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FDP Forum / Guitar Mods, Repairs, and Projects / Wiring Diagram for SCPB
(This message was last edited by uncle stack-knob at 02:33 PM, Feb 12th, 2012)
FDP Forum / Guitar Mods, Repairs, and Projects / Wiring Diagram for SCPB
Saddletramp
Southeast Louisiana
100.3 FM, KLRZ, LaRose, LAFeb 11th, 2012 06:39 PM Edit Profile Print Topic Search
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I have a Pink Paisley SCPB. Tone control not working; loses vol when going to bass. My Blueflower SCPB works perfectly; the only connection on the tone pot is the cap from #2 to #2 pot on the vol pot. Everything else is wired to the vol pot. Nothing at all like the Mike Dirnt (if that means anything)
Peegoo
Contributing Member
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That chicken
is WRONG, baby.Feb 11th, 2012 07:00 PM Edit Profile Print Topic Search
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Make sure the pot has not rotated and allowed the solder tabs to contact the side of the cavity. If there's shielding paint or foil there, it can ground out the signal as you roll off the tone control.
Loosen the tone pot's nut and enter the solder tabs so the middle tab is pointing directly at the center of the volume pot. Hold it in place as to snug the nut back down.
Check the volume pot for looseness while you're in there too.
mrfix
canadaFeb 12th, 2012 02:01 PM Edit Profile Print Topic Search
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I suspect the problem is the capacitor. It is either too big or has become defective, increacing capacitance and consuming most of the output to charge up. Any chance you have one of the old style paper oil caps ? These are prone to failure.
uncle stack-knob
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united kingdomFeb 12th, 2012 02:32 PM Edit Profile Print Topic Search
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The connections appear odd.
I would expect the no2 leg on the volume to be used for the hot out to the jack.
The scpb wires like a precision.
Scroll down for the wiring.
Te 52
'52 Tele + Delirium
= Tellurium 52Feb 12th, 2012 05:33 PM Edit Profile Print Topic Search
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Could also be wired like this (link). Looks different, but is electrically identical to uncle stack-knob's linked diagram.
There is no way the tone cap can function if only one of its solder lugs is connected to anything.
FunkyKikuchiyo
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New EnglandFeb 13th, 2012 10:23 PM Edit Profile Print Topic Search
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Another vote for defective capacitor. Ceramic disks have a failure rate high enough that it isn't unthinkable. I've had it happen with a few instruments.
Saddletramp
Southeast Louisiana
100.3 FM, KLRZ, LaRose, LAFeb 14th, 2012 07:25 AM Edit Profile Print Topic Search
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Thanks for all the info; I'll open it up again this weekend. The cap. on both is the green "Chicklet" type; any suggestions on what cap. to replace it with? Also, as cheap as they are, I think I'll order new mini pots and a cap
wrnchbndr
Contributing Member
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New Jersey
The otters threw me outFeb 14th, 2012 07:41 PM Edit Profile Print Topic Search
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For the novice, shotgunning two pots and a cap and then wiring according to an established diagram is not a bad idea -- money well spent. Get a new switchcraft output jack while you have the soldering iron hot. The wiring diagram from Uncle Stack is about as good as it gets.
FunkyKikuchiyo
Contributing Member
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New EnglandFeb 14th, 2012 07:43 PM Edit Profile Print Topic Search
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chicklets can have that problem, too.
For value, anything between .01 uf and .1 uf will work. .047 and .022 are the most common. For type, I would be curious where you're getting the caps before suggesting specifics. No sense in ordering from a place for just one cap.
Ones I like: anything Mojo (dijon or vitamin-t), Mallory 150 series, Sprague Orange drop (a few different kinds, they're all good) and a few others... if you just want to go to radio shack, the generic polyester/mylar ones are just fine.
Ones to avoid: electrolytic caps, tantalum caps, or anything polarized.
I personally avoid ceramic disks. They have a distinctly strident sound (albeit subtle) but many would disagree with me, so if it is what you have on hand and it doesn't bug you, then there isn't anything to worry about.
