Ground hum? Think I found it, need some help - Ibanez EBH1005MS

[Sklrtle]

I recently got an Invalid Link Removed, I've noticed it has what sounds like a ground hum. I've tried two different power supplies, running my bass DI, and using headphone amps. So I feel I've effectively narrowed down the bass.

The hum remains if I touch the strings, or any of the metal.

I started poking around with my multimeter, and I found that I get continuity through every thing except the highlighted connectors below. Testing one end of the wire to the other works fine, but when I touch the exposed pins on the back side of the connector I get a very brief reading on the red and black pins, and a -1 on the white one.
I'm guessing this is the issue, but I'm not exactly sure what to do about it. Could I just jumper the pins to a ground?

I made a wiring diagram to help. Here's the one with the highlights.

And without the highlights, should anyone else need it in the future.

 

[dwizum]

Hum present in both active and passive modes?

Do you have an actual schematic of the circuit? It's hard to know what sort of multimeter reading to get on any certain part or how to fix it (i.e. your suggestion of jumpering to ground) without knowing how the circuit is supposed to work.

 

[Kinkh]

...

I started poking around with my multimeter, and I found that I get continuity through every thing except the highlighted connectors below. Testing one end of the wire to the other works fine, but when I touch the exposed pins on the back side of the connector I get a very brief reading on the red and black pins, and a -1 on the white one.
I'm guessing this is the issue, but I'm not exactly sure what to do about it. Could I just jumper the pins to a ground?

Can you elaborate this part a bit more: what do you mean black and red pins? As in the pins that go to red and black wires?

Jumpering to ground may or may not work, depends where the connection is supposed to go - which is a bit hard to know without a schematic or something.

Also, pictures of the electronics you measured would also help i suppose.

May not be the issue here, but worth mentioning - how is your ground wiring in the house (place where you palyed or noticed the hum)? Could be a faulty ground installation.

 

[Sklrtle]

Hum present in both active and passive modes?

Do you have an actual schematic of the circuit? It's hard to know what sort of multimeter reading to get on any certain part or how to fix it (i.e. your suggestion of jumpering to ground) without knowing how the circuit is supposed to work.

It is present in both, but it disappears in active if you take out the battery.

Unfortunately no, I couldn't find one. I could possibly spend some time and more or less make one, but I suspect that would take me a while.

 

[Sklrtle]

Can you elaborate this part a bit more: what do you mean black and red pins? As in the pins that go to red and black wires?

Jumpering to ground may or may not work, depends where the connection is supposed to go - which is a bit hard to know without a schematic or something.

Also, pictures of the electronics you measured would also help i suppose.

May not be the issue here, but worth mentioning - how is your ground wiring in the house (place where you palyed or noticed the hum)? Could be a faulty ground installation.

Yeah the pins to that go to those wires.

It's kind of a rats nest in there, but I took some pictures. I'll put them at the bottom of this reply.

The wiring in my house does suck, but, the issue was present in a battery powered headphone amp as well. One of my other basses doesn't have this problem with that same headphone amp.

3EMP3LD

3EMV5-S - Volume

Pickup Blend

Active/Passive Switch

3EMMV84-C - Bass, Treble/Tone

3EMB410B-CB - Mid/Mid frequency - These were harder to get, so here are my best attempts

 

[dwizum]

What about playing it at someone else's house, or a gig venue? When you tried the headphone amp, were you using the same cable?

It's really hard to advise on things like "jumper this pin to ground because you didn't get a multimeter reading on it" without seeing a schematic. Doing so could kill the preamp or cause unintended problems. I certainly wouldn't expect every single pin on a cable between preamp components to have continuity to ground.

You mentioned the hum stays if you touch the strings. Does it change at all? Can you check the bridge ground (use your multimeter to take a resistance reading between the strings and the ground lug on the jack)?

 

[Sklrtle]

What about playing it at someone else's house, or a gig venue? When you tried the headphone amp, were you using the same cable?

It's really hard to advise on things like "jumper this pin to ground because you didn't get a multimeter reading on it" without seeing a schematic. Doing so could kill the preamp or cause unintended problems. I certainly wouldn't expect every single pin on a cable between preamp components to have continuity to ground.

You mentioned the hum stays if you touch the strings. Does it change at all? Can you check the bridge ground (use your multimeter to take a resistance reading between the strings and the ground lug on the jack)?

Different cable with the headphone amp, I can try plugging in downstairs where the wiring is better. However, I did test out my SDGR and didn't have any problems with a hum. I thought I had mentioned that already, my bad.

Edit: Forgot to reply to the rest

Nothing changes when I touch any of the metal, strings included. The resistance reading between the strings was pretty low. With the multimeter set to 200 ohms I got a reading of about 40 on the B string and about 5 on the G

 

[dwizum]

Using plain old normal 9v batteries? There was a thread earlier this month where someone was using rechargeable that had an active circuit in it which caused interference noise.

Does the noise change at all between active and passive modes? Or is it exactly the same?

Can you trace the wiring for the active/passive switch and determine how it functions? Some active/passive switches cut the preamp completely out, others don't. Might help narrow it down to the preamp vs the pickups (or something else.)

 

[Sklrtle]

Using plain old normal 9v batteries? There was a thread earlier this month where someone was using rechargeable that had an active circuit in it which caused interference noise.

Does the noise change at all between active and passive modes? Or is it exactly the same?

Can you trace the wiring for the active/passive switch and determine how it functions? Some active/passive switches cut the preamp completely out, others don't. Might help narrow it down to the preamp vs the pickups (or something else.)

