Repair lcd with bigger caps

[Davi.p]

Hi, i'm new here and i'm from Italy so be patient with language..
Few days ago i had the luck to go to a workplace and recover a wonderful
20" wide lcd mon. from Philips, the man says 'it's burnt, you can get it',
i opened it and there was 2 caps bulged that i replaced with 2 other grabbed
from a pc mo.bo., i had only one value so i decided to change that 1000nF with 1500uF ones hoping well, The monitor is tested for 30 min. and goes well.. but theese thays i'm discussing in italian newsgroups if is safe to change with this greater value (same volt), many guys says no, but i'm discussing the why, i don't want to reopen it (is difficult) if there is no reason,
one man says them will have shorter life than original, but another said for he companies puts undersized caps in hope them will break one day, after warranty period, so users go to buy anther one, in this optic a greater value seems ok, the caps are on the psu near the output conn. , another says them a output filter/rectifier and with higher val. it grow the voltage that
enters in voltage regulators and need more heat sinking, to you the question..
hope it's interesting...

[shadow]

Re: Repair lcd with bigger caps

It is hard to say definitely what effect greater capacitance will have in a circuit without patience and a circuit diagram. In a digital circuit, I believe a capacitance that is slightly higher than what was put in there before hand is generally going to work alright.

Remember that electrolytic capacitors generally have a 20% tolerance. Therefore your 1000uF capacitor when brand new could have been in fact 1200uF.

Others on here have a lot of experience and probably can answer your questions better than me. However I will give it a go.

1. Higher capacitance may shorten life
That is difficult to say without having a fair bit of experience and without studying the circuit.

2. Companies put under sized capacitors in their products
Unfortunately many companies (mainly cheap Chinese brands but not only) put inferior capacitors into their products. I do not think they go under capacitance because the price difference between for example a 1000uF and a 1500uF capacitor is next to nothing. Generally they use cheap capacitors with exaggerated specifications and possibly are also made from inferior materials and inferior processes.

3. Higher capacitance causes higher voltages for the voltage regulators and other electronics in a power supply
This is definitely false. A capacitor charges itself upto the source voltage. It is not possible for the voltage across a capacitor to increase magically just because it has a greater capacitance.

I hope I have answered at least some of your questions.

[Davi.p]

Re: Repair lcd with bigger caps

for the point 3. he means that the capacitor receives a not rectified voltage from earlier components , it charges up to the peak voltage and the output because of higher cap. value has a mid voltage higher than original to the regulator designed to
have a certain medium voltage .. i report his words.. don't know if has sense..