Experiencing hum after installing Novak JM90 bridge

[mn3005]

Hi all,

Long time lurker, first time poster. I have an awesome Chicago Music Exchange exclusive Sherwood Green American Original that I decided needed a Novak JM90 in it. While I was in there, I replaced the volume and tone pots as well.

When I was all done, the pickups sounded out of phase so I went back in and switched the leads on the bridge. The middle position then sounded better, but now there is a hum that is on all three positions: neck, bridge, AND middle. It’s perhaps even worst in the middle position...

When I touch metal, the hum does NOT go away. Does that mean I have a grounding issue? Any other ideas? Was switching the leads not the right thing to do? Help!

[timtam]

Hi all,

Long time lurker, first time poster. I have an awesome Chicago Music Exchange exclusive Sherwood Green American Original that I decided needed a Novak JM90 in it. While I was in there, I replaced the volume and tone pots as well.

When I was all done, the pickups sounded out of phase so I went back in and switched the leads on the bridge. The middle position then sounded better, but now there is a hum that is on all three positions: neck, bridge, AND middle. It’s perhaps even worst in the middle position...

When I touch metal, the hum does NOT go away. Does that mean I have a grounding issue? Any other ideas? Was switching the leads not the right thing to do? Help!

Possibly several things going in here. Resolve the obvious one first. Do you have multimeter ? Sounds like your metal may not be grounded (noise should reduce when touching grounded metal as you are then grounding your human noise antenna). Test for continuity (~zero ohms) between rim of output jack and bridge, trem, strings.

If you still have noise when touching metal despite OK ground connection, then something else is going on. If no metal-ground continuity, it's also worth testing output socket tip to metal, in case you've tied hot to what should be ground somewhere.

Next issue (probably unrelated to first ?) is that while the Novak is no longer out of phase with the stock pickup it may also no longer be hum cancelling in the middle position (which should normally be quieter), which is a result of the particular combination of both pickups' winding direction and magnet polarity ..
https://www.premierguitar.com/articles/ ... e-with-you
"When you want to combine pickups, there are four golden rules regarding winding direction and polarity:
Rule 1. Opposite winding direction + opposite polarity = in phase with hum cancelling.
Rule 2. Identical winding direction + identical polarity = in phase, no hum cancelling.
Rule 3. Identical winding direction + opposite polarity = out of phase, no hum cancelling.
Rule 4. Opposite winding direction + identical polarity = out of phase, no hum cancelling."

The pickups are JM-90 and stock neck, right ? And the JM-90 was bought as a 'bridge' pickup ? (which may be how he determines which polarity/winding direction to supply ... ideally both are opposite for neck vs bridge).

Anyway see what the outcome of the ground investigations are first.

[mn3005]

This is a picture of the jm90. Are those magnets my problem? Reversing my polarity??

[mn3005]

Hi all,

Long time lurker, first time poster. I have an awesome Chicago Music Exchange exclusive Sherwood Green American Original that I decided needed a Novak JM90 in it. While I was in there, I replaced the volume and tone pots as well.

When I was all done, the pickups sounded out of phase so I went back in and switched the leads on the bridge. The middle position then sounded better, but now there is a hum that is on all three positions: neck, bridge, AND middle. It’s perhaps even worst in the middle position...

When I touch metal, the hum does NOT go away. Does that mean I have a grounding issue? Any other ideas? Was switching the leads not the right thing to do? Help!

Possibly several things going in here. Resolve the obvious one first. Do you have multimeter ? Sounds like your metal may not be grounded (noise should reduce when touching grounded metal as you are then grounding your human noise antenna). Test for continuity (~zero ohms) between rim of output jack and bridge, trem, strings.

If you still have noise when touching metal despite OK ground connection, then something else is going on. If no metal-ground continuity, it's also worth testing output socket tip to metal, in case you've tied hot to what should be ground somewhere.

Next issue (probably unrelated to first ?) is that while the Novak is no longer out of phase with the stock pickup it may also no longer be hum cancelling in the middle position (which should normally be quieter), which is a result of the particular combination of both pickups' winding direction and magnet polarity ..
https://www.premierguitar.com/articles/ ... e-with-you
"When you want to combine pickups, there are four golden rules regarding winding direction and polarity:
Rule 1. Opposite winding direction + opposite polarity = in phase with hum cancelling.
Rule 2. Identical winding direction + identical polarity = in phase, no hum cancelling.
Rule 3. Identical winding direction + opposite polarity = out of phase, no hum cancelling.
Rule 4. Opposite winding direction + identical polarity = out of phase, no hum cancelling."

The pickups are JM-90 and stock neck, right ? And the JM-90 was bought as a 'bridge' pickup ? (which may be how he determines which polarity/winding direction to supply ... ideally both are opposite for neck vs bridge).

Anyway see what the outcome of the ground investigations are first.

super helpful! thank you.

yes, the neck is a stock AV65 pickup.

[mn3005]

I asked Curtis this question via email and he responded:

“Oh right on.. yes it might now be in phase but not hum canceled now. You might want to put the old bridge pickup in the heck. It does also sound like a ground problem “

I checked all my grounds per your suggestion, timtam and they seem fine. I went ahead and put in the bridge pup and low and behold it’s hum cancelling and also in phase! Relates to the second half of your answer, timtam, as I understand it.

Now my question is: how different are the AV65 neck and bridge pups? Are they really interchangeable like that sound wise?

[Embenny]

There is no difference in specification between neck and bridge pickup other than winding direction and magnet polarity. The concept of overwound bridge pickups being necessary or standard is a relatively modern one. Vintage pickups and reissues don't "calibrate" (overwind) the bridge.

[mn3005]

There is no difference in specification between neck and bridge pickup other than winding direction and magnet polarity. The concept of overwound bridge pickups being necessary or standard is a relatively modern one. Vintage pickups and reissues don't "calibrate" (overwind) the bridge.

makes sense! thanks for the reply. cheers

[Fiddy]

Battle of the quotes

[mn3005]

Battle of the quotes

had to.