Can anyone help me determine what I have here?

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Re: Can anyone help me determine what I have here?

Postby Greg Robinson » Wed Mar 21, 2012 6:30 pm

Yes, the 10k master volume is post-preamp. It would still work with 250k though.
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Re: Can anyone help me determine what I have here?

Postby Kurt Veltman » Wed Mar 21, 2012 9:33 pm

It works! The only problem I see at this point is a crackle when I turn the blend knob. On a stacked pot, is the upper the treble and the lower the bass? I don't hear alot of difference when I turn them.
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Re: Can anyone help me determine what I have here?

Postby Greg Robinson » Thu Mar 22, 2012 5:14 am

Great news Kurt! Glad we got you up and running.
Yes, usually if stacked, treble will be top, bass will be bottom.
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Re: Can anyone help me determine what I have here?

Postby Kurt Veltman » Thu Mar 22, 2012 1:31 pm

Any common reason the blend knob would crackle? Also, I know you are supposed to ground the bridge, but I haven't done it yet. What problems would I be having by not grounding it?
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Re: Can anyone help me determine what I have here?

Postby Jim McConkey » Thu Mar 22, 2012 6:27 pm

Crackling is usually caused by dirt and oxidation in an old pot. You can try just turning the pot back and forth from end to end a whole bunch of times, and that often eases the problem, at least temporarily. Radio Shack used to sell spray pot cleaner, but I don't know if they carry it any more. If the pot continues to be noisy, I would just replace it with one of the same type. Also check the solder joints on that pot. Loose connections can cause the same problem.
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Re: Can anyone help me determine what I have here?

Postby Kurt Veltman » Fri Mar 23, 2012 8:51 am

Jim, these are brand new pots, so considering that and my soldering ability, I'm betting on bad solder joints. Those I have seen solder that know how to do it (Mark Swanson) make it look so simple. Some of them go very well, some I can't get to work to save my life.
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Re: Can anyone help me determine what I have here?

Postby David King » Sat Mar 24, 2012 12:41 pm

Crackling pots is also an indication of a DC offset or of ground leakage in a floating ground system. I'm not sure why that would be happening to you now but I'm pretty sure that's the problem if the pots are new as you say. I have a bag of 50 or so of those baselines blend pots, I won't be using them.

Treble and bass not functioning is a further indication of something not wired up correctly. Check battery polarity, red wire to +9 or +18V. Black wire from battery clip to the ring lug of the output jack. Are the input and output wires reversed?
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Re: Can anyone help me determine what I have here?

Postby Kurt Veltman » Fri Mar 30, 2012 10:32 am

For those who have been helping me try to figure this thing out, I thought I give you an update. I took this bass to a somewhat local show last weekend, bringing with me the extra pots I had and my soldering iron in case I had time to check into the crackling pot. Another issue I was hoping to resolve was a blend pot that didn't turn smoothly. When I took the back off, I was happy to see that a bare ground wire had found it's way into the gap between the body of the blend pot and the disk that turns with the knob, slightly separated from the pot body. At first I though this solved both problems, but I eventually had problems with the volume pot again. I am tempted to make a fixture with holes for the pots in the same location as they are in the instrument, so I can solder everything in its place, remove it from the fixture, and place it in as a unit. This might limit flexibility once it's in (depending on how much extra wire I leave between pots, etc.) but should clean things up, make it easier to get good solders and limit the amount of flexing and stress on the solder joints, hopefully keeping them intact.

Fortunately, it played fine for my bass player friend who happened to be in town from across the state. Everyone seemed impressed with the basses, in large part due to the help I have received from people on here. Thank you all very much.
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Re: Can anyone help me determine what I have here?

Postby Greg Robinson » Fri Mar 30, 2012 11:18 am

Great to hear Kurt!
When the stray wire got into the pot it may have scratched the trace or lifted the wiper, so you'd be best to replace it if it's scratchy now.

On your plan to use a template and install as a unit, I do this frequently with more complex wiring jobs, helps prevent problems and allows you to do a much more professional looking job without the cramped space of the cavity.

Really glad we were able to help you out with this.
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Re: Can anyone help me determine what I have here?

Postby David King » Sat Mar 31, 2012 1:10 am

The blend pot has that spinning disc on the back with the rectangular hole for the center detent mechanism. It has nothing to do with the wiper or trace. I still think the crackling may be an electrical/wiring problem, not necessarily a bad pot. I used to tame wires by shortening them but in the long run I've decided that this is not a productive use of my time. Most bass preamps get upgraded long before they reach the end of their useful life. It's a technology that's constantly changing that we try to meld into an instrument that's likely to to last several lifetimes. As preamps migrate to another, lesser instrument in a few years someone may be glad to have all the wire length you can afford them.
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