Why will PRS not stay in tune

Winny_Pooh

CavemanGrogg said:

Because they copied the designs of guitars famous for having tuning issues.

Lazy

Barney

ICBM said:

Does it stick out of tune in the same direction as the last trem movement - ie flat after a down-bend? If so, it’s the bridge. Or the opposite - sharp after a down-bend? If so, the nut or possibly the tuners.

Are the tuner key screws overtightened? PRS do that. Release the tension slightly so the little spring washer between the key and the tuner body has a tiny bit of give in it.

It usually drops when I use the trem ...sometimes a wiggle about with the trem will sort of put it right 

I do know what you mean by the tuner key screws ...do you mean the ones that are screwed into the wood to hold the machine head secure or the single screw on the side of the head 

BillDL

No, he means the screws through the buttons (keys) of the tuners.  They have a spring washer as well as a nylon washer between the button and the body of the tuner that provide pressure so the buttons aren't too loose to turn, but if you crank the screws in too tight it can cause issues.

Barney

BillDL said:

[EDIT: Already mentioned my @Stevepage earlier that I hadn't seen, but in more detail below]

The trem bridge with 6 fulcrum screws at the front of the bridge plate?

If so the screws probably have a cleft in the smooth part of the screw shank just under the head around the full circumference. I'm not sure if they all have this on the screws, but the ones I've worked on in the past have had this.

Although it does matter on a 6-screw vintage style Strat trem, it isn't quite as crucial as it is with these PRS trems to have all 6 screws set at exactly the same heights so that the chamfered edge of the holes in the bridge plate all sit in those pivot points at the same heights.  The 6 screws that act as the fulcrums at the front of a vintage Strat bridge do not have those rebates cut into them and only use the smooth shank of the screw to pivot on, so it doesn't matter quite as much whether they are set to exactly the same heights.  The usual indicator of uneven height screws is a plinking or plonking noise as you use the trem, and it can mess with the tuning stability.

From memory the indentation is something like 2 or 2.5mm below the underside of the screw head.  I found that the easist way to make sure they are all the same height is to first have the trem set to the desired or recommended height off the body, which is something like 1/16" (don't quote me on that - it's documented in lots of places), and then relax all the strings and springs so that the bridge plate lies flat on the body.  Using a gauge of the same thickness as the distance down from the bottom of the screw head to the indented ring on the screw, you can insert that between the top of the bridge plate and the underside of the screw and set all the screw heads to the same height so the indented rings are all exactly in line.  One thing you don't really want to be doing is turning the screws too much with full string and spring tension on them because it can blunt and deform the fulcrum points.

Thereafter it's a case of trying to minimise friction at all points of contact, especially the nut slots.  The "nut sauce" stuff is reputed to be very good, but I buy much cheaper Labelle 206 grease with teflon (PTFE) that's intended for model cars, planes, trains, etc. and it works extremely well in nut slots, string trees, and breakover points on saddles.

https://therailwayconductor.co.uk/model-railways/model-lubrication/product/labelle-206-hi-performance-rc-model-grease

Watch THIS official PRS video from 10 seconds in and keep repeating the section right at 0:13 as the trem bridge is being lowered back to the floating position.  You will see the bass side suddenly making an odd movement.  That's very likely to be caused by misalignment between the groove in the screw and the edge of the hole in the bridge plate, and that kind of thing can cause "return to pitch" tuning issues.

Thanks very much ..I did look at these screws a few days back but I didn't realise they had a groove like in the pic I didn't think they looked the same height but wasn't sure but thought it wouldn't matter ...but it would probably explain why sometimes i think it is ok then other times goes out ...it's maybe clicking in and out of place ...I'm going to have another look .

Barney

BillDL said:

No, he means the screws through the buttons (keys) of the tuners.  They have a spring washer as well as a nylon washer between the button and the body of the tuner that provide tension so the buttons aren't too loose to turn, but if you crank the screws in too tight it can cause issues.

Thanks will check these as well 

normula1

When you changed strings did you knock the bridge out of the notches in the screws? I somehow managed to do this once

guitars4you

guitargeek62 said:

Note: DO NOT ADJUST THE BRIDGE SCREWS WITH THE STRINGS UNDER ANY TENSION

This by the bucket load

Musicwolf

normula1 said:

When you changed strings did you knock the bridge out of the notches in the screws? I somehow managed to do this once

I did the same some years ago

57Deluxe

chris78 said:

Only ever had one issue with a PRS going out of tune and it was the nut.
The whole point of a PRS is that it stays in tune

was going to say same thing... often quit bulky nuts and not always well slotted.

koss59

The DGT Core I had needed pencil lead in the nut. They’re not cut as well as you’d think they would be.

Funkfingers

Barney said:

Funkfingers said:

Have a look at the string ball ends in the vibrato sustain block. Are they all seated properly? Are the wraps around the end of each string unwinding?

