Need Help Understanding Schematic

Charsbass

New Member
I am in the process of re-capping the preamp/tone board in my Marantz 2226B and I am not sure about polarity on a couple of caps. Neither the schematic nor the board has polarity indicated and I'm not sure why. The caps in question are highlighted in the images (CE27 & CE28), are 1uf/50v and they don't have a polarity stripe either. Can anyone explain this circuit to a newbie?

20170228_101056.jpg 20170228_101120.jpg
 
I'm not familiar with the unit, so I don't know for sure, but I'd suggest that they are most likely non-polar caps in that circuit. If the schematic doesn't indicate polarity, and the original caps aren't marked with polarity, they are most likely non-polar and should be replaced with non-polar caps. I use nichicon green caps or films if space allows.
 
I second bb's advice and would put a good polypropylene film in place of it. Film capacitors can be used anytime you find a electrolytic of 4.7 and lower, without worrying about polarity.
The only time polarity comes into play is if the film is big. Then it can pick up noise through induction and you would, though testing, find out which end has the outer foil and that end goes to ground, or the previous stage, depending on how its used.
Some bigger films have a black band to id the outer foil end.

I also use a 1uf. Panasonic polyester film like
ECQV1H105JL if you can find them. They fit well and are small.

If you put your fingers around an input cap, you may hear it and know its bass- ackwards, but for the small films under 400 volts, its not nessesary to do it unless your caps are next to a strong magnetic field
John
 
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Thanks for the input, I kind of suspected these were non-polar but wanted to check with those more knowledgeable than myself. I have some 3.3uf/50V Wima films on hand that will fit, would they be okay or should I go with the original value?
 
I second bb's advice and would put a good polypropylene film in place of it. Film capacitors can be used anytime you find a electrolytic of 4.7 and lower, without worrying about polarity.
The only time polarity comes into play is if the film is big. Then it can pick up noise through induction and you would, though testing, find out which end has the outer foil and that end goes to ground, or the previous stage, depending on how its used.
Some bigger films have a black band to id the outer foil end.

I also use a 1uf. Panasonic polyester film like
ECQV1H105JL if you can find them. They fit well and are small.

If you put your fingers around an input cap, you may hear it and know its bass- ackwards, but for the small films under 400 volts, its not nessesary to do it unless your caps are next to a strong magnetic field
John

John, I've been watching a guy called Mr. Carlson's Lab and he proved that the black band can't be counted on to indicate the outer foil. He does show how to build a small devise to use with your oscilloscope to define the outer foil end. Very informative IF you have an oscilloscope, I don't.
 
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