P90 conversion

[antares]

OK so here goes.



I have this Gordon Smith that was incorrectly supplied with a humbucker. After 30+ years I have decided to retro install the P90.
I have a 1970s Gibson P90, the type with the transparent bobbin. I have questions about the P90 installation too, but first I have had to re-jig the wrap around bridge. The original compensated effort had been installed as though it was intended to be a left hander.

I bought a Tone Pros intonatable wrap-around. When I installed the Tone Pros, I filled the counter bores with DevCon and counter bored the DevCon filler on the radial at work, but it was (obviously) not satisfactory. Under string tension, the posts lent forward and the high gloss exaggerated the appearance of leaning forward. Looked like a mules hind leg!

So, I pulled the bushes and counter bored the holes again (without chipping the lacquer!) and procured some oak dowels from eBay.



You can see the dowels here, not yet cut to length. The dowels are a really snug fit- at the bottom of the holes, but there is a little play (0.015") around the top of the counter bores. I bought some TiteBond from eBay, but I'm not sure whether, given the gap mentioned- TiteBond is a suitable adhesive. Please don't anyone suggest making the counter bores any larger and buying larger dowels, the TonePros. bridge only just conceals the work as it is. This is the last chance saloon!



Would Araldite be acceptable? I have access to Redux 410 too which is awesome adhesive.


e&oe

[Deleted]

Here is how I would fix it. Cut the dowel down to size as close to the top as possible. Before gluing in, I would use some of the wood form the dowel and make some saw dust. Mix the dust in the glue and use it as a filler. Let dry for 24 hours then sand smooth. Re drill for the new bridge.

there is a guy here in town that truly I think he over thinks stuff when it come to fixing guitars. I find in most cases that titebond glue works. I also will use CA glue for some repairs. But the guy I'm talking about uses a lot epoxy stuff for his repairs. It looks like JB weld to me. It gray in color, and he uses it all the time. But we are dealing with wood not metal. Today's wood glues work really good. Plus I think wood glue is more forgiving when It come to things like plugging holes.

But, everyone has their thing that works for them. I like CA and wood glue over anything else. guess you could use a little wood filler too. But wood filler over time shrinks up.


EB

[antares]

Thanks Eddie. I need to sort the bridge before looking at the P90.
Another thing I've noticed is that the 3/8" unf stud threads are an extremely loose fit in the bushes. This can't be helped (although it lets down the otherwise excellent engineering of the TonePros bridge.) I reckon that once the studs are threaded down that far into the bush it shouldn't affect the vertical nature of the studs too much, but I'd prefer a tighter fit to ensure better transfer of vibrations.
More later...

e&oe

[antares]

All done now!




She's a beauty!

Actually, there is very little signal emanating from this guit fiddle. The sound coming from the amp is barely louder than the instrument played without amplification. However, it is loud enough to establish that the '50s wiring that I deployed is working (the pots work as intended).

The pick up is a transparent plates late '60s soapbar Gibson. I switched the base plate with an Artec dogear one, and my 40watt Weller TCP iron was not man enough to solder the pickup braid, so I went in with a Weller 100watt soldering gun.

Since I am a radio "ham", I was well aware of the large magnetic field that these devices generate, but I reasoned that if I did not withdraw the gun while it was active, there should be little risk, and if anything could in fact re-charge the Al-Ni-Co-5 magnetic bars. It does appear that since it is very weak in output that I may well have de-gaussed the magnets, but this is reversible. OTOH, the pole pieces definitely exert a reasonable pull on a ferrous item such as a screwdriver.
Perhaps I simply loused up what is a very simple circuit?

The mod is completely reversible back to the humbucker. The dogear screws are decorative (being filed down 6-32 unc that are self tapped into the pickup base plate fingers.) The dogear base plate fingers are trapped between the spacer and the plastic cover. This means that the two screws in between the pole pieces holding the pick up down do not need any springs, but I put one in anyway. The purpose of the spring is to ground out the 1/4" plate brass screwed to the bottom of the hum bucker rout.

The depth of this rout was too great to use standard P90 soap bar screws, so I used m2.5 cheese head machine screws threaded into the brass plate. It sounds like a dog's dinner, but it works very well and you'd never know if not informed or had an opportunity to scrutinise up close.

I purchased this pickup from a Canadian seller on eBay. Soon after, John made those lovely P90s and I gnashed my teeth reading those postings while waiting the two months it took for the pickup to arrive. Even at the time, I wished that I had heard of John's pickup prowess before I bought the eBay one. Hey-ho. No tears. Spilt milk.

The effort was worth it though. This guitar was a custom order in 1980 (or thereabouts) that failed on so many counts, but primarily the incorrect pickup. It now has Sperzel locking machine heads and a TonePros wrapover, all in my preferred nickel plate finish. Gordon Smith guitars are worth checking out. They are more than a match for Gibsons. They are made by a man from the north west of England called John Smith. My one is serial number low 300s but they must be well over 25,000 by now. John Smith is a left field thinker. He puts truss rods into one piece maple necks without a skunk stripe. A trade secret! Also, he had a 12 string that had six machine heads each of which had a ball end threaded through in addition to the normal string with the second group of strings adjusted by mini tuners on the bridge.

What do you think about those magnets John?

Steve.


e&oe

[dnic]

Very, very nice. I've never built an LPJ but I really like the look and have been pleasantly surprised by the sound as well.

Not to rub salt in the wound but the split P90s (he calls them 45s) John built for me sound great. If I could play better I'd do a demo. Heck I might anyway.

