Help! 60-cycle hum on MM Stingray 5

[Homer Simpson]

Hello,
I have Music Man Stingray 5 '98 (ceramic PU and fantom coil). I love this bass, it plays great. But I am very worried about the noise issue. There is 60 cycle hum in parallel mode, but serial mode and single mode are absolutely quiet.
I did a lot to fix this:
1. Connected bass to different amplifiers on different stages;
2. Tried connecting bass with different cables;
3. Inserted several brand new batteries;
4. Checked the soldering on the preamp and pickup, checked the wiring diagram;
5. My bass was shielding with copper foil;
6. Installed a new battery compartment;
7. Installed a new 3-way switch;
8. Installed a new output jack;
9. I also corresponded with EBMM customer support, got a new original pickup and installed it. I checked the new pickup.
BUT ... the 60 cycle hum is still there.
It drives me crazy!)
The EBMM customer support guys didn't find any reason for the 60 cycle hum. They wrote to me about the possibility to put a original newer preamp. Then I would have to install an alnico pickup and pickguard as well, since my preamp version is no longer in production. But I would not want to install an alnico pickup and a newer preamp.
I cannot send my bass to EBMM customer support because I live in Ukraine. Sorry for my English.
So, has anyone had such a problem? Any idea what it could be?

 

[tbonesullivan]

If you have hum, I would assume that the second coil is not connecting correctly in parallel mode.

 

[nhbassguitar]

здравствуйте (zdrass-VOOY-tay). Your English is almost perfect. No need to apologize.

Interesting problem.

1) Was this bass guitar bought used, previously owned?

2) If so, did you wire the new switch the same way as the old one?

If "yes" to both questions, then is it possible one of the short jumper wires on the old switch was missing or in the wrong location?

I tried to find the correct switch wiring on the Internet but was unsuccessful.

 

[Homer Simpson]

Interesting problem.

1) Was this bass guitar bought used, previously owned?

2) If so, did you wire the new switch the same way as the old one?

Thanks for getting back to me!
1) Yes, I bought my bass used.
2) No, I connected a new switch according to the wiring diagram.
I must say that the old and new switches are wired in the same way.

 

[Homer Simpson]

If you have hum, I would assume that the second coil is not connecting correctly in parallel mode.

I thought about it too. Therefore, I checked the wiring diagram several times

 

[nhbassguitar]

When you received the new switch, were the short jumpers already in place, or did you add them yourself?

Can you post here (or link to) the wiring diagram you used? I still haven't found one that shows the jumpers on the switch (if there are any at all).

If parallel mode is noisy, that means one or both of the following:

1) The coils are being connected IN phase by the switch, rather than out of phase. That would mean one coil's wires are reversed at the switch, or a jumper wire is in the wrong place or not present.

2) The phantom coil is being connected, and it shouldn't be, since the two pickup coils are (or should be) connected out of phase by the switch, and that's what cancels the hum. Adding that extra coil to a configuration that's already humbucking might pick up hum.

This is why it would be helpful to see the switch wiring instructions and diagram from EBMM.

There's also the slight possibility you have a wire whose insulation is worn or burned away and the wire is contacting ground somewhere (either the cavity shielding or the back of one of the potentiometers). But the probability of that is low, since you have hum in only one switch position, not all positions.

DISCLAIMER: I'm a tech (guitar/bass/electronics) and amp builder but I've never worked on Stingray electronics, so please take that into consideration. I have ZERO hands-on experience when it comes to this topic. I'm just "thinking out loud" as the saying goes, based on the little I know from available diagrams.

 

[tbonesullivan]

I thought about it too. Therefore, I checked the wiring diagram several times

I do remember that part of the wiring is built into the preamp, so maybe something went or developed a cold solder joint.

 

[Homer Simpson]

When you received the new switch, were the short jumpers already in place, or did you add them yourself?

Can you post here (or link to) the wiring diagram you used? I still haven't found one that shows the jumpers on the switch (if there are any at all).

I just unsoldered the wires from the old switch and soldered them to the new switch.
When installing a new switch, I used this diagram

 

[nhbassguitar]

Well, now I'm really confused.

