Seeking help. Lets re-wire a Starfire bass!

[lungimsam]

Sounds great!!!!

 

[mellowgerman]

Sounds like a recipe for success!

 

[zulu]

Update:
I received all the new parts for the re-wire and went to work. This was my first full wiring change, and my soldering is barely passable, so I guess some troubleshooting is to be expected. More on that in a moment...

First, here's a few shots of the existing wiring and some views of Starfire Bass construction not normally visible

As you can see, the wiring was a complicated mess from the start that was further modified. After removing or clipping everything I didn't want, I assembled and installed my new harness. It took quite a while with my poor skills, but everything got connected. New blend pot, volume pot, tone pot and cap, and input jack.

So, the results are in: everything works as intended and the tone will be great, but maybe you can help me chase a few gremlins.

1. I'm getting distortion when the tone knob is more than halfway 'up'. from either pickup or both. I'm worried about the tone pot because after connecting and installing, the pot was stuck at the full off position, and it took some wiggling to free it up. I was afraid maybe I cooked it with the soldering iron. I never tried turning the pot during the install.

2. The pickups are out of phase in the middle position. This surprised me since the coaxial pickup leads are impossible to misidentify the ground. Anyway, I guess I can just swap the polarity on the leads from the bridge pickup to correct this?

3. There was an additional wire coming out from the route to the neck pickup. I assumed this would be a part of a common ground but it didn't have continuity with the bridge or any other grounds. Being an assumer, I went ahead and soldered that wire in with the other common grounds. Could this be something else that is causing distortion or phase issues?

As soon as I sort these troubles, I know I'll be very happy with this mod. Super simple and pure tone from the Bisonic.

Thanks in advance for any tips!

 

[mellowgerman]

As you may already know, those pickups being out of phase was not an uncommon quirk for electric Guilds. In order to properly address this, you will have to separate the ground (-) from the shield on one of the pickups, which will most likely have to happen at the pickup itself. That being the case, I'd be willing to bet it will be easier to make that modification at the Bisonic. In my experience, covered humbuckers often have the ground and shield connected inside the shell and would require some dissection. The Bisonic should have two clear terminals on the bottom of it and you'll see that one of them is also soldered to the chrome shell of the pickup. You'll want to disconnect the (-) terminal from the shield there, probably move the main wire that was previously your hot (+) to the other terminal (so that it is still shielded by braided shield wiring) then jumper what was previously the hot (+) terminal to the shield.

*may go without saying, but please be extra careful when soldering at the Bisonic pickup's terminals, since overheating there could cause serious damage to the pickup. With a pot it's not such a big deal since it can be easily replaced if damaged.

I hope that makes sense! I never got formal electrical training from an expert, all of my knowledge on the subject comes from years of reading and experimenting, so my terms and descriptions may not always be the best written instructions!

Regarding the distortion you're getting, it may very well be the symptom from an overheated/damaged pot, but could also be a bad ground, so I would start by double-checking your ground solder joints. I've had static/distortion happen from a poorly soldered connection.

The additional wire coming from the neck pickup cavity is likely a connection to the little transformer that's typically underneath the Bisonic, which is a part of the tone suck circuit. If I'm right about that, you don't need that connected anywhere, but I don't think you'd run into any issues if it's just connected to ground.

 

[lungimsam]

Distortion:
Only suggestions I can think of if the tone pot isn't trashed is:
Pups look too close to the strings. Move them down til they are 5/32 from bottom of strings when pressing strings down at last fret. Might have to remove the black pup ring to do it on the Bisonic.
Also, try reversing the white signal wire and the cap wire on the tone pot so the signal wire is on the 3rd lug of the tone pot (where the cap wire is now) and the cap wire is on the middle lug (where the signal wire is now.).

Out of phase sound:
Maybe is "comb filtering" nasally sound when both pickups are full on. Just rotate the blend knob to the left or right slightly and should get rid of that phenomenon if that is what it is.