[antares]

I originally purchased the guitar because I wanted a double cut LP, but back then I didn't really know what it was called and hence what to search for. Nowadays, we'd just google it but back then...

I love the idea of tapping the P90s. The original volume pot had a piggy back switch to split the two coils of the humbucker. I swapped that and the tone pot out for a pair of log 250k CTS pots. I used an "orange drop" .047 mF cap but I don't buy into the stuff about mojo regarding different types of capacitors. Others would disagree strongly though.

e&oe

[Deleted]

Looks really good.
I had this customer that bought and brought me a neck, bridge and a T-stile body over a few weeks ago and asked me to put the neck and bridge on the body for him and he would do the rest. The body was precut for humbuclers. He bought some SD p90's for it. He brought it over the other day so I could see it. WOW! I now want to build me a Tele thin line with two p90' in it.
I bet your guitar sound awesome as well. I'll see how spring goes, If I get to feeling better by then I may build me a neck through tele, or I'll buy a body off line and put one together.

EB

[antares]

Thanks for the comments, but of course I did not make the guitar! I only modded it.
This instrument has a very comfortable slim neck with low and wide frets. It shouldn't work but it does and is a supremely comfortable instrument to play.John Smith is renowned for making instruments that "get the job done" with no fuss and no bling. They are reliable working musician's tools.

As far as sounds go; it was good enough before, but I wont be in a position to judge until I've figured out the no output problem. John Smith's wife winds (or at least she used to wind) all the pickups. They are well regarded too.

e&oe

[GuitarAttack Forum]

Great guitar!

Yes, the soldering gun will degauss, or de-magnetize pickup magnets. Personally, I don't like to get soldering guns anywhere near a guitar.

The dual-sound P-90s I make have been pretty popular. I am making a set for myself right now to install in one of my development guitars.

Again, great job, and thanks for sharing.

John

[hoz]

I missed this thread entirely! I'm trying to catch up on my GuitarAttack intake, ha.

This looked like a clean fun rebuild. Congrats on converting a guitar originally intended to have a p90 back to having a p90!

Next time you need to plug post holes, I would recommend those bits that cut out tapered plugs. The best thing about those bits, is making a plug with similar grain. They are easier to drill straight and are probably more sturdy of a plug. Nothing wrong with dowels though.

I recently installed TonePros posts on my SG Special wraparound bridge, and was impress. No leaned over bridges.

[antares]

Hey Hoz,
I emailed TonePros about this and they asked for photographic evidence. If I take a picture of the dogleg reflection- they'll just think that the hole was bored incorrectly.
I tried a 3/8-24 cap head bolt in the bush and it was a nice snug fit. It follows that the threaded post is incorrect. Sure enough, my Starret digit vernier reveals that the threaded post is .003" smaller over all than the 3/8-24 bolt. (this was an MS16998 aerospace bolt that I got from work made to tighter tolerances.) Perhaps the plating allowance was incorrect? I would need a video of the post being wiggled in the bush to prove my point to them. It's a real pity because the TonePros gear is first rate. I must have lucked out with a Friday afternoon example! I am going to try a "thin nut" (again from work) to see whether I can lock the post vertical. At the end of the day, it doesn't impact on the playability, it's just frustrating when you pay top dollar as opposed to bargain bucket.
Steve.

e&oe

[hoz]

I believe my posts had a bit of slack in the threads also. Under string tension I was happy with them since the bridge itself didn't roll forward.

From a ebay supplier I used to get posts the had an allen screw poking thru the bottom of the post. It would put tension on the threads when tightened up. It didn't help with bridge roll though! They do not have any more of those (just checked on ebay). I know they were made in Korea, and were $7 a set. I wish I bought a few more of those!

[antares]

With all the minor hurdles that I've had to leap over to perform this reversible mod, I've elected to live with the wonky posts Hoz.

Regarding the lack of audio, I read on the internet that the magnets have to be connected with similar poles facing each other. I dismantled the pickup and confirmed that the magnets are correct, and somewhat happily have not been affected at all by the soldering gun onslaught.
The pickup still rings out at 7.9K. The controls both work as intended. It all looks wired correctly (it's such a simple circuit after all) All the connected pot shells ring out. The circuit from the pickup hot lead to the jack tip rings out, and all the grounds ring out to the back shell OK. So, I clipped the guitar lead to the pickup wires and C-R-U-N-C-H!!!- I forgot how much I'd turned everything up to get a whisper out of it!
So, since the controls work as intended, I must have one or more dry joints. Tomorrow I shall make free with the 40 watt iron. Fingers crossed.

e&oe

[antares]

OK, the axe had (has) an amplifier type instrument input (guitar output) socket with three terminals. The third terminal was not easily visible in the Lester type wiring rout, and I wired to the shorting tag by mistake. There was nothing wrong with the magnets after all. This meant it rang out fine UNTIL you plugged it in and hooked up to an amp. So confusing and such a simple fault?
Oh boy I do love this old Gibson P90. A colleague has me gassing for a P13 now...

Makes me wish I'd left off for a couple of weeks back then. EB's build thread with John's P90s left me drooling!
This P90 mod has made the guitar spring into life. It should never have been supplied with a hum, and I ordered a P90 so I was let down big style.

All's well that ends well!

e&oe...

[Deleted]

Ha! I wish I had made the guitar with the P90's in it, but that was Dane.
wiring at times can be a pain in the butt. Wait until you wire one up and nothing is working right, and you go over it a few times, and still can't get nothing to work, then you find out there was a brake in the wire... LOL!
EB