Troubleshooting - Any danger in straight wiring?

ack1961 · March 30, 2013, 06:52:36 AM

I apologize if this is a lame qustion, but I was troubleshooting a bass last night where the tone pot (on a V/V/T passive P/J) was acting like the master volume.
I had a feeling that the Cap may have been shorting against another lug on the pot when pressed into it's cavity.

Anyway, I was trying to isolate the problem and was getting frustrated. A new Cap didn't change anything - neither did a new Tone Pot w/ a new Cap. I ended up eliminating the pots altogether to start from scratch. Now, I have all the Hot (white) wires wire-nutted together and all the Grounds (black) wired together. I wanted to check and see that both pickups and Output Jack worked properly before I went on to troubleshoot further.

Belive it or not, it doesn't sound bad - I have a little bit of hum that goes away when I touch the bridge with my hand, so I suspect I have a Bridge Ground issue. The pickups are on full and it sounds like they would if I have the Tone rolled all the way on. Depending on where my fingers are (at the neck joint , over the P, over the J), I can really get quite distinct tones. It's kinda neat to not have any knobs on a bass.

I intend to get new Pots (I'm guessing that 250k is the way to go for V/V/T) and a new Cap (.47 uF?) and replace the Bridge Ground wire, but I was curious to know if I could possible be doing any damage to the pickups by straight wiring for the time being?

Any useful advice would be welcomed.
Steve

Dave W · March 30, 2013, 10:46:11 AM

You won't damage the pickups by going straight out. You do have a ground issue somewhere.

Is it possible the bass was wired wrong, or is the tone pot issue something that just recently happened?

ack1961 · March 30, 2013, 11:30:43 AM

Quote from: Dave W on March 30, 2013, 10:46:11 AM
You won't damage the pickups by going straight out. You do have a ground issue somewhere.

Is it possible the bass was wired wrong, or is the tone pot issue something that just recently happened?

Thanks, Dave.
I wired the bass after I received the custom pickups, so there is a decent chance that I fudged the wiring (I'm thinking 2:1 odds), but I don't recall this Tone Pot issue before. Granted, I usually play with the tone rolled back, so maybe I just didn't notice...

I just came back from Sam Ash, and I have 3 new 250k Pots, and a new Output Jack - I might as well just change everything while I'm in there (including the Bridge ground wire). I'll pay closer attention to the wiring diagrams, but I double-checked my work against several diagrams. It may have been a sloppy solder joint or something along those lines.

Thanks for the reply.

ack1961 · March 30, 2013, 06:32:24 PM

Ok, one final (I hope) question/concern, if anyone can help:
I swapped out everything and shielded the cavities. It is dead quiet now - no humming and it sounds great.

One remaining issue is the Tone Pot range. I think I have a value problem - here are the symptoms.
With the Tone knob at 100% I get all the higher tones you'd expect. Sounds completely normal for full-on tone.
When I roll it back towards 0, the tone tapers off the highs until I get to about 30% of the pot's rotation range (where it sounds like you'd expect wen you're completely rolled off the Tone knob), then it acts like a master volume from 30% to 0%.

Is this a Capacitor value issue?
Now the embarrassing part - I don't know what value Cap I have in there. Even with my eyeglasses on , I could have sworn I saw 48xxxx on the cap before I buttoned everything up.
I forgot to mention that the Pots were all "AllParts" 250k Audio Taper. Should I have used a Linear Taper pot for the Tone?

Thanks.

Dave W · March 31, 2013, 12:05:56 AM

The audio taper should be fine; most passive basses with J-type wiring that I've tried act like this to some degree, maybe even starting at 30%. Doubt it's a cap value issue, and you seem to have eliminated any other cap issues like shorting or failure. If you're sure you wired it properly according to a standard v/v/t diagram, it may just be normal.

Does the effect change with both volumes all the way up, as opposed to one or both volumes not being all the way up? If so, it's probably normal.

ack1961 · March 31, 2013, 04:53:34 AM

Quote from: Dave W on March 31, 2013, 12:05:56 AM

Does the effect change with both volumes all the way up, as opposed to one or both volumes not being all the way up? If so, it's probably normal.

Yes - the Tone roll off reacts the same at all volume levels. Like you alluded to - it's really not a big issue. I may just put the tone knob where I like it and lower the knob against the body so it can't be moved (my son and his bandmates are all welcome to us any and all of my basses, and they do).

Problem? What problem?

Thanks for the replies, Dave - much appreciated.
Steve

rahock · March 31, 2013, 05:43:08 AM

Both of my Ps the tone rolls off somewhere in the 25-30% range. I've always considered this normal

.
Rick

patman · March 31, 2013, 07:31:31 AM

oddly enough, on a Fenderish bass, I've always run it with everything wide open all my life...When I first started an older guy told me to do it that way, and I've never changed.

Highlander · March 31, 2013, 12:43:42 PM

My answer has always been remove the control circuit altogether... works for me...

exiledarchangel · March 31, 2013, 01:25:52 PM

No damage done mate, my P is straight to jack from birth, and its still alive!

ack1961 · March 31, 2013, 02:13:17 PM

Thanks to all.
I might just go back and wire this one full out and use the pots in another project.

Psycho Bass Guy · March 31, 2013, 02:26:18 PM

Quote from: ack1961 on March 30, 2013, 06:32:24 PMOne remaining issue is the Tone Pot range. I think I have a value problem - here are the symptoms.
With the Tone knob at 100% I get all the higher tones you'd expect. Sounds completely normal for full-on tone.
When I roll it back towards 0, the tone tapers off the highs until I get to about 30% of the pot's rotation range (where it sounds like you'd expect wen you're completely rolled off the Tone knob), then it acts like a master volume from 30% to 0%.

The issue is with the tone pot's resistance: it needs to be lower, which also means that you'll probably need to change the tone cap to a higher value. Since 250k is standard and about as low as you normally find, I suspect that you have a serious imbalance between the output of the P pickup and the J pickup. You could wire a resistor in series with the output of the hotter pickup. It will give a better functioning tone control as-is and also thin the hotter pickup's tone somewhat.

Highlander · March 31, 2013, 03:24:41 PM

Steve... I've found that when playing with just your fingers you can get all the "tone" control you need... mind you, I sometimes use a single volume pot as an on/off switch...

ack1961 · March 31, 2013, 04:55:57 PM

Quote from: HERBIE on March 31, 2013, 03:24:41 PM
Steve... I've found that when playing with just your fingers you can get all the "tone" control you need... mind you, I sometimes use a single volume pot as an on/off switch...

So true - I was demonstrating that to my son. Playing between the neck pickup and the neck pocket gets you that deep bass sound that personally I love so much. Playing directly over each pickup accentuates that pickup's characteristics that much more. Where you play certainly demonstrates a huge array of tones.

Another good day - my soldering is improving and I learned a ton about basses.
Thanks all.