High value capacitor between Hot and Neutral at AC inlet?

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diymixer

Member
2010-06-05 5:28 pm
hey all-

I was dissecting my old Laserdisc player for parts when I saw a massive 200 uF 200V electrolytic connecting Active and Neutral right after the connection between the AC plug and the power supply board. What is the capacitor for and is it a good idea to implement it into a mixer's power supply?
 
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If it was 200uF it would be about a as big as small soft drink can for 120VAC operation, it would not be electolytic as it would explode even motor starter capacitors can only run for a short time before exploding. Motor run capacitors are fine for continuous use. FWIW I have 100 uF in a small 240V welder for partial power factor correction and I have 60uF across the 575V tap of another welder for the same reason.

Are you sure it is not a type of mains filter? I have seen these look like capacitors.

If it was a capacitor connected as such it would draw 9A with a 120V 60Hz supply.

Alternatively there might be a bridge rectifier hiding in there somewhere to get a DC supply for an SMPS.
 

diymixer

Member
2010-06-05 5:28 pm


This is the capacitor that I took out of the power supply
 
A 200uF 200 V Electrolytic across the line and neutral? No, you are mistaken. You missed the bridge rectifier. This is the filter cap for that, and it is on the front end of a SMPS.

The biggest cap I have ever seen across the line is 2.2uF, and it was (of course) an "X" rated cap and was about 2 x 1 x 0.5 inches big.
 

diymixer

Member
2010-06-05 5:28 pm
WAIT, I looked at the PCB wrong. the 200 uF cap is in front of the rectifier, with an inductor and another 2200 uF cap. The cap between live and neutral is a non-polarized 0.1 uF 250V blue capacitor (I don't know the material, but it's blue and rectangle-shaped).

Sorry for that, everyone
 

ChrisA

Member
2008-01-08 12:22 am
hey all-

I was dissecting my old Laserdisc player for parts when I saw a massive 200 uF 200V electrolytic connecting Active and Neutral right after the connection between the AC plug and the power supply board. What is the capacitor for and is it a good idea to implement it into a mixer's power supply?

This can't be right. If you put AC into an electrolytic cap it will not last long, a few seconds I'd guess. If the cap still looks like new then there must be a rectifier someplace.
 
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