Compaq TFT450 No Power

[news.pipex.net]

Hi,

I have a compaq TFT450 lcd monitor which won't power up. The input fuses
on the 5v and 12v inputs are fine. After the each fuse there is a 470 micro
farad capacitor. I have a multi-meter but I am not too sure on how to test
the capacitors ?

If anyone has any pointers, hints or tips on what to look for please let
me know.

Regards

Dave K.
[email protected]

 

[Peter van Merkerk]

I have a compaq TFT450 lcd monitor which won't power up. The input

fuses on the 5v and 12v inputs are fine. After the each fuse there is
a 470 micro farad capacitor. I have a multi-meter but I am not too
sure on how to test the capacitors ?

To test the capacitors you will need an ESR meter. It is very well possible
that one or more electrolytic capacitors are bad. Coincedently I repaired a
Compaq TFT screen yesterday (randomly flashing lines); while tracking down
the cause of the problem I did notice that many of the SMD caps did have a
poor ESR. In this case the problem was caused by a bad electrolytic cap
near the power input.

 

[Peter van Merkerk]

To test the capacitors you will need an ESR meter.

An alternative for using an ESR meter is to use a oscilloscope to watch the
signal over the capacitor when the device is powered on. If the capacitor
is good you should see no or only a very small signal.

 

[news.pipex.net]

Hi Peter,

I think that its the two surface mount capacitors near the fuse
terminals. Is it simply the case of removing them by de-soldering the two
contact points on either side of the caps ?

Regards

Dave K.