Saddletramp
Southeast Louisiana
100.3 FM, KLRZ, LaRose, LAMar 7th, 2012 07:44 PM Edit Profile Print Topic Search
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Thanks to Te 52 for the wiring diagram and FunkyKikuchiyo for the info on caps. SCPB wiring diagram shows the cap to be .05. So, looking at Allparts, I see (2) 200v Orange Drop Capacitors: P/N EP-4382-000, .022 MFD and P/N 4382-000, .047 MFD . For Pots I see EP-0185-000 Mini Pot. (looks like the volts don’t matter)
Pots have a split shaft but that should be no problem; the ones on the bass are solid but I see no solid shafts anywhere. So, for the price, I may as well order both value caps and new pots; am I on the right track? Hope I don’t bother you guys anymore – you have been a lot of help. Thanks
Te 52
'52 Tele + Delirium
= Tellurium 52Mar 7th, 2012 09:31 PM Edit Profile Print Topic Search
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The orange drop caps should be fine, whichever value you prefer. Allparts has plenty of full-size solid shaft pots (link). There's nothing really wrong with mini pots, but you shouldn't need to use them on a normal Fender bass.
Saddletramp
Southeast Louisiana
100.3 FM, KLRZ, LaRose, LAMar 24th, 2012 09:47 PM Edit Profile Print Topic Search
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It's me again. Replaced both pots and the cap. Still the tone control drops the volume to nothing when I turn it to the bass side. (but the tone seems to get deeper-just the vol drops to nothing) Someone said maybe it's "shunting", that the tone pot is grounding out. Any ideas of where to look? Thanks
Saddletramp
Southeast Louisiana
100.3 FM, KLRZ, LaRose, LAMay 11th, 2012 09:01 PM Edit Profile Print Topic Search
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Well, after taking it to a second tech, he finally tested the pick up. It had much lower output value the the other matching SCPB so I have a Bass Lines SCPB Quarter Pounder to install. Can some one tell me how I use a Multimerter to check it myself, along with pots and caps in the future? Thanks
GP
Contributing Member
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SW Burbs of Chitown
Defend yourself with a pointy headstockMay 11th, 2012 11:12 PM Edit Profile Print Topic Search
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To test pickups on a PB,there are to seperate coils. 2 wires for each coil. Set your meter to ohms on a scale of 10k or higher for pickups depending on the type of pickup you test. If your meter is auto ranging, just set to ohms. Measure across the hot and ground leads of the pickup and that will give you a ohm reading.With the pickups connected together, that reading could be higher or lower depending on how the 2 pickups are wired together. If the pickups are wire in series. One hot from one pickup wired to the ground of the other pickup, the other 2 wires left will be a hot and a ground. The 2 wired this way will have a higher resistance reading. A example would be if one coil measured 6k ohms and the other was 6k ohms, the ohms reading will be 12k. If the pickups are wired parallel. Both hots wired to each other and both grounds wire to each other, the reading will be less. Example is the same, two coils each measure 6k ohms. The ohm readings will be 3k ohms.
To test pots, the two outside pot lugs will be the total ohm rating of thee pot when measured with your meter tested in ohms. If you have a no load pot. These two outside lugs will show a open circuit as one lug is not part of the the resistive material. It is seperated and really is there for nothing. I will only measure on the middle and one outside lug. A example will be a 250k pot. When turning the pot all the way to one direction, the outside lug that the direction you turned it to should measure 0 ohms when measuring from that outside lug to the middle lug. Switch to the other outside lug and you will get 250k ohms. The opposite will happen when you turn the pot in the other direction. When turning to pot and measuring from the outside lug and the middle, the reading should be gradual. If the readings go high or open and back to normal, the pot is either dirty or defective. One thing to remember is the total ohms of the pot could have a tolerance of plus or minus of up to 20%. Don't be alarmed if your 250k pot isn't exactly 250k unless it is off a lot.
To test a capacitor, you need a meter that will measure capacitance. It has been years but I don't remember capacitors having any measurable resistance and is not a proper way to test them.
Your second tech took seperate readings of the 2 pickups and found one much lower than the other. Coil windings shorting out to each other.
FunkyKikuchiyo
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New EnglandMay 12th, 2012 05:32 AM Edit Profile Print Topic Search
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Pickups will sometimes read okay on a DC multimeter but not perform properly. This is because a break will sometimes have a bit of capacitance across and still pass the signal for the meter. Sometimes you just need to have enough confidence in your wiring abilities and install it to find out.
An LCR meter can be much better at detecting problems before a regular multimeter, but at $200 it is a bit cost prohibitive for a hobbyist.
uncle stack-knob
Contributing Member
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united kingdomMay 12th, 2012 01:35 PM Edit Profile Print Topic Search
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You are talking of a single coil precision pickup, then simply connect the hot lead to the hot meter lead and the ground lead to the ground meter lead.
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