Intermittant neck LEDs

[BeenDown139]

so i'm playing the recently acquired '03 anniversary fretless last night in the dark when the built-in neck LEDs from the 12th fret up flickered a coupla times and then went dark.  the lower fret LEDs acted kinda flaky at the same time but seem to be OK now..  so after a little wailing and gnashing of teeth, i tried the easy stuff first:  new batteries, go over the wiring in the control calvity from the battery loom to the where it goes up in the neck inside the truss rod cavity.  i can find no fault in the visible wiring.  wiggling the wiring where it's accessible is no help.  gently thumping the bass has no effect.   i suspect some of the wiring in the neck has gone wonky.  i also suspect this is one of the few spots on the bass that are inacessible without major surgery at the mothership.  pretty sure the waiting line for repairs is past my lifeline not to mention a come-on-outta-retirement repair bill

so other than only play the bass in a well lighted room or learn the upper registers completely by feel and ear, anybody got a suggestion?

[KR]

I don't know that circuit, and am probably way off, but if the input jack enables the LED switching in any way...maybe try plugging into the jack many, many times --just in case that could help. That's all I got.

[BeenDown139]

thanx for the suggestion but on this one the LEDs are controlled by a switch by the input jack.

as i was sitting in the hot tub evaluating some new high-grade from world of weed (gotta go to commerce city to score but it's the best weed in town i'm telling ya) i came up with a last-try hail mary play:  i tried cutting a small slit in the insulation that feeds the dead LED string up in the truss rod cavity, hooking a clip lead to it and bypassing it all the way to the dropping resistor on the switch (i checked the restor and all its soldering btw).  the operational theory was that maybe there's a break in the wire 'twixt here and there but it was a dead end. 

all the wiring from the truss rod cavity cavity to the interior of the neck is pretty well immobilied and i'd be surprised to see a mechanical failure there.  but i'm grasping at straws at this point.

as far as i can deduce, these LEDs are arranged in 2 strings of 6 LEDs fed by ~27 volts from 3x9-volt transistor batteries in series.  the two strings are in parallel while the LEDs in the strings are in series.  my fear is that either an LED failed open (they should last forever but maybe one took a stray alpha-particle hit or some its protons decayed into elementary particles or who knows wtf). another possiblity is a solder joint failure somewheres in the string.  as far as acessibilty goes, it really doesn't matter - they might as well be on the dark side of the moon.

i guess it could be worse.  maybe going blind in one eye made its hearing better becausethe bass still sounds so good i might have to get rid of the dog.  at least the lower register LEDs still work.  so far.

[lbpesq]

My ‘77 Series 1 12 String has one LED that sometimes goes out when I fret the string on that fret.   It seems to come and go with the seasons.   I suspect the humidity changes has something to do with it and that the fret tang somehow shorts out that particular LED when pressure is applied.

Bill, tgo

[BeenDown139]

well they completly died last night :-(

gonna have a local luthier take a look at it but i'm pretty sure i know what the answer is.  this one's got me scratchin my haid.  the only thing i can tink of is that itseemed to happen when the air got humid around here.  all my bass necks went wonky in celebration (the essence actually bent over backwards if ya can believe it!  ) so maybe something expanded and pinched something else?  maybe they'll come back when the air dries out?

 graspin at straws here.  if this thing didn't sing like 10,000 songbirds it'd be outta here.  arrrghhhh!

[mica]

Sorry you are dealing with this, but it sounds like there is a component or solder failure. It's rare but it does happen. It's not a cheap fix, but it can be restored.

Unless the issue is with the wires you can see in the cavity (and under the truss rod cover and the neck pickup (it's useful to check there to see if the wire got pinched, especially if you have replaced a pickup or suspect a previous owner did)), the problem isn't repairable without removing the fingerboard.

[BeenDown139]

thanx for the input, mica.  you've confirmed what i suspected. 

this one of the strangest component failures i've ever seen.  i got up in the truss rod cavity with a dental mirror and nothing looks out of order.  after i heaved a frustrate sigh yesterday, i reassembled the bass, played the dickens outta it and put it up on the rack.  for some reason i left the LEDs on in the forlorn hope that now the rainy weather is gone for a coupla days, maybe everything will dry out and contract a little, maybe.  it has been an exceptionally wet rainy spring here in the mile high, first time i've seen the sun in a few days.

to get back on track - i got up to let the dog out early this morning to do her business.  as i pass the bass corner i notice a faint glow from the a-bass LEDs.  the lower register LEDs are very, very faintly on, almost at the limit of my dark vision (which is very good, btw).  like they're letting light out one photon at a time. 

so i'm gonna let it be.  maybe they come back.  maybe they don't.  guess it'll be my kid's problem when they try to sell it after i kick the bucket  :-)

[edwardofhuncote]

Drill 'em out and inlay Luminlay. I mean, the fingerboard has to come off anyway to replace them.

[BeenDown139]

this morning they brrighter again.  almost visible in low light.  got an idea about this.  gonna try someting....

[dannobasso]

I have quite a few led equipped Alembics. I have found that the switches can be fussy and need to be exercised quite a bit. They ofen need to be finessed to gert them to turn on the lights at full strength. Move the switch to the on position and then a slight bit of backward pressure to get them to cooperate. Perhaps you are experiencing a similar issue?

[BeenDown139]

....I have found that the switches can be fussy and need to be exercised quite a bit. Th

i completely bypassed the electronics in the control cavity and wired directly to the wires where they go up into the truss rod cover to completelty eleminate the possibility of any failed components/wiring  in the control cavity. no soap.

so the lower register LEDs have come back  bright enough to use in very low light, which is one of the main reasons i bought this bass.  the LED at the 9th position is dark and i suspect he's the failure in that string.  almost like it's turned into a very low current constant current diode.  doesn't matter how i vary the supply voltage or dropping resistor, the LEDs stay the same brightness.  strangest component failure i've ever seen.  the upper register LEDs are still dark.

so i'm gonna live with it.  ain't got much choice.  played the bass for about 45 minutes in the late afternoon sun yesterday until my hands hurt.  this bass feels more like a cello or a violin than a bass guitar.  absolutely amazing.

[BeenDown139]

this jsut keeps getting stranger.

i've been leaving the LED switch on 24/7 to see what happens.  they were faint as a whisper after we got up and had our walk and a coupla morning buzzes.  get on the bike and go roll a dozen miles.  come back and all of the upper register LEDs are going full steam.  wtf!?!

the air's dried out a little today but it's fixin to rain.  again.  and again.  guess i oughta check  hte action and see if it's gone wonky the other way now.   please stand by momentairily....

well it still plays like a dream.  guess i'll smoke some more dope, go sit out in the hot tub, watch the thumderstorms roll in and think about this a spell.

[garyhead]

How about a buildup of static electricity?

[BeenDown139]

How about a buildup of static electricity?

well it's been soggy as hte deep south for the last week here, got another wet week to go.  i think the only static charges around here are the nimbostratus clouds that have been rolling over in a nearly continuous wave.

thay quit again last night at the end of a vigorous set just as the room was getting dark and my hands were flaming out.  dark this morning.  but it's fixin to rain.  again.  and again.  we shall see when teh sun comes out.  maybe.

[lbpesq]

Just a thought:  how about putting some rice in the control and truss rod cavities and let it sit for a day or two?  The rice should absorb any moisture.   

Bill, tgo