Cap volts?

[ivtec]

Hi guys i have here a Lcd pc monitor and it has a 100farads 450v in the power sup, that is dry can i use 200v instead of the 450?

[Majestyk]

Re: Cap volts?

Don't!
You can use 450V DC or more.
The capacity is probably uF not F - the unit would have a remarkable size otherwise.

[ivtec]

Re: Cap volts?

Don't!
You can use 450V DC or more.
The capacity is probably uF not F - the unit would have a remarkable size otherwise.

Thanks,true is 100uf450v, i have many caps on my scrap but none with that volts.

[mariushm]

Re: Cap volts?

If the monitor doesn't have active power factor correction, the AC voltage gets rectified so you will have 120v x 1.414 = 170 volts. You may get more than 120v at the socket, you may get less, so the rectified voltage may get close to 180-185v. So using a capacitor rated for 200v would maybe work but it's awfully close to 200v, and I wouldn't recommend it.

As I said, IF there's no active pfc. In this case, it's possible they may have used a 450v rated capacitor so that they won't change the power supply in countries with voltages that can be 240v +/- a few percents. In those countries you get 240x1.414 = 340+ volts, so you need at least a 420v rated capacitor.

BUT, if the monitor uses active pfc, the active pfc circuitry will boost the rectified voltage to some value, which normally is about 380v-400v or maybe even more. So you'd need to use a 450v rated capacitor.

Most monitors will work at high voltage, it's just hard to sell monitors without due to regulations for efficiency and low standby power and so on.

[ivtec]

Re: Cap volts?

If the monitor doesn't have active power factor correction, the AC voltage gets rectified so you will have 120v x 1.414 = 170 volts. You may get more than 120v at the socket, you may get less, so the rectified voltage may get close to 180-185v. So using a capacitor rated for 200v would maybe work but it's awfully close to 200v, and I wouldn't recommend it.

As I said, IF there's no active pfc. In this case, it's possible they may have used a 450v rated capacitor so that they won't change the power supply in countries with voltages that can be 240v +/- a few percents. In those countries you get 240x1.414 = 340+ volts, so you need at least a 420v rated capacitor.

BUT, if the monitor uses active pfc, the active pfc circuitry will boost the rectified voltage to some value, which normally is about 380v-400v or maybe even more. So you'd need to use a 450v rated capacitor.

Most monitors will work at high voltage, it's just hard to sell monitors without due to regulations for efficiency and low standby power and so on.

Thanks Bro for that Very good Explanation,i'm going to lieve this lcd repair alone, i have a couple more monitors , besides who ever threw it out cut both the video cord and power cord, not worth it the trouble,maybe i can salvage the panel lcd,i have a lenovo lcd monitor same size panel lcd

[lexwalker]

Re: Cap volts?

If the monitor doesn't have active power factor correction, the AC voltage gets rectified so you will have 120v x 1.414 = 170 volts. You may get more than 120v at the socket, you may get less, so the rectified voltage may get close to 180-185v. So using a capacitor rated for 200v would maybe work but it's awfully close to 200v, and I wouldn't recommend it.

As I said, IF there's no active pfc. In this case, it's possible they may have used a 450v rated capacitor so that they won't change the power supply in countries with voltages that can be 240v +/- a few percents. In those countries you get 240x1.414 = 340+ volts, so you need at least a 420v rated capacitor.

BUT, if the monitor uses active pfc, the active pfc circuitry will boost the rectified voltage to some value, which normally is about 380v-400v or maybe even more. So you'd need to use a 450v rated capacitor.

Most monitors will work at high voltage, it's just hard to sell monitors without due to regulations for efficiency and low standby power and so on.

Sometimes I've used 400V ones, when I don't have any spares left. But only for monitors that do not have PFC. Otherwise I will stick to 450V...

[Majestyk]

Re: Cap volts?

I would recommend to stay on the safe side (450Vor more). You never know - maybe some day the TV is taken to any country (for example in south america) where there is a mains voltage of 220V. Since there´s probably a rating of 100-240V printed on the Label someone plugs it in and -
"boooom"

[lexwalker]

Re: Cap volts?

I would recommend to stay on the safe side (450Vor more). You never know - maybe some day the TV is taken to any country (for example in south america) where there is a mains voltage of 220V. Since there´s probably a rating of 100-240V printed on the Label someone plugs it in and -
"boooom"

My country uses 230VAC for the mains. Already used 400V capacitors for quite a number of repairs already, and none came back for second round of repairs...

[Majestyk]

Re: Cap volts?

And none of them ever will - I´m sure.

I referred to the possibility to use 200V as mentioned in post #1 and #4

[lexwalker]

Re: Cap volts?

And none of them ever will - I´m sure.

I referred to the possibility to use 200V as mentioned in post #1 and #4

Majority of LCD monitor power supplies are universal, can accept 110VAC to 240VAC mains input. Thus usually 400V would be the safe minimum, in most cases. Although I would not recommend 200V though...

[ivtec]

Re: Cap volts?

Thanks guys: If i understand i can use a 200V 100uf cap as long i use 120v power?

[mariushm]

Re: Cap volts?

Short answer is that IT DEPENDS. Most often you can't.

It depends on how the power supply is built.

If the power supply has a Active PFC circuit, then no, the voltage will be boosted by this Active PFC circuit to about 380-400 volts so you need a capacitor rated for at least that voltage, therefore 450v rated capacitors are used.

The majority of power supplies will be like this.

Just order some 450v rated capacitors from Digikey or Mouser or Newark and forget about shortcuts.

Most monitor power supplies use capacitors in the range of 100-150uF - you can generally go a bit more or a bit less in capacitance (ex. use a 82 uF instead of 100uF, or 120uF instead of 150uF, or use 120uF instead of 100uF) so you could just get a few capacitor sizes and install the closest one you have when needed.