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Joined:
April 2003
Posts: 608
Location: Caribou, ME | A guy emailed with a question about the preamp in his Ovation. I accidentally deleted the original email so I don't have the particulars but apparently these little transformers became unsoldered and he doesn't know how they go back in. They have different part numbers; both say E19-55 but one says D7, the other D10. So he needs to know which one goes in which position and also the orientation. Does anyone have an old preamp like this they could post a pic of? Thanks.
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Joined:
October 2005
Posts: 4055
Location: Utah | It appears there are only 2 leads coming out of each one, right? If so they are not transformers they are inductors. The orientation will not matter.
I don't recognize the D7, D10, or E19-55 nomenclature. If your friend has a multimeter he could try measuring the DC resistance of each to see if there is a substantial difference. The resistance will indicate the length of wire in the coil, so if the resistance is close it means the coils are wound with the same number of turns and the same gauge of wire, and thus the inductance is the same. If they are within about 10%-20% I would call them identical. |
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Joined:
April 2003
Posts: 608
Location: Caribou, ME | Cool, I'll pass that along. Hopefully he has access to an ohmmeter. Thanks. |
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Joined:
January 2006
Posts: 1122
Location: NW Washington State | I think this might be the schematic for the preamp. 
The inductors in this schematic are the same with different capacitors in parallel- your version may vary. Looks like it could be a filter to cut the midrange. I'd replace the 5uf electrolytic capacitors before reinstalling the preamp. Metalized polypropylene capacitors might be an improvement but are probably too big. -Steve W.
Edited by numbfingers 2013-12-29 11:16 PM
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Preamp help needed