HELP! Need to know what pots to buy!

I can't tell for sure from the pictures, you might have one volume pot, a balance pot, a bass pot, and a treble pot. Now it seems you have a couple of different issues. The cutting in and out that you fix by whacking it hard--probably a cold or broken solder joint. That battery connector looks cobbled together too. You might even have a capacitor with a broken leg.

The crackly pots...you could try getting a spray can of Deoxit and spraying inside them. That often can help crackly pots. If you need to replace them, though--well, how good are your soldering skills? What test equipment do you have?

If I had that bass here on my bench, and needed to replace the pots, I would start by physically measuring each one--the new pots must match the body diameter, the screw thread size and length, and the shaft size. They must match the pin configuration too, to connect into the PCB. Then I'd determine the electrical value for each pot. Are they audio taper, 500K pots, for example, and is one of them truly a balance pot.

Another option would be to do away with that preamp and convert it to a passive setup. You could make it V/V/T/T with those four knobs.

Oh, and shield that control cavity.

 

+1 to first spraying de-oxit into the pots to clean them up, that's often all that is needed.

then, check and maybe replace the jack and that battery clip.

 

Ok. Bass electronics lessons!

1. First thing to try with crackly pots is spray pot cleaner. The poof can comes with a long tiny tube and the place to try to get it into the pots is hopefully there is a gap just above the contacts on the phenolic board with the 3 terminals. Otherwise you might try the indent on the back of the edge of the case. Often there is an opening there.

2. This is an active bass and pots are mounted on the circuit board. This means that standard pots are not direct replacement. It also means that the pot values may not be standard values. Best would be be a replacement set of pots from bass maker, otherwise you'll need an ohm meter to measure the value ONCE the pots have been REMOVED from the circuit board. Scratch the Ohms on each pot back. Note value is the ohms between the two OUTSIDE terminals.

3. Don't just guess. Figure out what each pot does. You do this by taking a small screw driver or paper clip to tap on the pickups. Doing that figure out which pots are volume and if they are volume/volume or volume/blend. Since this is a P/J configuration it's doubtful that you only have a single volume pot. The other two pots will be "bass" and 'treble" controls. The way you figure those out is by plucking the G string with your fingernail and seeing which pot rolls off the highs or boosts them. The bass is the other one, but it might be easier to test by plucking the B string (or E string you have a string missing) and seeing which pot makes the lows louder and softer. Write down which pot does what in a diagram and scratch it's function on the back (maybe even put labels on the circuitboard near the pots.

4. At this point take off the knobs (set screws or if there are none, they pull off) and take nuts off pots. Pull whole board assembly out of bass. See how pots are mounted to board. If they are just tightened on the board with nuts on the shafts this is good. If they are all soldered on the board with tabs, that is not so good.

5. Buy a solder sucker. (It's a plunger vacuum thingy with a trigger...essential for what you are about to do.)

6. Remove the four pots (you marked them and where they go right?) from the board. You do this by heating each long pin from the pot where it goes through the board and suck the solder out of the hole in the circuit board until the pin is loose and free. When all 3 are free, remove the pot.

7. Once you have the pots removed, measure the ohms on each one. Go on line to electronics supply (like Mouser) and try to find pots of same value with PC pins. This may or may not be easy. Usually you'd pick linear taper for all except volume which will be audio. Linear taper for all of them shouldn't be that bad if it's all you can find. Wrong taper will show up as full action of pot over just a limited rotation. I wouldn't worry about that at first.

8. If you can't find PC mount pots then buy pots with normal solder terminals and you'll have to run wires from the pot terminals into the proper holes in the circuit board for that pot.

I know this sounds complex but it really isn't. Once you go through it, you'll be ready for anything. If possible I do not recommend switching to passive because this is a PJ 5er bass (sweet!) The P-bass pickups and the J pickup will not balance well in a passive circuit. ( I know since I have one!) Active allows them to balance correctly.

Consider shielding if cavity does not already have conductive black paint.

Good luck.

 

Don't worry about that yet. Figure out what needs to be fixed before you toss money into it. If you replace the pickups you'll still have the same issue you started with.

Detoxit is an electrical component cleaner. It will do absolutely nothing for your bridge and saddles.

-Fix the electronics
-Get a new set of strings (do you have the 5th string removed for a reason?)
-Get a setup on the bass

Once those are done the bass will essentially be the best it's going to be in it's current state (assuming it's a good setup). Then you can decide if you want to bother swapping parts. Me personally? I'd probably sell it and get something that better suited what I wanted from a bass.