Tip: when soldering and unsoldering from the Bisonic terminal studs that are sitting in the holes in the plastic surround (if that is the case with the vintage Bisonic, as it is with the BS-1 Bisonic) you may be able to lift the metal terminal studs out of the plastic holes, solder , then put the studs back into their respective holes after cooling. I removed one from it's hole once and put it back. If you can't take it out becareful cuz once that stud gets heated up the plastic hole will start melting. But I really cannot comment on the vintage Bisonics with that transformer because I never worked on one of those.

Also, anything you will not be using just remove from the circuit, like that transformer that mellow german is talking about (if poss to use the Bisonic without it,). Just get it out of the equation to help trouble shoot your issues.

Last, looks like you still need a ground jumper from volume pot shell to tone pot shell. Maybe run that bridge bare ground wire to the volume shell, then along to tone, then only have the existing black ground wire on that tone shell run to ground lug of output jack.

I'm not familiar with that blend pot so cannot comment on that.

 

[mellowgerman]

Tip: when soldering and unsoldering from the Bisonic terminal studs that are sitting in the holes in the plastic surround (if that is the case with the vintage Bisonic, as it is with the BS-1 Bisonic) you may be able to lift the metal terminal studs out of the plastic holes, solder , then put the studs back into their respective holes after cooling. I removed one from it's hole once and put it back. If you can't take it out becareful cuz once that stud gets heated up the plastic hole will start melting.

There were variations in vintage Bisonics, but all Hagstroms that I have seen, that Guild used had the terminals attached to one of the paddles, like the one pictured below (original to my 1970 Starfire). Sidenote, I have seen Bisonics from Hagstrom Coronado/Futurama models that had no poles, but just the red and blue wires coming out of the bobbin, going directly into the shield-braid, along with a 3rd green shield wire directly connected to the paddle... so it's possible that configuration could also have found its way into an early specimen Guild.

 

[lungimsam]

Cool info mellow!
That’s a way more sensible setup than the Newark Street BS-1, which has terminal studs implanted in plastic molding.

 

[zulu]

@mellowgerman and @lungimsam ,

Can't thank you enough for the very helpful input! I have some good progress!
I guess from being lazy, or just not wanting to disturb anything else, I had never pulled the bisonic. As Mello predicted, there's a little transformer underneath. That was my third wire from the neck. I went ahead and pulled the transformer out. I decided not to try flipping the phase.

I also checked my other grounds and jumped an additional ground to the volume pot body. I removed the spacer under the bisonic as it had always been a little too close since the de-fret. Put it back together... no distortion! Just great tone. I love it. I may revisit the phase issue later, and the tone pot works fine, just doesn't turn perfectly smooth. If it bugs me enough I'll replace it.

Now I have to think about knobs, and what to do about the route from the center pickup. For now I had a little piece of wood to cover the hole temporarily.

For now I'll play the heck out of it and see which annoyance needs to be fixed.

Thanks again for the help!

 

[SFIV1967]

Just a question, maybe it was answered but I missed it. Is the bridge grounded, means are the strings grounded? Often that wire get lost during such changes in the electronics.

Ralf

 

[zulu]

Just a question, maybe it was answered but I missed it. Is the bridge grounded, means are the strings grounded? Often that wire get lost during such changes in the electronics.

Ralf

Thanks for bringing this up Ralf. I saw no evidence of the bridge being grounded. Only possible way I could see is if the bridge is connected to the ground of the bridge pickup. There's no other holes from the center block into the wiring cavity.

I might not notice string grounding issues with these tapewounds, though!

 

[zulu]

On a sidenote, the Patent sticker on that guitar humbucker almost looks like it originally read 2,737,842... in which case: https://reverb.com/item/63194524-vi...or-your-les-paul-burst-conversion-restoration

That said, I was never interested enough in those Gibson PAF humbuckers to fully research what kind of Patent # variations there may have been and what those would mean for it's value and origins. Anyway, maybe worth looking into!

BTW That is a Gibson T top patent number pickup I pulled out of the bass. Might be worth a hundred or two. Getting ready to list it on ebay though I'm half tempted to try it in the nightbird.