High value capacitor between Hot and Neutral at AC inlet?

[diymixer]

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?

 

[neutron7]

DO NOT DO THAT!

there are special grade capacitors for AC, and you must use those. are you sure it is not 200nf? i think 200uF would explode.

check more closely, i cant see them doing that.

 

[diymixer]

I'm positive that it's 200 uF; it's been in the player for the past 15 years and it still appears brand new

 

[SY]

If there's 200uF of electrolytic across the line, what you have is an explosion. So... either it's not 200uF or it's not across the line.

 

[Cristi]

Motor starter capacitor power factor correction, in the old fashion. anyway, 200uF should take half on the space inside the case.

 

[metalsculptor]

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.

 

[AndrewT]

no knowledge is dangerous.

Go and get help.

 

[analog_sa]

I'm positive that it's 200 uF; it's been in the player for the past 15 years and it still appears brand new

It is so unpolite to argue with people. Why discourage him if he is so positive? Nevermind the cap is after a rectifier in an SMPS - how different can this be to what he's saying

 

[pjp]

were SMPSes in use in the days when LaserDisc players were being built ? I thought all of those day's electronics had linear power supplies.

 

[wwenze]

"right after the connection between the AC plug and the power supply board"

I interpret it as the capacitor is on the power supply board, and after a rectifier.

 

[Cristi]

Wouldn't be more easy to tell us the brand/model and google-it to find about that cap ? or at least some pictures ?

 

[diymixer]

"right after the connection between the AC plug and the power supply board"

I interpret it as the capacitor is on the power supply board, and after a rectifier.

The capacitor is actually before the transformer primaries

 

[hags]

Post a picture.

 

[diymixer]

This is the capacitor that I took out of the power supply

 

[SY]

Difficult to see it on your hard drive.

 

[macboy]

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.

 

[AndrewT]

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.

J. Curl recommends upto 10uF across the mains Live to Neutral for RF attenuation and a small amount of harmonic reduction.

 

[diymixer]

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

 

[AndrewT]

Hi,
check that blue boxed 0.1uF.
Has it got X1 or X2 printed on it?
Designed especially to go from Mains Live to Mains Neutral.

 

[ChrisA]

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.