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Joined:
August 2004
Posts: 604
Location: Tampa, FL | Joe,
You might try emailing BruDev. He helped me out (Twice) when I was trying to help a fellow OFC'er.
Somethings to consider:
I don't think the stacked pots are identical either in value or taper. seems to me one was 2X the value of the other and one was linear and the other was logarithmic.
I can say that the carbon flaking off the substrate is what I found to be the problem with the Tone pot I was messing with. It seems to be a recurring mode of failure. |
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Joined:
January 2003
Posts: 1498
Location: San Bernardino, California | I think what happens is that the sponge rubber in the battery compartment decomposes and gets into the pot.
Lift the 4 tabs on the top edges. Remove the threaded piece and the top wafer. Do the same with a 500K linear CTS pot. Put the 500k wafer on the tone pot. Put the threaded piece back on. Bend the tabs back down.
The treble/bass won't be the same but, it's real close. You can try different values for the treble bypass if you want.
Or replace the gate resister on the following stage with a trimmer. (750K?) And use that to dial in the treble/bass balance. |
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Joined:
January 2003
Posts: 1498
Location: San Bernardino, California | PS You'll need to lengthen the leads on the 500K wafer. |
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Joined:
December 2008
Posts: 11
Location: Enon, OH | Hey BruDev - I didn't even see your posts until recently, I'm apparently not smart enough to go to the second page! I ended up doing exactly what you describe, except that I used a 500k audio-taper wafer (because I had one). It worked great and the sweep is actually pretty darn close to the original. Thanks for the advice! This place is great, I'm so glad there's a whole slew of you guys who love these guitars. By the way, SUPER nice job on the schematics, totally cleared up what the tone pot values are supposed to be.
Kind regards,
Crazy Joe |
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Joined:
January 2003
Posts: 1498
Location: San Bernardino, California | Great.
I suspect that you could use a 1 Meg pot and put a parallel resister across it, and get even closer.
I've seen a few other variations of the preamps, but the changes are so minor that I didn't put in the effort of pulling the circuit boards from the guitar to draw a schematic. |
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Joined:
December 2003
Posts: 13987
Location: Upper Left USA | I am resurfacing this post for two reasons:
A) Andrew in Oz asked about a Breadweiner schematic
B) You Electronical people are awesome! |
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Joined:
January 2006
Posts: 1118
Location: NW Washington State | I think that BruDev is The Expert on this stuff.
Andrew in Oz sent me an email and I replied with the usual info...
Here's a link to a page that explains how the preamp works: http://www.ovationtribute.com/Catalogues/Breadwinner%20Settings%20M...
It's not worthwhile for the average person to try to make an exact copy of the original preamps. They used some custom-made parts that aren't available anywhere I've looked. But here are some schematics from OFC member BruDev:
http://www.ovationfanclub.com/photos/BruDev_63029_c-2.jpg
http://www.ovationfanclub.com/photos/BruDev_63084_c-3.jpg
http://www.ovationfanclub.com/photos/BruDev_63139_d.jpg
http://www.ovationfanclub.com/photos/BruDev_63183_e.jpg
http://www.ovationfanclub.com/photos/BruDev_63233_f.jpg
The last two schematics on this page are for Breadwinners: http://www.doremi.co.uk/breadwinner/circuits.html
The second one from the top is for a UKII and was posted on the Breadwinner page by mistake.
If you want to duplicate the action of the Breadwinner preamp, you need an active bass/treble "tilt" control on a single knob, a volume boost ganged to the pickup switch when both pickups are selected in parallel and out of phase, and a midrange notch filter switch with volume boost. I can imagine several ways to get close to this but don't have any specific suggestions. It would be pretty easy to build a preamp with conventional volume and tone controls and maybe a treble boost in place of the notch filter switch. Or you could try one of the Artec preamps that are commonly available on eBay.
-Steve W. |
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Breadwinner tone pot - please help a brother out!
