Philips 190S ten mins to black

[SBlackfoot]

Please forgive me, this is my first tech post here and it'll probably be a mess. You guys like detail, right?

Long story short (dontcha love stories that start like that?), I have two Philips 190S LCD's that are having issues. The second one is a two-seconds-to-black issue. The first one, the one I'm starting with, fires up just fine for about ten minutes until the backlights shut off. I can turn the monitor off and back on again immediately and she'll come back up for five or ten mins, then out again. Repeat until sleepy.

I swapped boards with the 2-to-black monitor just to see what'd happen. Well, the problem didn't exactly follow the board, I was left with TWO 2-to-black monitors. Neither would give me more than a quick flash. The only combination that sorta worked was this one, ten mins to blind.

So, none of the caps looked bad visually so I figured what the heck, replace 'em anyway. It's "always" caps right? Well no such luck, I replaced all ten (all but the large one) and no change. While running I checked for anything overheating with my temp probe and nope, nothing overly hot... I did notice an odd squealing sound though that I couldn't pinpoint. Transformer? Backlights?

As luck would have it I have an old Acer in the other room with no power supply but good backlights. Plugging the Acer lights into this board I get full light for at least half an hour and no squealing. That narrows it down to the backlights. Okay...

Now correct me if I'm wrong, but I figured I could unplug one of the Acer's lights at a time and replace it with the original Philips light until the squealing came back, telling me which light is toast. Sound right? Well, it'll only squeal when both of the bottom connectors are plugged in with the Philips lamps. With the Acer's plugged in to the bottom and with either in at the top, no squealing. With one of the Acer's plugged in at either connector at the bottom and anything in the rest, no squealing. With two Philips in the bottom connectors, squealing and ten minutes of life.

So where does this leave me. Am I on the right track in thinking that it has two flakey backlights and will work fine with one but not both? I really can't explain why it won't power up for more than a second with the other Philips screen though... I think the second Philips has an open circuit across one of the transformers, I really can't explain how that one is powering up at all. One problem at a time, it'll be next.

*sigh* So much for a simple cap job...

[retiredcaps]

Re: Philips 190S ten mins to black

You guys like detail, right?

Absolutely. When it is well written with paragraphs, punctuation, proper nouns, clear photos, and capitalization, it makes remote troubleshooting a lot easier. Too often, we get lazy posters who think this is twitter or don't bother with proper sentences.

It sounds like you are on the right track. Have a read through posts #19 and #20 to see if there is a tip that helps you out.

https://www.badcaps.net/forum/showthread.php?t=10419

Pay attention to the section regarding bad ccfls and/or wiring. Sample photos of both are in the guide so you know what to look for.

PS. Even though it takes 10 minutes for the lcd to go to black, it is still a "2 seconds" type of problem. The ccfls are on the verge of dying or the wiring internally is fraying and not making good contact. Turn the brightness/contrast up or down accelerates or delays the problem.

[Jasgriff]

Re: Philips 190S ten mins to black

Hi and welcome to the forum,

Brilliant explanation and good pictures. This always makes it easier to help you get to the bottom of your issue. It also tends to make members more keen to help you out.

It seems that you have done lots of leg work already which is good. I see that retired caps has pointed you to the bible of testing which help you either eliminate of discovery where the fault coming from.

I see you talking about 2 Philips monitors? If so then you can test the inverter's on both to see I they measure correctly. Retired caps guide shows you how to do this.

[SBlackfoot]

Re: Philips 190S ten mins to black

Thanks for the help, gentlemen. I really appreciate it.

With work and family and all I haven't had a heck of a lot of time to do any major troubleshooting since my last post. I did do a little more quick component swapping between the two monitors though (The two identical Philips, aside from an RF shield over the logic board in one).

Here goes. The inverter I recapped from monitor #1, along with Monitor #1's logic board, work just fine with the panel from #2. The backlights all light up and stay lit for a good half hour until the monitor goes into standby. This is the only combination that seems to work.

If I use the recapped #1 inverter board (good) on the #2 panel (also good) with #2's original logic board, less than two seconds to black. This implies some damage to #2's logic board, and I already know that it's original inverter has an open circuit on one of it's transformers so I haven't played with it again. I have read online that this board needs a load from all four good lamps or else it'll shut down. Seems odd to me but it fits the symptoms, who am I to argue... *shrug*

So in summary, at face value, I'd say I have a bad backlight (or two) in #1's panel, and #2 has a bad transformer and something wrong on it's logic board. The caps look fine but I could replace 'em anyway. I'll post pics of the logic board when I get a chance during the day.

I also need to decide if it's worth the trouble of replacing two lamps, a transformer, and diagnose the logic board to get two working monitors when I have enough parts for one already... Too many monitors, too little time. lol

[SBlackfoot]

Re: Philips 190S ten mins to black

Oh one more thing that may be important. The squealing sound I noticed with monitor #1 and it's flakey backlights, it's almost definitely coming from the large transformer (Primary? Still working on the terminology). It only makes the noise when plugged into those original backlights, not the known good ones. I'm not sure how it's possible for that transformer to be making noise but hey, I am a rookie.