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Diagnosing P-Bass "Ski-Jump". Worth Fixing?

Discussion in 'Hardware, Setup & Repair [BG]' started by Gilmourisgod, Apr 16, 2017.

  1. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    Mt son is a cadet at Mass Maritime, and plays bass in the school Jazz Band. He has a nice Jay Turser Hofner clone. While digging through a closet packed with old broken music stands and other cast-offs, he came upon this MIM P-Bass, no case, vintage unknown, though I'm guessing it's a 90's bass. Nothing special, and pretty beat up and un-loved. About what you'd expect from a college-owned beater bass passed down from one student bassist to another until it ended up forgotten in a closet. Knowing I'm trying to learn a bit of Luthiery, he brought it home:

    The action was unplayably high, with a clearly visible forward bow. The truss rod has probably never been adjusted. The forward bow seemed to be mostly from first to 5th fret. I got the truss rod to turn and canceled most of the forward bow. I was shooting for .015" relief at the 7th fret, with the first fret capo and 16th fret depressed where it crosses into the body. The G string came into spec after about three 1/8th turns, but the E string is still pretty high. Does that mean I have a twisted neck? It didn't look obviously twisted:
    The other issue is string buzz on E, A, and D strings from the 15th to 19th frets, but none on the G string, even with the action very high. I couldn't find any notably high frets in that section of the neck. is this a classic "ski-jump" neck that could be salvaged by grinding some fallaway in the high registers, or is it just a trashed neck overall?

    Other problems:
    Rusty telephone-cable sized strings
    High nut action
    Crackly pots
    Cracked pickguard around the output jack, which cuts out intermittently.

    The school band director told my son he had intended to throw out this "broken" bass when he got around to it, so it's probably his for the taking. Worth the trouble?
  2. tzohn

    tzohn Guest

    Apr 26, 2015
    Yes it does, it's a fender! What action have you set?
  3. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    Sure, I'd start with a known set of strings, (like Fender 9050ML for flats), a put a fender washer (or Fender washer, :cigar: ) over the cracked pick guard to give you support for the jack. That should get it playable and working, you can go from there. If the pots are scratchy after repairing the jack THEN I'd replace the pots.

    If you have nut files you could adjust the nut, I'd take it to a repair shop and have the nut fixed.

    There are ways to salvage a ski jumped neck, or you could just replace it. Repairing a ski jumped neck with the accepted methods is going to cost as much as a new neck unless you do the work yourself.

    Is this a project bass for you to play with or would you son like to use it? If your boy wants to use it, then I'd try dressing the 15th ~ 20th frets to get rid of the buzz and order a new neck. Then when the neck comes in you can switch the necks out and still have one to mess with.

    You may find this useful, you may be able to do this whether twisted, ski jumped, or both: Rescuing a badly-twisted 1964 Jazz Bass neck
    Last edited: Apr 16, 2017
    Gilmourisgod likes this.
  4. 202dy

    202dy Supporting Member

    Sep 26, 2006
    Not enough data to diagnose. Measurement (everything) will help.

    Buzzing in the upper register could be remedied by changing the neck angle. Until the guitar is properly set up it is impossible to say for certain that a ski jump exists.

    If the instrument is free and you are willing to do the work it will certainly be worth doing.
    96tbird, Gilmourisgod and sissy kathy like this.
  5. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    Thanks for advice. I figured id take a shot at trying to make it playable. So far I've adjusted the trussrod to kill the forward bow, or most of it, next I'll work on the nut slots, the action at first fret is way high, odd because it looks like the original factory nut. I'm comfortable with any work up to and including fret level and crown, but have never done any of the more extreme heat bending or other neck straightening techniques. I had thought of shimming the neck to change neck angle, not sure why it buzzes on every string but the G.
  6. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    first, try adjusting the rod until all the forward bow goes away.

    if you can't do that, then you've got a problem neck which won't be cured by any of the rest of it.
    that's still really bowed.

    .010" from first fret to last fret would be nice.
    xroads, tzohn, 96tbird and 1 other person like this.
  7. Bruce Johnson

    Bruce Johnson Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    From here, it doesn't look too bad. If the truss rod works and gets the relief down into a reasonable range, that's good. It sounds like the 20th fret is high, or it might have a small ski jump condition. Level the high end frets with a sharpening stone and see where you are. It may not need much more than that. New strings, true up the nut slots, etc.
    Gilmourisgod likes this.
  8. If there's a ski jump you'll be able to see it. If it's affecting playability then it's usually easy enough to see. Getting the nut right is a good first move.

    As for the buzz on every string except the G it could be as simple as the G having higher tension and lower mass than the other strings at the same action height.
    Gilmourisgod likes this.
  9. Can't really see much of the neck from that angle really.

    Try posting two more shots:-

    Move the camera over a bit so you can see the fret ends from last fret to nut. (Will show how they line up all the way up the neck)

    Take one on left and one on right.

