[CQ-Contest] Sony TFT LCD Monitor SDM M81 blackened by RFI

[Earl Morse]

Barry,

The darkening of your panel sounds like your backlight power supply/inverter is getting RF into it and is being shutdown.  These power supplies are analog and therefore more susceptible to interference than the digital data.  Removal of the RF causes the power supply to recover and backlights to come back on.  These backlights are flourescent and the power supplies generate about 400-500 Volts at about 50-100 kHz.

The beads on  the video cable may not have much effect.  You may need to go inside and shield the backlight power supply or put beads on the dc lines that this inverter operates from.

BTW, you can check if it is the backlight by holding a light close to the panelwhile witnessing the phenomena.  If it is just the backlight you will still be able to see the display if you can illuminate the panel.

Good luck
Earl
N5TU



CQ Contest Digest wrote:

> ------------------------------
>
> Date: Sun, 27 Jan 2002 14:01:33 -0600
> From: "Barry Merrill" <barry at mxg.com>
> Subject: [CQ-Contest] Sony TFT LCD Monitor SDM M81 blackened by RFI
>
> In the CQ 160 Test this weekend, I discovered
> that RFI could blacken the screen of my new
> "SONY TFT LCD Color Computer Display SDM M81".
>
> There were no problem on all other bands, but on 160,
> where I disconnect the shield of the 80 dipole's coax
> at the antenna switch in the (second floor) shack,
> even with SWR from only 1.2 at 1800 to 2.7 at 1855,
> whenever I used 800 watts and a 22-wpm dash (or 1100
> watts and a dot) of the Alpha, the Sony Monitor blacked
> out instantaneously, and then remained black for three
> more seconds after key up, before snapping back to life.
>
> The monitor was directly adjacent and close to the Alpha,
> but moving it 3 feet away did not change the problem,
> so I presume the RFI is getting in thru the cable,
> which I'll try to relocate and/or rf-choke thru a toroid.
>
> Fortunately, I discovered that 3 seconds is exactly how
> long it takes you to type in my call, see that I'm not a
> dupe, hit F2, and for your keyer to get to the State
> part of your exchange, so I was able to see to type just
> when I need to!
>
> Barry, W5GN
>
> Herbert W. Barry Merrill, PhD
> President-Programmer
> MXG Software
> Merrill Consultants
> Dallas, Texas, USA
> 214 351 1966
> www.mxg.com
>


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