bench testing a pickup

[tomd999]

Hi,

Dragged my 5 string out yesterday afternoon for a fill in gig for my buddy last night. hooked everything up for a check before I headed out... No sound out of the neck pup. No problem, I figure, must be a bad solder joint. Couldn't find a bad joint and time was a factor so I ended up going to my "go to bass", my Pilot and doing half his set with a 4 tuned BEAD. Saved the day for him. (Man, 40 -100's are really, really flappy tuned that low)

Today when I had a chance to go through my 5, it's a lot worse than I thought. After I disconnected the leads from the pots and isolated the pups on their own, the bridge pup gives an Ohm reading across the leads when I test with a multi-meter set at 20M Ohms, the neck pup does not.

So before I pronounce a Lane Poor pup dead, am I testing correctly? I assume that my Ohm meter at 20M would have enough "Umpgh" to overcome the resistance of the windings as evidenced by the reading I'm getting from the one that gives sound.

Would I be better off just soldering the leads to an input jack and trying it hooked up to an amp?

I'm open to some good suggestions from people that have run into this before or repair for a living.

I'm really hoping that the pups not dead as nobody has seen Lane for years and this sounded so sweet.

Tom

[fdeck]

You should get a reading with the pickup. Make sure the tips of the probes dig into the metal a bit, in case there is some coating, oxide, or solder flux where you are testing.

[tomd999]

Update:

I cleaned and re-tinned the lead ends with fresh silver solder, same result.

It's been hotter than hecks half acre around here for the past 3 weeks so I figure what the heck, I stuck it in a ziplock and put it in the fridge. I'll test it again in a couple of hours and see if the temp changes anything.

Tom

[Rattman]

I've never heard of a previously fine-working pickup go completely 'out' that completely before. Not to be condescending but.... how many leads are on that particular pup and what are the lead's colours?

[BigOldHarry]

Let's see..

He gets no sound of the neck p'up...
He gets sound from the bridge P'up
He tests the bridge, gets connectivity
He tests the neck - no connectivity...

Sounds like a wire on the coil broke or came loose. Given that LP p'ups aren't cheap, I'd at least try to see if there is a loose connection from the last wrap of the coil to the solder spot... And I'm sure there are folks who fix p'ups out there...

[tomd999]

Another update

I let the pup sit in the fridge for 3 hours, took it out, tested it right away and got the same resistance reading as the other one that's working. Quickly soldered it to an input jack and hooked it up to an amp, sound!! Let it sit 60 minutes in the warm (75F) air, turned the amp on again, no sound, tested again, no resistance reading. so it's definitely related to expansion/contraction of the components inside the pup.

As the pup is a sealed in epoxy block with a single Teflon/silicon insulated coaxial cable with 2 conductors coming out of the back it's not that easily serviced. I was able to scrape off a small amount of the epoxy on the rear and access the outer shielding side lug on the pup and that side of the circuit is fine, it's the other conductor that is open/broken/disconnected somewhere under the epoxy. I suspect that it would take a skillful machinist with a milling machine to carefully cut away layers of epoxy on the rear until the coil connection can be uncovered

If anyone has any other ideas or knows of a company or individual that does this type work, please let me know.

Thanks,
Tom