Vintage Bass Electronics: Simple Logic for Common Issues
Is your vintage bass crackling, popping, or just plain weak? Here are some common fixes to try.
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 Borden has 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.