Replaced monitor capacitors, still not working

[Bobofwoggle]

I've got another broken monitor. Well, the same one as last time I was here, but whatever. Basically, it wouldn't power on so I checked for bulging caps, one was, I ordered replacements on Digikey and just now replaced them, but the monitor still doesn't work. The power light doesn't come on, the screen doesn't come on, nothing. I made sure the polarities on the caps are all correct and that I didn't screw up the soldering anywhere, and I just can not seem to find what's wrong. I'm worried I either got faulty caps from digikey or broke them somewhere in the process. Is there any way to test this, or does anybody have any suggestions about what else the problem might be?

 

[ffg7]

does the monitor use a regular power cord or a power adapter which will tell us if you have 1 or 2 circuit boards in it? did you use the same value capacitors as what the old caps were as in 1000uf 25v?

 

[Bobofwoggle]

It uses a regular power cord, has 2 boards (power and output), and I made absolutely certain before ordering replacements and double-checked before putting the replacements in that the values were the same as the originals.

If it helps any, prior to replacing the caps, the monitor would turn on if heated with a blowdryer for a few minutes beforehand, now it does not.

 

[ffg7]

which board did you use the blow dryer on as in power board or video controller as that sounds like a cold solder joint? which board did you replace the caps?

 

[Bobofwoggle]

Both the blow dryer and the cap replacement were done on the power board.

 

[ffg7]

re-solder all the solder points on the power board. had to do that on my step father's radio shack model 4 computer floppy controller card about 30yrs ago.

 

[Bobofwoggle]

Finished reflowing all the joints on the board, and the second I plug it in sparks fly out of the board's ac input. Fairly certain the board's ruined now, so that's nice.

 

[ffg7]

it appears you must have bridged 2 or more solder points. where you using a solder gun or solder iron\pencil? what is the make & model# of the monitor?

 

[Bobofwoggle]

I use a pencil style weller soldering iron, one that just plugs straight into the wall with no base station. The monitor is an LG flatron 194wtx-bf, and the power board it uses is marked 68709d0012c.

I'm fairly certain what happened is I shorted some components on the metal chassis that holds both of the boards onto the panel as I was plugging it in, as I can't see any solder or leads where they don't belong, and the neutral pin joint on the AC in, as well as one of the legs of the switchmode transformer, are charred black.

 

[ffg7]

do you want to try again to power up the monitor?
power boards http://www.ebay.com/sch/i.html?_odkw=LG+flatron+194wtx-bf+power+board&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.XLG+194wtx-bf+power+board.TRS0&_nkw=LG+194wtx-bf+power+board&_sacat=0
logic board http://www.ebay.com/sch/i.html?_odkw=LG+194wtx-bf+video+board&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.XLG+194wtx-bf+main+board.TRS0&_nkw=LG+194wtx-bf+main+board&_sacat=0

 

[Bobofwoggle]

Ended up taking the power board from another (similarly nonfunctioning) monitor, replacing the caps on that with the replacements I got from digikey. It works now.

 

[ffg7]

good!! did that with my 19" Samsung Frankenstein monitor but not just the power board but also the video controller board that also had dvi instead of vga as on the old board. had to modify the bezel front to accept the buttons board that came with the new video controller board.