Fret buzz with half step tuning: low nut or neck relief?

[Acapulco Gold]

My 1986 San Dimas Soloist has developed a low E string buzz in the open position. No matter how high the action there is an audible fret buzz when playing the low E open. I had just put on 10 gauge strings to try it out in half step tuning, it had 9's tuned to E and it was ok. Now I put on the 10's and they do feel looser. I didn't touch the neck relief, set the action to as low as it can go with all the other strings playing and sounding fine, low E buzz no matter the action.
I have just put a capo on the 1st fret to check relief, it is around .013. With the capo in the 1st fret there was NO low E buzz, even when plucking hard, take the capo off and there is an audible buzz no matter how lightly I pick.
So this means the nut is cut low? It was fine with 9's, I haven't yet put the locking nuts on the nut, while the tuning settled but I don't think locking the nut will get rid of the low e buzz.
Any other solutions in neck relief setup?

[MetalMedal II]

There could be a flaw in this specific Low E string causing the buzz. You mentioned you just placed these strings on. I'd try replacing this one string with another of the same gauge. BTW, does this '86 soloist have a standard Floyd nut or a behind-the-nut string lock, like a Kahler has? If it's the former, I tend to go with what I first wrote. If it's the latter with a regular nut, the nut slot for that string could be worn down enough to cause the buzz. If that's the case, I'd use 2-part epoxy or super glue to build up the slot to stop the buzz. But, I'd first try replacing the string first to see if it goes away,

[DonP]

Another way I've read about to build up a nut slot is super glue and baking (soda or powder - look it up I don't remember)

[1337storm]

The easiest way to check the nut height is to put a capo between 2nd and 3rd fret so the string are fretted on the second fret and check the string height on the first fret.
There should be a small gap between the strings and the 1st fret (how much depends on the same things as for when you set string action, string gauge, tuning, pick attack and so on).
For a general recommendation just use google or YT.
But anyway you can easily check if the low E is lower then the rest of the strings or not.

[pianoguyy]

The easiest way to check the nut height is to put a capo between 2n

Don't use a capo. Use your finger.

[pianoguyy]

I would definitely lock down those locks, just to make sure it isn't playing a role in the buzz.

[Acapulco Gold]

Thank you for the advice. I decided to change strings and go back to standard tuning. WIth the 10's in E flat the guitar sounded great for rhythm but thicker for lead so I changed back to 9's.

The low E is more buzz prone than the other strings. I straightened the neck quite a bit, as it had a lot of relief, and raised the strings until the buzz all but disappeared. The action is at least 2mm now, a little higher than I like it but I do like playing the guitar with no buzz. I'm still getting used to the Jackson compound radius and floyd rose for ultimate setup.

I will give it a few days for the new strings and neck relief to settle before I do anything else. I am hesitant about reducing the relief because I have done it 3 times already, but all my other guitars have a straighter neck but this feels better already. Will check the nut, but this guitar is from 1986, it could easily need few spots looked at. Still sounds killer though!

[DanzoStrife]

I just got my guitar done. The PLEK was already done, but when I took it home it was buzzing again. Increasing the relief to .012 did not help fret buzz at 5-12 fret. Action was 1.5mm, but no good like a bee. Having more relief should've helped the buzz right? WRONG, it was worse..

So I took it back, said the neck didn't get much time to settle. The scan was done again real quick in the machine, and he said they just needed to tighten the truss rod. It was now at .006, action at 1mm at the low E. So now I have lower action , less relief and less buzz. I don't even how this even makes sense to me? But so my point is that the opposite might work for you too! (No they didn't charge for that, and I can get that done again if i need to).

EDIT: have u measured neck relief?
LIke if u fret your 3rd fret on 6th string can u still press down the 1st fret on that string? There should be a certain space between first fret and open string too.

Thank you for the advice. I decided to change strings and go back to standard tuning. WIth the 10's in E flat the guitar sounded great for rhythm but thicker for lead so I changed back to 9's.

The low E is more buzz prone than the other strings. I straightened the neck quite a bit, as it had a lot of relief, and raised the strings until the buzz all but disappeared. The action is at least 2mm now, a little higher than I like it but I do like playing the guitar with no buzz. I'm still getting used to the Jackson compound radius and floyd rose for ultimate setup.

I will give it a few days for the new strings and neck relief to settle before I do anything else. I am hesitant about reducing the relief because I have done it 3 times already, but all my other guitars have a straighter neck but this feels better already. Will check the nut, but this guitar is from 1986, it could easily need few spots looked at. Still sounds killer though!