Odd bridge intonation discrepancy

[JimmyM]

Replaced the bridge on my 09 AmStd Precision with a Hipshot A last night. I swapped them because I switched string brands from D'addario XL's to Dunlop Super Bright Nickels, and the D string required the saddle to be pushed so far up the bridge that it ran out of track for the saddle screws.

So I put the new bridge on, used the same strings and strung it up thru-body as I did my old bridge, set it up with the same action, and got quite a surprise (pardon the bad photography):

While the E, A and G saddles are in relatively the same spots as before, the D string intonates much further back than it did with the Fender bridge. The saddles on the Hipshot actually form your usual diagonal line, but the D on the Fender bridge is crazy out of whack with the others. This was the only way I could get the D to intonate with the Fender bridge and the Dunlops. Didn't do it with the XL's, but does it bigtime with the Dunlops.

So my question is what could possibly have been causing the D string to intonate so weirdly with the Fender bridge but normalize with the Hipshot?

 

[202dy]

Burr in the saddle.
Bend in the string.
False string.

First three places to investigate.

 

[JimmyM]

Bend in the string sounds possible although I did try one top loaded with the Fender bridge, and it had no bends but intonated in the same spot. False string is out, though...the same string intonates perfectly with the Hipshot and sounds normal as well.

 

[202dy]

If there is no burr in the saddle check to make sure that the bottom of the of the seat is flat and angled toward the tailpiece. In this case, the tailpiece is integrated with the bridge. If it is not angled then the string must leave the rear of the seat cleanly toward the anchor point and have no hump in the seat. If none of these are a problem then it is the string.

 

[JimmyM]

If there is no burr in the saddle check to make sure that the bottom of the of the seat is flat and angled toward the tailpiece. In this case, the tailpiece is integrated with the bridge. If it is not angled then the string must leave the rear of the seat cleanly toward the anchor point and have no hump in the seat. If none of these are a problem then it is the string.

I just checked for burrs and nothing jumps out at me. Maybe it was the way the string had to roll around the saddle as compared to the Hipshot, which has a much smaller saddle with no rolling required. I could be wrong, but I really don't think the string is the culprit here, as I rotate like 4 sets of strings in an alcohol bath to keep them sounding new, and they all intonated similarly with the Fender bridge. Could be wrong, though, since the D string was the only one that does it. Sounds fine, though. I've had false strings before and they're impossible to intonate and have odd overtones. So I think the likely culprit is the string not coming off the back of the saddle flat.

Thx for the advice, bro. I think you're onto something with that.

 

[Jay2U]

The only thing I can imagine, is a bridge which didn't have full contact with the body, underneath the D string. A system of D string and partial 'floating', resonating bridge may have existed. Rare, but I can't come up with anything more credible.

 

[walterw]

the plot thickens!

it might be worth measuring with a yardstick or tape measure the exact length of that D from fret-side edge of nut to saddle contact point. (in the interests of internet science, you should then put the fender bridge back on and make the same measurements after intonating )

theoretically, at no time should any of the strings end up shorter than the nominal scale length of 34".

you are doing the "witness point" thing of pushing out any string curving up off the nut and saddle, right?

 

[JimmyM]

the plot thickens!

it might be worth measuring with a yardstick or tape measure the exact length of that D from fret-side edge of nut to saddle contact point. (in the interests of internet science, you should then put the fender bridge back on and make the same measurements after intonating )

theoretically, at no time should any of the strings end up shorter than the nominal scale length of 34".

you are doing the "witness point" thing of pushing out any string curving up off the nut and saddle, right?

I have in the past I didn't with those strings last night, but yeah, I've done the witness point thing before and it didn't seem to make a difference with intonation. Did cure rattles I've had in the past, though.

You know, if it wasn't so much work, I'd probably try that measuring. Should have thought to do that beforehand, but who knew this would happen?