Filter Capacitors

[Irrigator55]

I have pioneer sx 1980 stereo receiver. Manufactured 1978-82. I have re capped all of the electrolytic capacitors except the 4 large filter caps. The old caps are marked BLACK-NEG on the side. There are no markings at the screw terminals. The new caps are marked POSITVE on the side. There is a plus mark on one screw terminal. Im not sure how to connect wiring to new caps. Help needed please.

 

[Nigel Goodwin]

If in doubt simply power it up, and measure the voltage on the capacitors.

 

[Irrigator55]

Im definitely in doubt. Is there another way to know without risking damage to unit. This is a vintage receiver and expensive. Not easily replaced.

 

[Nigel Goodwin]

Why would powering it on damage it?, it's quite probably the large capacitors are perfectly fine, and don't need changing anyway.

But if you don't want to power it, simply follow the connections back to the bridge rectifier - assuming this is a split power (+ve and -ve) the positives of one pair of caps will go to the positive of the bridge, and the negatives of the other two will go the negative of the bridge. All four other connections should join together and go to ground.

 

[dr pepper]

If the stereo is untouched and original you could power it on, measure the voltage on the original caps with a meter & mark the polarity on the wires with some tape, then fit the new ones observing said polarity.

 

[sagor1]

Wiring the new caps is basically the "same polarity". That is, old cap shows -VE, new cap shows +VE, then the unmarked terminal of the new cap is -VE. Most caps only mark one terminal, and the other is simply the opposite. Two terminal caps that are marked either - or + on one terminal, is just to tell which is which. The unmarked terminal is the opposite.

 

[Irrigator55]

Thanx for reply. I understand this. My concern is that the old caps have no markings except on the side. Print reads neg-black but does not specify which terminal is + or _

 

[rjenkinsgb]

Look at the black dot on the top of the riveted point that holds the terminal solder pins - it's on the left hand terminal in the photo with the pins upwards.

That's the negative terminal identification.

 

[Irrigator55]

Thank you. Much appreciated.

 

[NsrMagazin]

The new caps show which side has the positive pin.

This might help you.
https://www.electro-tech-online.com/threads/negative-capacitors.94474/

The black pin is the negative pin.
I think this is for your system:
https://marantzhallo-fi.blogspot.com/2018/02/a-tacussis-sansui-au-7900-integrated.html