COM-120B Power Supply polarity of the capacitors !!

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Audiotron
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COM-120B Power Supply polarity of the capacitors !!

Post by Audiotron »

It is with a COM-120B missing some capacitors I believe are 120UF but someone has some photo so I can identify their polarity on the board ??

image link Power Supply : http://ap.imagensbrasil.org/image/dV1lC8


Thanks a lot
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kcbooboo
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Re: COM-120B Power Supply polarity of the capacitors !!

Post by kcbooboo »

Usually there's a white or silver line along the side that marks the negative lead of the cap. In the photo, this line wraps over the top of the cap and is on the side opposite from those yellow connectors.

If this is a power supply board, there are probably negative power supplies where the positive terminal of the cap is grounded, not the negative terminal, so watch out for those.

The board may have + silk-screened on the board, or a dot, or a different shaped solder pad, but not always.

Bob M.
Audiotron
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Re: COM-120B Power Supply polarity of the capacitors !!

Post by Audiotron »

Hi Bob ,

unfortunately we do not have screen printing on the board, and are missing the capacitors on the board which would be easier to identify the polarity, with respect to the voltage line some I believe I already know the position but the corner are connected between different points of GND or something different feeding meshes which leaves it confusing to know the polarity
an image of such a source with capacitors in place or even the diagram would be interesting
LZ1IM
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What radios do you own?: Collins 51S1, Maxon HR146

Re: COM-120B Power Supply polarity of the capacitors !!

Post by LZ1IM »

Hi, Audiotron,
Missed capacitor is C13, PCB is Switcher, + is on the right at Picture, Value is 120 uF/50V.
It is Filter Capacitor of -10.5V. Hope it is useful for You.
LZ1IM
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Posts: 11
Joined: Mon Nov 07, 2016 4:34 am
What radios do you own?: Collins 51S1, Maxon HR146

Re: COM-120B Power Supply polarity of the capacitors !!

Post by LZ1IM »

Ah, Missed at the Left in Picture is C38 120uf/50V, Filter of +13V Unregulated, and + of C38 is at the Left.
For C13 all is as in the Previous Post.
LZ1IM
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