Hy spec
Thanks for the detailed reply
No worries dayanpad- nice to have another member who says thanks and supplies info
In the above attached circuit the 115v is DC voltage from the power supply. therefore is it necessary to consider 1.414 ( Sorry for half image of the CCT)
Please advice further
Thanks in advance
About the 160V capacitor:
It is certain to be an aluminium foil, wet electrolytic type, in which case, all of the following will apply.
rons has all bases covered, but I would say that, with the info that you have supplied, the 160V replacement capacitor would be fine. There is just one caviat- under start-up conditions, there may be higher voltages on the cap, but unlikely to exceed 160V or cause a problem.
Although components have ratings, like the 160V of your replacement capacitor, the ratings are what the manufacturer can meet with a massive producttion run, sometime millions. The actual peformance of a specific component can be way better than the specification. Typically a manufacturer will achieve a below spec rate of 1% to 3%. This means that the buyer may get a below spec device right out of the box. They do not normally check each capacitor but, instead, do batch sampling. I would expect, statistically, that your replacement capacitotr will take around 200V in practice.
If you really want to be fancy, put a resistor, say 5K6, and a DC ammeter in series with the cap and put 160V DC across the circuit. Leave the cap for 10 minutes or longer. The current on the meter will probably settle down to around 100ua and should not be more than 500uA, say.
Never go near energy components, like batteries and caps, when they are an unkown quantity, and especially have your eyes protected and away from the cap. Think about the cap exploding; just a precaution, but it costs nothing to play safe.
Increase the voltage and see what the meter reads. The current should shoot up with a voltage increase as the cap charges up, but then fall back to almost nothing. When you reach 200V, with no dramatic increase in current, leave the capacitor for 30 minutes or more at 200V. If, after that time, the current has not increased notably, you will have a capacitor that will withstand 200V. On the other hand, if the current starts to grow rapidly at the quescent state, that is the limit of your capacitor's voltage withstanding. You may get short bursts of current as the capacitor reforms with increses in voltage.
The manufacturer's 200V rating will apply at some specified temperature: the higher the temperature the less voltage the cap can withstand without breaking down so, unless that area of the TV is very hot, that will be in your favour.
Another thing is that electrolytic capacitors are adaptive and form a film proportional to voltage (simplifying greatly). Any areas that will not stand a particular voltage will spark across (simplifying again) and destroy the offending foil area. This is how some capacitors are made in fact.
Large energy electrolytics have a very loose specifications for their capacitance value, typically -50% +100%, so they are not prcision devices- just blood and thunder. They will normally take quite a bit of abuse.
That's the voltage side sort of covered, but not the current side.
High energy caps have a ripple current rating. This just means the current flowing through the cap. It is limited by two factors: The foil and internal connection by instantanious current capability (think fuse) and the heating effect caused by power dissipation in the capacitor (long term) which heats up the liquid electrolyte and causes expansion and even gassing- some electro types have vents, and nearly all have blow off plugs at the end to release pressure in the event of over gassing due to excessive heat.
Capacitors will normally take massive currents for short periods, as in a conventional rectifier circuit without an inductor. The formula for the heating effect is (ripple current squared times ESR). ESR is the effective series resistance of the capacitor and is affected by various things including temperature.
Rons' method of measuring the ripple current with a DC ammeter in series with the capacitor input is, by far, the best method. But if that is not possible, you can measure the AC voltage on the capacitor, which will give you an idea of the ripple current. Use a scope, or if no scope, an AC voltmeter in series with a 100nF (say) solid capacitor. The AC voltmater must be capable of handling the the freqencies involved though.
The other aspect about ESR is that, if too high, it can actually stop the circuit from working or make it work inefficiently, especially in modern high frequency switch mode power supplies.
Electrolytic capacitors are lifed items and need to be replaced typically after 2,500hours to 5,000 hours. This time is very much reduced by high temperatures and high currents (which cause high tempersture in the can)
If your capacitor has any meaningfull markings on it, if you like, post it exactly as printed and I may be able to check specifically what the capacitor it is.
I have finished now, but one last word about safety: make sure you leave a resistor (100K say) across the cap for a few minutes to remove all the charge. It is no good just discharging a capacitor to zero volts and then removing the resistor because the voltage can recover by dialectric absorbsion, an effect that is not fully understood.
Hope you are not too bored- I have done quite a bit with capacitors for specialist applications.
Must have some breakfast now- just woken up