CE intonation shift

[musicroom]

I’ve removed and re-fitted a few old Mann trems on 80s guitars that arrived incorrectly set up.

Looking at your pics I don’t think your screws are set properly / equally for height – the G screw looks high to me.

When I set PRS trems from scratch I use a hex wrench as a guide but also check VERY carefully that the screw slots align and that the trem block knife edge is siting in the screw grooves. I'd check initially by eye looking at the grooves to be sure they were all in alignment.

To additionaly check it’s set properly I remove all the strings and the springs and rock / pivot the block by pushing it on to the screws to make sure the screw grooves are all sitting at the right height / in the knife edge and that the trem pivots freely. I also check the trem base is parallel both front and rear to the guitar body and not tipped up or down at one side.

If one or more screw is not sitting correctly the knife edge will set on the screw body not in the groove, potentially making the trem out of alignment, which will throw up this sort of intonation issue.

Other things I can think of are one or more pivot screws are bent – I have had this. On the early guitars they’re brass, so can bend. If a screw is bent then the trem can set incorrectly – the screw will whirl for want of a better description, changing its position at any given amount of screw rotation.

Another thing I would try to check is that the trem is set square to the frets. I would do this by taking a picture of the trem and the frets and - using the frets as a datum - check the front edge and trem pivot screws all look to be parallel to the frets. The guitar where one of the pivot screws was bent failed this test – the trem block sat out of square.

The only other thing I can think of is that the nut has moved or become loose.

Thank you for the well thought out post! I will check each point you made to verify proper bridge alignment. Can you just stop by the house and straighten this issue out for me? LOL Thanks again!

 

[Collywobbles]

Thank you for the well thought out post! I will check each point you made to verify proper bridge alignment. Can you just stop by the house and straighten this issue out for me? LOL Thanks again!

That will (hopefully) give you a nicely set trem, which is a good place to start from.

However, looking at the pictures your saddles are such a long way out that I think it must be something else as well, even if the trem is out.

To explain what intonation is and why your saddles look so wrong - it's a compensation for the increase in string tension from pusing the string down to fret it, because fretting stretches the string slightly. The thicker the string the more the tension increases, hence the string stagger for strings of different guages. For wrapped strings it's the core of the string that matters - hence wrapped strings have their own stagger.

As your saddles are so far out in the pictures I would re-set the saddles to the nominal scale length and start again.

A good starting point is measure the distance from the nut edge to the 12th fret and then meaure the same from the 12th fret to the bridge - this should give a decent staring point for setting the saddles.

Other thoughts

I'd possibly use a different brand of string in case it's a manufacturing error.

I'd check you're using a decent tuner and that the tuner battery wasn't going flat

Also that the neck screws are tight and the nut is OK.

Other things I can also think

String wrap on the ball end - some brand's string-ball wrapping is so long it encroaches on the saddle / string take off point - so check that. I tend to use Ernie Ball and their strings are like this so I normally thread an old string ball onto the string so it pulls the wrap away from the saddles. PRS trem blocks have a fairly deep drilling to minimise dead string length - hence this can be an issue. (Hopefully that makes sense).

Action and relief need to be roughly factory (or at least not miles out) - so check them. I use a notched straight edge and feeler guages for relief and a StewMac steel ruler for action. I also use under-saddle string radius guages so the strings are set to the board radius.

Also the trems were originally designed around the 9-42 strings shipped with guitars back in the day. If you're using some monster guage strings this might be the cause of the issue.

I have nothing more to say Good luck!

 

[gush]

Not sure about your intonation issue but your fulcrum screws appear to be uneven.

I'd definitely correct that if you know how.

 

[gush]

Also, the saddle screws on D string have left marks on trem. It looks like you adjusted that saddle with tension on it?

I would definitely check neck relief as that's the only thing I can think of that would cause a drastic and immediate intonation change unless of course it's been dropped or hit.

 

[John Mann]

Check this troubleshooting guide out - https://www.johnmannsguitarvault.com/faq---frequently-asked-questions.htm

uning Stability Troubleshooting Guide​

My guitar will not stay in tune. What's wrong? Troubleshooting tuning issues: 1. Is bridge installed correctly? a. Watch video - b. Saddle height should match fingerboard radius. c. Saddles should be parallel to the bridge plate. Both height set screws should be the same height, NOT angled! 2. Is nut installed correctly? a. Strings should pass thru the nut in a straight line. b. Strings should not bind, pinch or stick in the string slot. c. Do you hear “pinging” when tuning up to pitch? That is a clear sign that the string in pinched in the string slot. d. If guitar is equipped with a vibrato (tremolo) bridge, the nut should be made of a material that self- lubricates. 3. Are tuners installed correctly? a. Tuners should be mounted securely, with no looseness (free play or wiggle). b. Are strings relatively new? “Dead” strings tend not to hold their tuning. c. Always tune up to pitch (not down). The tuning gear must have pressure on the gears to hold tuning properly. d. Are the strings properly wound on the tuner peg? The string should self-lock on itself to eliminate any slippage. How to do it - http://www.prsguitars.com/csc/tuners.html e. If guitar is equipped with a vibrato (tremolo) bridge, locking tuners are a must. 4. Are frets dressed and level? a. Excessive fret wear will cause a note to play out of tune. 5. Is truss rod properly adjusted? 6. Is guitar properly intonated? 7. Are pickups set too close to the strings? a. Pickups that are set too close to the strings will cause the guitar to go out of tune, due to the magnetic pull of the pickup magnets.

 

[Broseph]

The authority of the OG PRS tremolo bridge has spoken

 

[musicroom]

Check this troubleshooting guide out - https://www.johnmannsguitarvault.com/faq---frequently-asked-questions.htm

uning Stability Troubleshooting Guide​

My guitar will not stay in tune. What's wrong? Troubleshooting tuning issues: 1. Is bridge installed correctly? a. Watch video - b. Saddle height should match fingerboard radius. c. Saddles should be parallel to the bridge plate. Both height set screws should be the same height, NOT angled! 2. Is nut installed correctly? a. Strings should pass thru the nut in a straight line. b. Strings should not bind, pinch or stick in the string slot. c. Do you hear “pinging” when tuning up to pitch? That is a clear sign that the string in pinched in the string slot. d. If guitar is equipped with a vibrato (tremolo) bridge, the nut should be made of a material that self- lubricates. 3. Are tuners installed correctly? a. Tuners should be mounted securely, with no looseness (free play or wiggle). b. Are strings relatively new? “Dead” strings tend not to hold their tuning. c. Always tune up to pitch (not down). The tuning gear must have pressure on the gears to hold tuning properly. d. Are the strings properly wound on the tuner peg? The string should self-lock on itself to eliminate any slippage. How to do it - http://www.prsguitars.com/csc/tuners.html e. If guitar is equipped with a vibrato (tremolo) bridge, locking tuners are a must. 4. Are frets dressed and level? a. Excessive fret wear will cause a note to play out of tune. 5. Is truss rod properly adjusted? 6. Is guitar properly intonated? 7. Are pickups set too close to the strings? a. Pickups that are set too close to the strings will cause the guitar to go out of tune, due to the magnetic pull of the pickup magnets.

Wow - Thanks John!

You're a heck of guy for taking the time to help with this issue. I'm a loyal customer of yours and admire that you help your customers post sale. Thanks again!

DM