned in a similar fashion as a string tree was a binding point, causing severe issues with tuning. The tremolo system also was prone to tuning issues.

If this guitar was fully intact, I would have suggested trying to restore it to original condition, as the value to a collector would be greater than any value as a guitar to be actually played. But since parts are missing and I suspect the front of the headstock may have been sanded to remove the finish (many of the Japanese guitars of that era had painted headstocks), it won't have any value to a collector.

The 50k volume and 100k tone pots don't surprise me. Those values are quite low, but the manufacturers of budget guitars in Japan during that era were pretty much clueless. I'd suggest replacing those both with 250k pots or 500k, right from the start.

If you're doing this just for fun and to get some experience, then by all means do it. But the results will be less than stellar. You'll have a much more playable guitar if you bin this and find an old Squier that needs a little love and use that as your starting point. JMO.

[newey]

You'll have a much more playable guitar if you bin this and find an old Squier that needs a little love and use that as your starting point. JMO.

My opinion as well. I started out playing a Japanese guitar of roughly the same vintage, and all of the issues RT mentioned were true. The one he didn't mention was the baseball-bat-ish neck profile. But if your modifications can at least make the tuning stable, well, that's probably about the best you can hope for.

As the 1970's progressed, the Japanese guitar manufacturers really got their act together, just like their car manufacturers did. But in the late 60's, not so much. The pickups from some of these older Japanese guitars are highly prized by some folks, for reasons not apparent to me- maybe it's just because they are something different than the usual fare.

I could almost swear that what you have there is identical to the guitar the lead guy in my 8th-grade garage band had. Like his, there was no logo on the headstock (and, contrary to RT, it was unpainted). As I said, these things often were sold under multiple brand names. Sometimes, they didn't even screen-print a logo, they'd just put a sticker on the headstock, and those usually lasted until the first sweaty jam session on a humid summer day.

That guy became an excellent guitarist, and quickly upgraded to a Hagstrom.

My best guesses as to brand names: I don't think it's a Teisco, they had a distinctive look. It also doesn't look like my old Norma. It could have been sold as a "Kingston" or as a "Kent", it seems to look like those (they were the same guitars). Sears sold similar guitars under the "Silvertone" brand, you might look for old Sears catalogs online (1967-1970) to see if there's a match. Sears main competitor back then, Montgomery Ward, sold guitars under the "Airline" brand, but it doesn't look like any of those. I think JC Penney used to sell cheap Asian guitars back then as well.

Often, the brand would depend on whether the guitar was purchased in the US or the UK (or elsewhere). The same guitar models would be imported to the UK with one name, and to the US under a different brand name. Often, the distributor/importer dictated the name.

EDIT:Also, RT is right about replacing the pots, not only because of the values, but because pots are mechanical and wear out over time- they get scratchy and noisy as you turn the knobs. Sometimes a good spray of contact cleaner will fix that, but pots are cheap and if you're doing all this other stuff anyway, might as well replace them.