Have you recently changed to a heavier string gauge?

D'Addario Balanced Tension 10-46 string sets come with a 13.5 thou B string. I recently put a set on a friend's guitar. The B was catching in its nut slot. A quick rounding with a slotting file cured the problem.

•

How old is your PRS CU24? The gears inside the Schaller "wing collar" machineheads eventually become sloppy. 

Funkfingers said:

Have a look at the string ball ends in the vibrato sustain block. Are they all seated properly? Are the wraps around the end of each string unwinding?

Have you recently changed to a heavier string gauge?

D'Addario Balanced Tension 10-46 string sets come with a 13.5 thou B string. I recently put a set on a friend's guitar. The B was catching in its nut slot. A quick rounding with a slotting file cured the problem.

•

How old is your PRS CU24? The gears inside the Schaller "wing collar" machineheads eventually become sloppy. 

I'm using the D'aAddario NYXL 9 to 42...the guitar is a 2001 model 

I appear to be talking to myself, again.

ICBM

One serious problem that you might find is that sometimes, the bridge is very slightly ‘dished’ across the screw holes, I think due to shrinkage as the casting cools. This means the screws need to be set in a very slight curve, lower in the middle than at the ends, so all the notches match the knife edges. It’s actually not too hard to find the correct positions by feel, if you rock the bridge with the arm - with the strings off, or at least fully slackened - while turning the screws carefully.

I’ll see if I can find a pic…

Jay100

I have a Core Custom 24 (currently up for sale on here ) and it’s tuning is rock solid with the trem floating. 

Barney

ICBM said:

One serious problem that you might find is that sometimes, the bridge is very slightly ‘dished’ across the screw holes, I think due to shrinkage as the casting cools. This means the screws need to be set in a very slight curve, lower in the middle than at the ends, so all the notches match the knife edges. It’s actually not too hard to find the correct positions by feel, if you rock the bridge with the arm - with the strings off, or at least fully slackened - while turning the screws carefully.

I’ll see if I can find a pic…

Thanks ..so iff I took the strings off or loosened them I wonder by turning the screws I should here them click in ..I'm starting to think it is the bridge that's the problem now 

ICBM

Found it - you should be able to see that the bottom of the bridge is curved, where it should be straight.





The screws won't actually click into the grooves since they won't be fully out, but you should be able to feel a 'position of least resistance' as you turn the screws. You should only need to adjust the middle four.

After I did that, it stayed in tune perfectly.

Barney

ICBM said:

Found it - you should be able to see that the bottom of the bridge is curved, where it should be straight.





The screws won't actually click into the grooves since they won't be fully out, but you should be able to feel a 'position of least resistance' as you turn the screws. You should only need to adjust the middle four.

After I did that, it stayed in tune perfectly.

Thanks very much I'm going to try it now 

Barney

Barney said:

ICBM said:

Found it - you should be able to see that the bottom of the bridge is curved, where it should be straight.





The screws won't actually click into the grooves since they won't be fully out, but you should be able to feel a 'position of least resistance' as you turn the screws. You should only need to adjust the middle four.

After I did that, it stayed in tune perfectly.

Thanks very much I'm going to try it now 

I just done the screws now and the one under the G string feels really loose when screwing it in ...sort of like the hole is a bit bigger ...normally i would put a mach

ICBM

Barney said:

I just done the screws now and the one under the G string feels really loose when screwing it in ...sort of like the hole is a bit bigger ...normally i would put a mach

I wouldn't - unless its actually rattling it won't do any harm for it to not be tight, and if you plug the hole you risk pushing the screw out of position which will make things worse.

That does make me think someone has been buggering around with it though.

Barney

ICBM said:

Barney said:

I just done the screws now and the one under the G string feels really loose when screwing it in ...sort of like the hole is a bit bigger ...normally i would put a mach

I wouldn't - unless its actually rattling it won't do any harm for it to not be tight, and if you plug the hole you risk pushing the screw out of position which will make things worse.

That does make me think someone has been buggering around with it though.

I think they have been because when I got it the wings on the machine heads were the wrong way around so I changed them over ...I am reading the distance between the bottom of the screw and bridge plate should be 2.5mm and you can use a 2.5 mm Allen key to put under to get this right ...I have tried by just feel but I'm not sure IV got it right ...so I have ordered a Allen key off eBay and hopefully that will get me in the right place 

Philly_Q

Barney said:
I am reading the distance between the bottom of the screw and bridge plate should be 2.5mm and you can use a 2.5 mm Allen key to put under to get this right ...I have tried by just feel but I'm not sure IV got it right ...so I have ordered a Allen key off eBay and hopefully that will get me in the right place 

Bear in mind that 2.5mm is with the bridge plate sitting flat on the body, not when the knife edges are sitting in the notches in the screws.  You might have already seen this John Mann video, but I think it's worth mentioning.  He talks about height adjustment from about 8:30.