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Old 22nd March 2013, 02:25 AM   #1
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Default Mystery Capacitor Polarity?!

Rather that consult with a tech somewhere ($) I'll give our forum members a try at solving a mystery for me regarding capacitor polarity. *please refer to the attached photo and schematic* I am finishing up on a 5-channel recap project and cannot identify the polarity of the lone capacitor on the PC board. The cap jacket has no indication of a negative pole. According to the parts list it is indeed a polar capacitor. The cap in question is C14 on the schematic.
In the photo the cap is the small guy located directly under the green wire. Now, in relation to the photo, would the negative pole be situated to the top or the bottom of the photo? I hope my explanation and docs are clear enough! Thnx, Jon

I oriented the photo and schematic so that the 5-pin connector is located on the left of both.

B&K 7250 II
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File Type: jpg schematic.jpg (182.2 KB, 66 views)
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Old 22nd March 2013, 02:36 AM   #2
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C14 in the schematic, the top flat part should be positive and the curved part towards the bottom is negative.
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Old 22nd March 2013, 02:37 AM   #3
Johno is offline Johno  Australia
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Trace the pcb tracks to see which end is connected to Q9 and which end goes to Q12.

Last edited by Johno; 22nd March 2013 at 02:38 AM. Reason: correction
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Old 22nd March 2013, 02:39 AM   #4
Enzo is offline Enzo  United States
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If a cap has a polarity, then it must be installed as drawn in the schematic. But the cap doesn't NEED to have polarity. An non-polar/bipolar cap is fine too, even a film cap would work, though it would be way too large fo fit. If teh existing cap is non-polar, it won;lt have a polarity marking, and as such could go in either way.


If you want to know which end is which, the + end would be the end wired to the trim pot. The negative end would be the end wired to Q12 and R10. Ah, I see the note that R10 is a jumper, putting the cap parallel the trimmer. In that case the + end of the cap is the end with continuity to Q9 and the negative to Q12.
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Old 22nd March 2013, 02:41 AM   #5
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Hi,
The schematic it is hard to read but if I am right the capacitor C14 it is a 10uf 25 volts. The positive side goes to the wiper or middle connection of the variable resistor R2. You need to follow the printed circuit run and look for the connection for the variable resistor R2 wiper or the middle connector of the resistor.
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Old 22nd March 2013, 02:55 AM   #6
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Sounds good. Thanks. ..But then what? Negative to Q9 or Q12 ....? Positive to Q9 or 12?
It seems I'm getting warmer!! Jon

***In responce to Johno's advice**
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Old 22nd March 2013, 04:02 AM   #7
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That is clearly shown on the schematic. + to Q9, - to Q12.
That 'lytic will have a polarity mark, or maybe a BP on the label for bipolar.
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Old 22nd March 2013, 04:08 AM   #8
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HI,
If the capacitor it is bipolar then the polarity does not matter. Just solder the capacitor in any direction.
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