Guild M65 - Upgrade Pots and Pickup

[JWMandy]

I have a Guild M65 3/4 guitar. I bought it to play. Decent condition, all original parts. I'm NOT a collector, and it's cheaper to upgrade than buy a NEW guitar in the same size. Some tell me, "Don't touch it for the collector's value", but as stated I'm not one. Pots make an annoying hum.... which could simply be a solder issue (though I'm not a EE and qualified to make the judgment). Old electronics date to a 1975 build. This is later than a usual collector is interested in from what I read here. Thoughts? Let's say I save the original parts in the event some day when I ding dang, someone wants the original parts back.... am I crazy?

[nevershouldhavesoldit]

They were cool little guitars for sure! Unlike most "student models", they were just smaller versions of the full sized, full scale M65. From the old Guild catalogs I have, it seems to have been made only from 1959 to 1968. The pickup (which, along with the pots and wiring, is the same in both full and 3/4 size M65s) is a Guild single coil unit. As I recall from my high school days, they were as noisy as the Fenders of the day. So unless it was quiet when you got it and began humming all of a sudden, I suspect the noise is probably endemic to the model. And if it was quieter before and is now noisy, something probably broke - solder joint, ground wire etc. Simply changing the pots is probably not going to fix a hum. If your pots have 1975 date codes, they're not the originals. So the replacement work may have failed, e.g. a solder joint is cold or broken.

The best way to find a cure for what ails ya' is to make an accurate diagnosis. There are many pertinent questions to help you figure out what's probably wrong. Does it hum all the time, through any amplifier in any location? Does the hum change in character or loudness when you turn either pot up or down? Does it change or go away when you touch the strings or any other metal parts? Does it hum when you use a different cable connected to the amp? Do you hear the same hum from the amplifier (even if it's much quieter) when you unplug the guitar from the amp? Do you hear any crackles or other intermittent electrical noises from the amp when you turn the pots, wiggle the cable plug in the guitar jack, tap on the pot knobs, or shake the guitar while it's plugged in?

Your guitar is not typical of the shorter scale / 3/4 body size models of the day. It's a very nice guitar that's made as well as any other Guild and is the equal of its bigger brother apart from its size. I'm pretty sure Keith Richards either played or endorsed a double pickup M65 at some point in the mid '60s. I've seen asking prices of $1k+ for the small ones, so they're not dead in the water for value either. It's well worth taking good care of it and making right.

[stevo58]

Pots don’t cause hum, normally. The single coil pickup can cause hum; a grounding problem in the guitar or cord or amp can cause hum.

Does the hum change when you change the distance to the amp, or the angle? Did you test it in a room with fluorescent lights, or near the kitchen?

[JWMandy]

Thanks guys. Hums anywhere, anytime, any amp, any cable. Had it checked out, and the tech simply said he didn't want to mess with a collector's guitar. Problem's acknowledged as there, and he was more familiar with the M-75 full size version. He suggested previous owner might not have played it in a long time and that can have an impact on the pots... and active use might have some role. Nice to be told, play with the knobs, play the guitar, etc.

But the problem's still there and a collector's item it ain't... at least not really. Maybe a budget collector.And it is nice and in nice shape, but to me, it's a guitar. I'd love less hum. Guy didn't charge anything - despite my offer as reasonable comp for his time. Knows his stuff? Yes I think so. Certainly knows his instruments and play gigs quite a lot.... less since Covid though. Might check another tech.... but thought to start here. Yes it's a Franz pickup I think.

[nevershouldhavesoldit]

Yes it's a Franz pickup I think.

As I recall, Curtis Novak is the resident US authority on Franz pickups. If you reach out to him, he might have some helpful info for you about common causes of noise. But if you can get inside with a mirror or bore scope of some kind, you should look at the wiring to see if you can find a broken or suspect wire or joint. Solder joints should be clean and shiny looking. If one is mottled or even broken, you can probably see it. Look closely at the pots where the ground wires are soldered to the cases, since that's often where you'll find a broken joint.

Look for a single wire that runs from a hole in the end of the body side near the endpin to any ground point. Common sites of a broken string / tailpieve ground connection are the metal backs of the pots and the ground lug on the output jack.

[sgosnell]

Pots are just variable resistors, and don't usually cause hum. I would first investigate grounding. There needs to be a common ground from the pickup, to each pot, and to the output jack. An ohmmeter should show continuity between the case of the pickup and the outer portion of the output jack, and to the strings. If you don't get that, you have a grounding problem. That should be checked before even thinking about changing out any parts. My first guess would be lack of a string ground, but a loose ground wire anywhere is possible.

[nevershouldhavesoldit]

My first guess would be lack of a string ground

That's certainly one possibility. But if the string ground is open and everything else is OK, the hum usually gets much quieter or goes away when you touch the strings or the tailpiece. That's why I asked in my first response "Does it change or go away when you touch the strings or any other metal parts? "

As the pots are said by the OP to have 1975 date codes and this model does not appear in the Guild catalogs I have after 1968, the pots are probably not original. If so, a ground connection to the back of a pot is the most suspect. A good solder joint between a bare wire and a flat metal surface requires that the case be heated enough to melt the solder.

Many inexpert solderers just heat the solder itself until it drips onto a joint. This is the commonest cause of failure of such joints, because there’s no mechanical retention (like you get by twisting wire ends together before soldering them). And without solid support, the wire can move a little as the solder solidifies. This combination can cause microcracking in the solder, with loosening of contact and finite electrical resistance (a “cold” joint), when there should be none.

[whiskey02]

You are free to do anything you want to your property. My only thought is, if it is "collectable" and you're not thrilled with it as it now is, perhaps get a reliable price estimate for it. If it's worth more than you think, you could sell it and get something that fits your needs better with the funds. But. ultimately it's yours and if you want to put a whammy bar and paint it purple,; ain't nobody's business.

[JWMandy]

Guys: Thanks! These are good ideas. Don't think my tech did that sort of thing. More a general set-up check out. So I'll look further. Thanks! Very VERY helpful to a newby.

[SOLR]

Guys: Thanks! These are good ideas. Don't think my tech did that sort of thing. More a general set-up check out. So I'll look further. Thanks! Very VERY helpful to a newby.

As others have stated it's a single coil which might bring it's own set of issues.

But to illustrate what never.....posted .......here's a short YT

You can pretty much do this yourself if you have a multimeter...

And finally have you tried a hum eliminator pedal? these are really inexpensive and sometimes get rid of the issue and let you play without affecting the value....does your hum match this one:

S