The SR5 (single H) added a phantom coil late 1992 / early 1993. But the diagram you posted is dated 1996, years after the extra coil was added. That date makes no sense because the only wires I see coming into the preamp are the 2 wires for each coil, plus shield, for a total of 5. I don't see any connection to a phantom coil. That suggests the diagram is for earlier SR5 models, the ones without the phantom coil.

-- OR --

The phantom coil connection is made somewhere off the board, so it doesn't show up on the diagram.

-- OR --

I'm going crazy, blind, or both.

As an experiment, try wiring your SR5 exactly as shown on the diagram, and don't connect the phantom coil to anything. Just leave the wires hanging. You should get a quiet signal in series and parallel, and some hum in single-coil mode.

 

[nhbassguitar]

For Homer: If you've not done so already, get out your ohmmeter and check for continuity among all the ground points. Also make sure the control cavity plate is making good contact with the cavity shielding. Take the battery out first, just to be safe.

Something else you can check: If the phantom coil wires can be disconnected from where they're soldered, unsolder them and then check the phantom coil's resistance with your ohmmeter. If you get a very low (or zero) reading, or if you get a ridiculously high (or infinite) reading, there's your problem.

 

[Bert]

Pic of dummy coil:

 

[nhbassguitar]

Thanks, Bert. Very helpful.

Homer, don't unsolder those wires if you have a piggybacked coil like Bert shows.

Anyway, looks like they've got the phantom coil in series with one pickup winding.

I don't know where to go at this point. Homer, may I ask you, when the bass guitar is plugged in and in parallel mode, you get the hum, yes? Now, does the hum change volume as you turn from side to side, and move around the room?

 

[Homer Simpson]

Thanks, Bert. Very helpful.

Homer, don't unsolder those wires if you have a piggybacked coil like Bert shows.

Anyway, looks like they've got the phantom coil in series with one pickup winding.

I don't know where to go at this point. Homer, may I ask you, when the bass guitar is plugged in and in parallel mode, you get the hum, yes? Now, does the hum change volume as you turn from side to side, and move around the room?

Yes you are right. The noise changes as I move around the room. I live in an old house.

 

[nhbassguitar]

Homer: Are your electrical outlets properly grounded? I mean, are there 3 wires feeding them (separate earth ground wire connected to the earth ground buss bar in the main panel), AND is that buss bar connected to an external grounding (earthing) rod sunk into the dirt somewhere close to the house? You will have to visually inspect the outlet wiring and the inside of the main panel and find the grounding rod to get these answers. Be careful. Ukraine is 220 volts and it will kill you if you make a mistake. You may wish to pay for 1 hour of an electrician's time to do a site assessment for you, just to be on the safe side.

Still, even if the power is the source of the noise (and it seems like it is from what you say), I’m still confused why parallel mode is the noisy setting. So, let me ask you: Forget the noise for the moment, and please tell me whether the instrument’s tone is ok in parallel mode. It should sound well-balanced top to bottom. In comparison, series mode should sound fuller and more “muscular,” especially at the bottom end, while the single-coil setting should sound thin (no bottom end, all treble), like a Fender Jazz Bass with only the bridge pickup in use (for example, Jaco Pastorius’s or Joe Dart’s tone).

 

[Homer Simpson]

Homer: Are your electrical outlets properly grounded?

You are right, I live in an old house and the electrical outlets are not grounded. But 60 cycles of hum is present, even in places with proper grounding.

So, let me ask you: Forget the noise for the moment, and please tell me whether the instrument’s tone is ok in parallel mode. It should sound well-balanced top to bottom. In comparison, series mode should sound fuller and more “muscular,” especially at the bottom end, while the single-coil setting should sound thin (no bottom end, all treble), like a Fender Jazz Bass with only the bridge pickup in use (for example, Jaco Pastorius’s or Joe Dart’s tone).

My bass sounds like you described it. I'll check everything very carefully tonight, following your advice.
I am very grateful to you!

 

[Homer Simpson]

So today I once again сhecked the soldering on the preamp and pickup. And I finally found the reason for the hum! the soldering on short jumpers was broken. It was hard to see.

Now I am extremely happy!
I am grateful to everyone who expressed their thoughts and gave advice!
Here is my baby:

 

[Bert]

 

[nhbassguitar]

Спасибо for letting us know what the problem was.

 

[tbonesullivan]

Great to hear! Yeah those tiny solder joints can be so hard to see. They look great from most angles, and unless you get the right one, you never see it.