    Like this:-

  10. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    These photos suck, I'll try again, but I think you can see the forward bow in them, and maybe a hint of ski jump, but I'm not seeing anything that looks like twist.
  11. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    I can't argue with that.
    tzohn, Groove Doctor and Axstar like this.
  12. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    Hard to get much depth of field with an iPhone, but I'll try again. Tough crowd!
    ZenG and JLS like this.
  13. You'll usually see a ski jump from the bridge end. Take a shot from the end of the bass with the focal point around the 14th get.
  14. gregmari


    Nov 27, 2013
    Are you trying to set it up with the Rusty telephone-cable sized strings? I would put some new strings of a known tension on it first.
  15. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    OK, a few observations......
    It took a good bit of turning on the trussrod nut to get the neck to a conservative relief of .012" at the 8th fret with a capo at first, and finger at last fret. The rod is now very tight, nervous to tighten it much more. The nut action is around .022" at the first fret with open strings. String height set to 4/32" at the 17th fret. Its playable, but buzzes badly on E, A, and D strings from around the 15th fret up. The G string has no buzz at all. Using a utility knife blade as a fret rocker, part of 16th fret gives a tiny rock. Any point in messing with neck angle? I'm thinking this is ski jump or a couple high frets, no sign of them coming unseated otherwise. Before I go trying to file some fall away into, any other way to evaluate high register fret buzz? I have a 24" precision ground fret leveler or some very flat 8" long DMT diamond stones that would level things nicely if that's what's called for.
  16. Polish those frets!!!!
    Getting them clean might make a huge difference.

    Replace those strings!!!
    Make sure it's a light to light-medium gauge so they sit deep in the nut slots and put less tension on the neck.

    Check the fret position!!!
    Gently tap a proud fret with butt end of a screwdriver first to make sure it's sitting down in the fret slot properly before filing the fret. Cheaper basses or poorly stored basses can be prone to this. (Great way to fix sharp fret ends too).

    I did those 3 things and got a bad skijump neck 75% better (I was a guitar tech in music shop for a few years). It was definitely playable at that stage. Then took it to a top notch repair guy who got it to perfection.
    Last edited: Apr 21, 2017
  17. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    @Groove Doctor
    Great advice all three points. The bass is filthy, rusty screws, grungy neck, literally never cleaned that I can see. Its never going to be a beauty, but I can at least get all the DNA off it. Do you recall how the tech got the last bit of joy out of yours? Fret level?
  18. Bruce Johnson

    Bruce Johnson Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Yep, the top end frets need to be leveled. They are calling out to you! Whether the cause is a ski jump, a fingerboard lump or whatever, it doesn't really matter. They need to be leveled. No deliberate fall-off, just level with the others.

    Your fine grit diamond honing stone will work just fine. I personally level my frets with a 8" Norton Medium Oilstone, the reddish-brown one. I've been using it for years on all frets, including stainless, and it's not showing any signs of wear. Much more precise and less hassle than sticking sandpaper on bars.

    Use a black Sharpie to color the tops of the frets from 12 up. No need to mask off the fingerboard between the frets, but you can if you want to.

    Wipe a dab of mineral oil on the diamond stone to clean and lube it. Work it over the frets in small circles, stopping to watch what's happening with the black Sharpie lines. Grind away in circles, moving slowly side-to-side across the fingerboard. You want all the frets in that zone to have thin shiny lines all the way across the top, where the stone has worn away the Sharpie ink. The ones with the widest shiny lines are the high frets; the skinny lines are the low ones.

    Light pressure, not much more than the weight of the stone. If the stone starts to load up with brass-colored paste, wipe it off with a heavy paper towel and mineral oil.

    As soon as all the low ones have shiny lines, stop with the circular motion and do a few strokes straight side-to-side across the fingerboard. That puts any scratch lines along the lines of the frets, where they are less noticeable.

    That's it, the frets are leveled. If the shiny lines are fairly thin, like less than 1/3 of the width of the fret, then you don't need to do any crowning. If some particular fret, like the 16th, has a real wide shiny stripe on the top, then it should be crowned to bring the width of its shiny stripe to about equal with the others.

    The easiest way to do the crowning is with a purchased crowning file. However, you can make a homemade crowning file from a small Japanese waterstone, a fairly coarse one. Use the edge of the stone, so you aren't messing up the main flat surface. File a small rounded notch in the edge of the stone using a small round file (that you don't care much about, because it will dull it). The best file is an 1/8" dia chainsaw file, available for cheap at hardware stores. That makes about the right radius notch. Use the notch in the edge of the stone as your crowning file. Touch up the notch as needed with the file.

    Once the frets are crowned, you can polish them with #0000 steel wool. Much faster and easier on the hands is to use the little rubber abrasive wheels from Stew-Mac, in a Dremel tool. I use the grey ones only on stainless frets, and the gray, followed by pink on NS frets. Yes, you need to protect the fingerboard during the polishing. I use one of the Stew-Mac stainless fret polishing shields, trimmed a little narrower and held in place with two strips of black electrical tape. Polish one fret, lift it up, and move it to the next one. The electrical tape is sticky enough that the same two strips will go all the way down the neck.

    All of this takes less time than it took to write about it!
  19. Showdown

    Showdown Supporting Member

    Jan 21, 2002
    Honolulu, Hawaii
    I had the same problem on a 1986 G&L L2000. I got an 8" sanding block from StewMac in 9.5" radius and sanded from the 12th fret up. It only took a few strokes, I was surprised how fast it went. I guess nickel is really soft. Then I used a fret crowning file (also from StewMac) to finish up. Worked very well, good low action now. As Bruce Johnson said, it takes less time than to write about it.
  20. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    Thanks Bruce and Showdown. I'll the level and crown and post back how it works out, id really like to salvage this bass if I can. The frets are overall pretty grungy and tarnished, so I may do a light polish overall.

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