Film-Tech Forum ARCHIVE: Planar PT1545 Monitors

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Posted by Mark Gulbrandsen (Member # 72) on 07-26-2017, 02:33 PM:

Just an update on the direction I went with these. Repairing the CCFL circuit can be done, but is basically a waste of time as the semiconductors are only available out of China and a bit pricy. So I have been converting them to LED back light. Taking the LCD panel apart on these is fairly easy to do and I have done about a dozen of these now, and have my repair time down to about an hour not counting time for the silicone to cure that I use to glue the LED strips into the metal reflectors. Locating the back light switching voltage was also a bit tricky. The LED lighting needs to shut off with loss of video just like the CCFL does. If anything the LED back light is a tad bit brighter and has better contrast then the CCFL does.

Posted by Dave Macaulay (Member # 813) on 07-26-2017, 09:29 PM:

Although elegant, why "must" the LEDs shut off on video loss?

Posted by Buck Wilson (Member # 5885) on 07-26-2017, 09:38 PM:

Excellent! Start a return/service program!

Posted by John Roddy (Member # 7348) on 07-26-2017, 10:41 PM:

What's the power draw of the display with LEDs compared to CCFL? I'm wondering if it's possible to just junk the power board and replace it with a 12V/5V external brick. That would open up some interesting possibilities for power delivery…

Posted by Marcel Birgelen (Member # 6801) on 07-27-2017, 08:20 AM:

quote: Dave Macaulay
Although elegant, why "must" the LEDs shut off on video loss?

To save power and hours on the LEDs I presume.

It's pretty normal for a monitor to go into standby mode after the input signal is lost.

Posted by Mark Gulbrandsen (Member # 72) on 07-27-2017, 11:01 AM:

quote: Dave Macaulay
Although elegant, why "must" the LEDs shut off on video loss?

Because if one loses the video feed as in shutting down the server, the LED's stay on but the actual screen power still shuts off, and then the screen goes bright white. It would do the same thing if the CCFL lamps did not shut off.

quote: John Roddy
What's the power draw of the display with LEDs compared to CCFL?

LED = .9 amp. CCFL = 1.15 amps. So the LED's draw just a tad bit less power. I could also include a potentiometer to be able to adjust the LED brightness. But it is just about right the way it is.

Mark