A majority of the repairs my shop tends to make involve electronic issues on vintage basses. Every vintage bass consists of the fol- lowing electronic components: pickups, wire, solder, potentiometers, tone caps, and an output jack. In the ‘70s, IC chips and circuit cards were introduced in the form of onboard preamps. This month, let’s explore some common maladies and some easy solutions.
You will need screwdrivers, electronic component
cleaner, thin-gauge solder, a multi-meter and a
30-watt soldering pencil for the following repairs.
Warning:A soldering gun or high-wattage
pencil can destroy your components. If
you are unsure of your repair skills, do not
attempt anything you read in this article.
This is not for the amateur. No one will be
accountable for your errors except yourself.
Electronic maladies come in three common
forms: the noisy, crackling signal, no signal at all,
and bad, thin tone. These issues arise for common reasons: lack of maintenance, age, wear and
tear, and “chicken juice.” Chicken juice is a mystery fluid that always seems to sink into or onto
components. It could be years of sweat, beer, or
burger grease, but we just call it chicken juice.
Crackle and Pop
There’s nothing worse than turning your knobs
or jiggling your cable and getting that famous
crackle not heard since the Sputnik missions.
Fortunately this is probably the easiest repair
of all. This is caused by dirt 99 percent of the
time. Spray electronics cleaner on a Q-tip and
wipe out of the inside of your output jack. Use
the other end to dry and you should be good
to go. I have also seen alcohol on a napkin and
a rolled-up Stridex pad work at gigs.
For your pots, you need to get to them
before you can do anything. If you have limit-
ed experience and a valuable bass, leave this
to a pro. You could tear wiring or damage
your pickguard. Your pots should have a small
gap behind the solder lugs. Spray cleaner
in there and then turn your knobs back and
forth. Repeat if needed.
This next step may start some arguments, as
it is generally not advised, but sometimes you
cannot clear up your pot with just cleaner.
As a last resort before swapping out the pot,
I have seen WD-40 used with good results.
Remember to wipe up all fluid residue.
Thin and Unmanly Tone
Does your bass sound thin? Does it screech?
Do you have low output? Is it unmanly? Son,
we need to talk!
This first nugget applies to Rickenbackers only. I
bet your tail pickup has all the above issues, even
after changing the pickup. I also bet that your
bass is a ‘70s-era production. Begin by removing
your pickguard and looking for three caps. That
is the problem. Two of the caps are responsible
for making your tone pots work, while the third
cap coming off the toggle is an output bleeder.
Now you have a decision to make: do you
modify your bass, running a straight wire and
removing this cap, or is it a heavily-valued bass
that you’d prefer to leave stock? Removing the
cap will open the bass tone and volume up,
but leave this repair to a seasoned professional.
For most other basses, especially Fender
basses from 1967 to 1975, there are a number
of starting points for dealing with tonal problems. Remember that your wiring is only hair-
width gauge that is either a single strand or
braided. There are many reasons for the maladies—we just have to start at the beginning.
My first step is a visual inspection of all wiring.
Are any wires disconnected? If so, there is the
cause of your zero output. Look at every connection—could a strand of wire be touching
something it shouldn’t? If the visual inspection
doesn’t reveal any obvious problems, it’s time to
break out the multi-meter. Ninety-nine percent
of pickups typically read in the 5 to 16k-ohm
range. As a quick rule of thumb, vintage Jazz
bass pickups are about 5.5 to 8.2k, Precision
pickups are about 8 to 12k and Gibson
Mudbuckers are at the high end of the scale.
Using your multi-meter, take a reading at the
leads where they come out of the bobbin. You
will have one of three things happen: you will
be in range, you will have no reading, or your
meter will “spin” and never stop. If you are in
range, you should proceed to the next step. No
reading signifies a dead pickup, in most cases,
and will require the inspection of a pro luthier. If
your meter spins, you’re looking at an open coil,
which will also necessitate a trip to the shop.
If you have a good reading at the bobbin, set
your pots wide open and begin tracing the
path of the suspected bad signal using your
multi-meter. When you find your bad reading,
odds are you will have either a cold solder
joint, where all you have to do is heat it up,
or a bad wire. Simply alligator clip a piece of
wire to the offending section and see if the
signal opens up—you may also find a funny
pot or a dried out tone cap.
Granted, there are countless possibilities when
it comes to tonal problems, but 99 percent of
tonal issues can be found through these steps.
On occasion, I still need an extra set of hands
and will bring my repair to my local guru. I just
had an instance where a ‘73 Jazz bass had a
perfect reading at the pickup, and yet the pickup
was bad and needed a rewind. Remember that
there’s no shame in respecting your grade level.
All in all, a little common sense and patience will
yield a great result. I hope this article saved you
a few sheckles and grey hairs. Until next time,
drop the gig bag and bring the canolis.
Kevin Bordenhas been a bass player since 1975 and
is currently the principle and co-owner, with “Dr.” Ben
Sopranzetti, of Kebo’s Bass Works:kebosbassworks.com.
He can be reached at:Kebobass@yahoo.com.
Feel free to call him KeBo.
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