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Which way does it go? - Printable Version

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Which way does it go? - raydog - 04-28-2012

While waiting for a new transformer to show up, a previous thread caught my attention concerning the polarity of an electrolytic. I recently recapped my #18 but noticed I may have installed cap #55 incorrect. Could someone verify that positive on the cap should go to chassis ground and not the other way around? http://www.theoldradiofixerupperguy.com/pdf/Philco/model18.pdf

Thanks Don

RE: Which way does it go? - morzh - 04-28-2012

I thik Gnd should be positive. Your centertap is the rectifier's negative and is the most negative point in the whole pwer setup, the rest is positive relative to it, including Gnd that is onnected by a resistor.

RE: Which way does it go? - rghines1 - 04-28-2012


Agree with morzh. Positive end of cap 55 connects to chassis ground.

RE: Which way does it go? - raydog - 04-29-2012

Thanks guys. I was tossing this back and forth in my head when I was doing the recap. I had a 50/50 shot at it and I chose the wrong one. Will get it fixed and another problem solved. Thanks

RE: Which way does it go? - morzh - 04-29-2012

I thought from your post that you did connect positive to GND?

Here's how you can think of it: Unless you have another source of negative, the most negative point in your whole circuit is the negative of your rectifier. This is as negative as it will get. Now, the cap is decoupling the low value resistor's (this is usually the big powerful one with taps) leftmost point, the GND, towards the neg. of the rectifier. Whatever current flows through it, being sunk to the negative, it will create a positive potential on its other end, the GND, meaning that whatever it is there, it is positive towards the Rect. Negative.

Hence, PLUS of the cap is on the GND.

So, your