Please help me pinpoint problem with my bass

Blazer79 · #1 10-16-2011, 01:57 AM

I have a Washburn MB-6 which I bought about 16 years ago with my first paychecks ever. So, although it's not a "boutique" bass, it's been with me almost all my playing life, so I'm attached to it.

Everything's still original. It has passive J-style pickups and a 9V preamp. It has a switch to select pickups instead of a knob.

Don't worry about the broken cable in case you noticed., that's been fixed.

My usual position is the switch in the mid position to activate both pickups. The problem is that recently, the neck pickup goes almost dead almost all the time, leaving only the bridge PU, which I don't like. by "almost dead" I mean that if you turn the switch to the neck PU only, you can hear it but very softly. So when the switch is in the mid position, the bridge PU prevails.

Interestingly, if I slap all the strings at the same time really hard several times, it comes back. After a while it goes away again, and there you have me slapping like a kid again.

So can someone pinpoint me in the right direction? Is the pickup going bad? Is that even possible given the simplicity of the internals of a pickup? Or is it the preamp gone? Is there some kind of test I could make? I've done some circuits (just following instructions) successfully before, so the soldering gun doesn't scare me.

Oldboy · #2 10-16-2011, 05:13 AM

I read this post with interest.My main reason being that I have a Washburn XB-600 with virtually the same problem.Mine has 2 soapbars and a 2band EQ.My problem was like yours.When I soloed the neck p/up,the sound was weak.In the mid position (both p/ups) the bridge p/up was much louder and had a much bassier response than the neck one.With the bridge soloed it was much the same.In desperation,I removed the pre-amp and installed an Artec Se3A 3band EQ.Results?? unbelievably pretty much the same as before,which makes me think that the p/ups are the problem.
Weird that pretty much the same problem should arise in another Washburn?
I think in your case though that the switch could perhaps could do with a clean or even maybe replaced.The fact that the problem disappears with a bit of 'percussive maintainance' could point to this.I'm subbed to this thread in case anyone else can shed any light.

Blazer79 · #3 10-16-2011, 05:47 AM

Interesting idea about the switch. However, I just bridged it with a piece of cable and didn't wake up.

Another weird thing is that when I start to play, I have to do the "percussive maneuver" several times. But then it seems to warm up or something cause I can play for almost half an hour with no need for "persuasion". Then maybe another half an hour for another persuasion. However I stopped playing and unplugged it for about 5 min. Plugged it back to check your theory and again it was gone. This makes me think maybe a bad capacitor, transistor, whatever in the preamp circuit. But since you mention that a preamp change didn't fix it it leaves me stumped.

Crater · #4 10-16-2011, 06:07 AM

I've had this problem with guitars, I would look at the switch first. Those box-type pickup switches are not so great, replace it with a good quality les-paul style pickup switch.

What are the controls: pickup switch, bass, treble, master volume? If the neck pickup has it's own level control, that could be the problem too. Pickups are the last thing I'd suspect because they're so simple that there's not much to go wrong. If you want to test your pickup you can do so with an ohm meter.

Blazer79 · #5 10-16-2011, 06:16 AM

Thanks Crater.

As I mentioned, I manually bridged the switch with a piece of cable, but didn't work.

My preamp has volume, bass, treble and mic select switch.

Following the wiring schematic, I can see that the preamp only receives one cable from the switch. So it has no way of telling from which pickup it's receiving. Based on that, and the fact that Oldboy did swap preamp and didn't fix it, makes me think it's actually the pickup gone bad.

Followed the cable to that pickup and it just goes into the molten resin on the back of the pickup. Can someone explain to me if it's possible to have a bad pickup? Does the magnet lose its magnetism? Isn't the winding inside fixed by the molten resin? I'm puzzled now.

I'm gonna try welding only the neck pickup to the preamp, bypassing the switch and see what happens.

Arthur Strand · #6 10-16-2011, 06:30 AM

I would suggest taking it to your nearest guitar repair specialist who can diagnose the problem properly and then fix it. Tinkering around with it yourself could do more harm than good. You have no diagnosis so therefore you cannot go ahead with the correct treatment.

ehque · #7 10-16-2011, 07:04 AM

Connect the pickup directly to the jack and test it that way, then you can isolate the pickup from the rest of the elements inside the bass.

The windings in a pickup can and do break, and that can cause a significant drop in volume and that tinny sound.

Oldboy · #8 10-16-2011, 10:58 AM

I've 2 other basses with Artec EQs installed.In both cases,the p/up pan control controls output from each p/up in the normal way ie in 1 position output from the neck p/up,in the opposite position output from the bridge p/up and in the mid position output is balanced between the 2.I believe this is the normal function of this control.On this Washburn,the balance between pickups is very unbalanced,no matter the position of the control,which even after a change of pre-amp is still exhibiting the same effect.Points to the p/ups surely?In Blazers problem it must surely be a component of the EQ.Either a dry joint or a faulty component.Let us know how bypassing the switch and using only the neck p/up goes.Might give that a go myself.

Stealth · #9 10-16-2011, 01:19 PM

The pickup balance might be due to a bad type of blend pot used. Only a blend pot with M/N taper gives a smooth blend transition.

As for the percussive maneuver, I'd say something's wrong with the pickup leads - either there's a cold solder joint on the pickup end of the leads or the blend end of the leads. Take it to a tech, because trying to fix the former yourself might kill the pickup for good.

Blazer79 · #10 10-20-2011, 02:50 AM

Well I finally got to test the pickup connected directly to the phono plug. It gave me the same problems.

So I went and removed it. I discovered that as I removed it it alternately went on and off. So what I found is that the cable that comes out from the molten epoxy is broken

See the pics:

That grey cable has two leads inside. When I wiggle it the sound goes away and comes back. That's why when I slammed the strings it made the PU move, which sometimes made the cable have better contact, restoring the sound.

So for the big question: How can I fix this? Is there a way of melting the epoxy? Even thought of drilling it

Or will I have to replace the pickup? I really don't want to replace it because: 1) The actual pickup is good, 2) There are too little options out there for replacement mics for this size. One is an expensive Delano set and the other is a Bartolini set, but I'm not fond of vintage bass sound, more of a modern sound.

So can anybody shine a light on which is the best route to go?

TIA!

Shoewreck · #11 10-20-2011, 03:41 AM

Epoxy can't be melt without damaging the whole pickup. A chance is that the cable is broken outside the epoxy seal. Try bending it in different places to find it out. If you find where it's broken just cut it there and solder a piece of another cable.
If that fails you may carefully route out the epoxy until you find the original solder points inside. Dangerous, but you have very little to loose - the pickup is already broken.