Yeah, it's just a regular 9V. Maybe I'll try swapping for the 9V in my SDGR just for ***** and giggles.

Its pretty similar between active and passive. It does change when I twist the tone/treble knob though. None of the other knobs seem to have an effect, other than the volume.
I'll see what I can do so far as tracing the wiring for the switch, in the mean time, I snapped a photo of the other side of the preamp.

Thanks for taking the time to help me troubleshoot, by the way.

 

[dwizum]

Interference like this going away when you drop the treble control is pretty normal, it's just a sign that your treble control is working (the noise is higher in frequency and you're cutting high frequencies).

The photo of your active/passive switch looks like it's likely cutting the preamp out since all six terminals appear used - it's likely that one set of terminals is switching each side (input and output) of the preamp.

I'd be tempted to bypass the controls entirely and see what happens if you hard wire one pickup directly to the jack (nothing else connected to the jack). Then you could narrow down a little bit if the sound is coming from the pickups (likely them picking up some kind of interference) or the preamp (could be just a bad design, interference, a fault, or something else). Some preamps are really prone to noise like this, sometimes drastic steps can help, like putting a permanent low pass filter in front of the preamp. Of course, that will change your tone, but that's not always inherently a bad thing.

 

[Sklrtle]

Maybe I'll give it a try, I have to re-attach the bare wire on my neck pick up anyways, it broke off while I was trying to make that wiring diagram.
I tested again after, with an alligator clip to the bare wire and touching it back to the ground point, but the hum stayed, so I'm pretty sure the hum wasn't from it being lose.

 

[Kinkh]

Ok, so in addition to everything @dwizum said, I'll just add the things about the jumpering and physical connections you mentioned.
That big copper surface is GND. I have circled two pins that I can see from the picture (double check just to be sure) that have a connection to GND.
Now with all connectors unplugged, check continuity between one of these points you are 100% sure is GND and the problematic pin. That way you will see if any of the problematic pins is connected to GND.

However, as you can't see the tracks on the other side of the PCB due to the connector housing, you won't be able to tell if the pin is connected to GND or not just by visually looking. So if it's broken on the other side, you may not get any continuity to GND even if it should be there.

In case of bad solder joints (those can happen after time when lead-free solder is used), you could try heating the problematic pins and adding a small amount of solder to each.

Those are just some general tips to help you troubleshoot. And to let you know can you safely jumper to ground or not.
Also, you could try testing continuity directly from the solder points on both pcbs. If the cable itself is ok as you sad, this will give you an indication if the connector housing / or PCB solder point is the issue.

Moving on to your other photos, on this photo the wire connection seems a bit dodgy:

So it might be worth looking into it.

That's all I can think of for now. If I remember anything all add the info.

 

[Kinkh]

Also, as for the in house wiring: I have sh*t installations, actually no ground wire in the whole house.
Out of six instruments tested (some passive, some active), 5 have hum issues similar to you, and one active instrument is clean without any noise or hum. All played on the same amp in the same room.

 

[Sklrtle]

Ok, so in addition to everything @dwizum said, I'll just add the things about the jumpering and physical connections you mentioned.
That big copper surface is GND. I have circled two pins that I can see from the picture (double check just to be sure) that have a connection to GND.
Now with all connectors unplugged, check continuity between one of these points you are 100% sure is GND and the problematic pin. That way you will see if any of the problematic pins is connected to GND.

However, as you can't see the tracks on the other side of the PCB due to the connector housing, you won't be able to tell if the pin is connected to GND or not just by visually looking. So if it's broken on the other side, you may not get any continuity to GND even if it should be there.

In case of bad solder joints (those can happen after time when lead-free solder is used), you could try heating the problematic pins and adding a small amount of solder to each.

So I got a little tricky with it, and used a bright backlight to take a look at the tracing. As it turns out, I think none of those points go to ground. You can see on the pins that do go to ground little, connectors for lack of a better word, going to the joint.
So there goes that theory of mine, haha.

While I have the soldering iron out, I'll have to touch up that joint on the switch you were pointing out. I almost wonder if I should just re-do all of it, there is a handful of joints that seem iffy tbh.

 

[Kinkh]

Excellent idea! Well good thing you didn't solder anything to ground before checking

No harm in retouching any joints that seem suspicious. Especially all the ones you know go to ground - on the pcb, pots, switches everywhere. Because even a tiny loose connection to ground can lead to problems.

 

[themickster]

3EMP3LD View attachment 4482787

One of the connectors on pic 3EMP3LD doesn't look all the way in. Could that be the problem?

 

[Sid the Kid]

My EHB had a terrible hum as well. Exact same as you describe. In my case the bridge ground was actually severed by the bridge pickup being set too low. For your sanity check the integrity of the bridge ground wire before chasing anything else.

 

[OldSchoolFlats]

Do you have fluorescent lights? Some basses don't like 'em. Ditto with dimmers on lights.

 

[Sklrtle]

One of the connectors on pic 3EMP3LD doesn't look all the way in. Could that be the problem?

Maybe, admittedly I didn't try pushing it back in. Everything is a part at the moment, once I get some new copper tape tomorrow, I'm going to put some shielding in and put everything back together.
The joints from the pickups to the PCB for the blend were pretty weak, I'm wondering if maybe that was the cause.

 

[Sklrtle]

My EHB had a terrible hum as well. Exact same as you describe. In my case the bridge ground was actually severed by the bridge pickup being set too low. For your sanity check the integrity of the bridge ground wire before chasing anything else.

I'll double check it, but when I ran it last I was getting continuity at least from everywhere on the bridge. I don't remember what the numbers were though.