LCD inverter output capacitor values?

[113]

lcd inverter capacitor

Inverter pcb for backlight in an LCD monitor model PV-1710.

One of the output capacitors has burnt up. It is on the output of the board (feeding the tube) and is labeled 33J 3Kv which I assume is 33pF at 3000v.
Can anyone confirm this value? Farnell says 33J is 33nF but I believe the J is tolerance fo 5%.

Is the 33pF value critical?

What will happen if I use a larger value, e.g. 1.2nF ?

 

[pranam77]

lcd capacitors

Dear friend, The values of the output capacitors are pre calculated to give pure output without distortion to the tube. Changing the value will result in blackening the tube ends thereby drastically reducing the life. You need to replace with the same value with same voltage. I am not sure about the value you have given. Because if we asume 33J as 33 PF it is too low for the frequency on which the tube operates. I guess (Not sure) it should be 3n3 which will operate between 25Khz to 35Khz. you may get better replies from other friends in this regard. Good luck

 

[113]

lcd inverter capacitors

Thank you for such a quick response!

I took a look at a previous post which shows a schematic for the ALPS LCD1830 inverter. The output circuit looks the same as mine, but without output capacitor values shown.

The two capacitors get their pulse from the same transformer pin, then feed the tube. A third wire to the tube looks earthy.

I just can't figure out how the tube connects.
Is there a schematic of how the tube connects?

p.s. one of the tubes is already blackened (I have two identical monitors exactly the same, top left is dark).

 

[engineeralee]

33j 3kv capacitor

I dont know much about ur prob