Technika TX22D14BTCDG963  TV

Fixing the QRN!

Almost a year ago, I went out and bought a Technika Television of the LCD variety from a large grocery chain whose name starts with T and ends on O.  It was a model TX22D14BTCDG963. It was relatively inexpensive for a 22 inch LCD display TV at a bit over £200, and incorporates a DVD player that plays almost anything I can throw at it.  I actually bought it for use in the shack, in large part because it has a SAMSUNG LCD display, for use as a PC monitor and not a television. In fact I have NEVER used it for it's intended purpose... a TV, although I have watched DVD's on it and listened to MP3s.! As a display device, I'm delighted with it, but it does have a dark side.  It's used with my home-build PC, a simple low tech ATOM based board with a terabyte of disk storage.  There's only one fly in the ointment... QRN from the 'TV'.

It generates broadband RF hash over the HF spectrum and into VHF. It makes use, like most TV's and displays, of a Switchmode PSU and has only a two core mains cable.  What attracted me to this 'TV' was...

1) It employed a Samsung LCD panel (good quality)

2) It had all the interfaces I wanted including VGA and HDMI.

3) It was compact and suited my shack.

4) The price was attractive.

I noticed after installing it that noise levels on HF and VHF had increased considerably but lived with the problem.... until today. I thought it could be improved, so I opened it up for a look. The LCD panel is clad in aluminium on all sides except for the front... of course!, and there is a PSU board plus the actual TV electronics on a separate PCB.  I checked for continuity between all the metal parts of the TV and the pins of the mains plug.

It was open circuit in all cases, so I set about changing the mains lead to a three core type and added grounding wires to both the LCD's metal  back panel and the negative side of the switchmode PSU. While I was at it, I added a couple of ferrite tubes to the new three pin mains lead within the chassis.  I was a bit unhappy that the electronics was NOT housed in a proper faraday screen but my alterations paid off. The TV is now VERY much quieter from an RFI point of view.  HF reception is back to normal in my shack.

So, to recap, the only things I did to create this state of amateur radio bliss were...

1) Change the twin core mains lead for a three core type.

2) Provide a ground for the negative side of the PSU output and the metal screen of the LCD.

3) Add two ferrite tubes over the mains lead inside the TV cabinet.

My point in making these mods was to demonstrate what a p**s poor job some manufacturers do of building decent consumer equipment.... and to ensure an RF quiet life. It was a big success.

The alterations were very inexpensive and very easy to do,  so it begs the simple question... Why can't Technika do a proper job of building their LCD TV's?   To be fair to Technika, they are not alone in being cheapskates when it comes to bodging up basic design, to save what amounts to pennies. There are even more companies out there (Chinese mainly) cutting corners to bring products to the marketplace that minimise build cost while maximising profits, at the expense of poor RFI performance.  Nowhere is this more obvious than in the design of Personal Computers imported from China. The manufacturers will design a decent switch-mode power supply to get that all-important CE certification, but when it comes to production lots, the components forming the all-important mains filter is nowhere to be seen... replaced by empty spaces where the capacitors should be, and wire links where the inductors ought to reside.  So, ask yourself... what is CE certification really worth?

Shocking and inexcusible IMHO! 

GM1SXX