Project - LCD Monitor Light Issue

S

SudburyOntario

Gawd
Joined
May 5, 2008
Messages
575
I am in the current situation where as I have an lcd monitor made by ProView 20" tv with pc input.

The lights turn on and than off in a mear second, yet upon changing the input.. the backlight appears on again for another second. I do not know if this would be related to the transformer, or possably something else.

I own a Fluke Multimeter, and Currently all capacitors are perfect.

Thank you [H] in advanced.
 
It sounds to me like the transistors for the backlight have died, and the overcurrent protection is kicking in. I have a 17" Dell LCD with the same problem. If you can figure out which ones are dead, and replace them, you might be able to get it up and running again.
 
Would that be the most likely fault ? I have tested for current output and they seem to operate.. altho I do not know How much current should be flowing through :eek:
 
The backlights (which I'm assuming are the problem) run off high voltage and relatively low current. The transistors could have gone bad (and you usually have to remove them from the circuit to test adequately), or the transformers. Heck, it might even just be some corrosion on the connectors. I've seen all three.
 
If I was to replace a capacitor.. what are the rules ? Same uf rating however if said voltage is 25v can I go with a higher voltage or a lower voltage ? what happens if I replaced a 470uf 50v with a 470uf 20v ?
 
*Bang*

Don't replace with lower voltage units ever.

I just replaced 2 blown caps in my Viewsonic vx922......they were 10v units , I've put in 16v units of the same value.Works like new .

:D
 
SudburyOntario said:
If I was to replace a capacitor.. what are the rules ? Same uf rating however if said voltage is 25v can I go with a higher voltage or a lower voltage ? what happens if I replaced a 470uf 50v with a 470uf 20v ?
Click to expand...

In your example the circuit would probably malfunction, ranging from poor filtering (lots of noise in signal) due to a smaller cap, to the cap actually blowing up due to overvoltage.

Voltage should always be the same and sometimes higher depending on the application (filtering, power). The (u)F rating has similar rules. In power applications higher ratings shouldn't hurt.
 
Typically, capacitor replacement is "same capacitance, same or higher voltage." A lot of times, using a higher capacitance is also ok (and sometimes even beneficial), but without a full schematic, you can't know for sure.
 
You must log in or register to reply here.
Back
Top