Hog1000 LCD backlights dark

guessiguessi Registered User
I'm with a used Hog1000 for half a year now and just noticed on another desk that the backlights for the LCD screens can be really bright. On mine they are so dark, you might not realize they are on.

Symptoms are: brightness control from Setup/Panel does work (3 steps and off), contrast control does work. Brightness (better darkness) is the same for all 6 LCD displays. No problem at all with main graphic screen, it is bright like the sun :-)

So I just opened the desk and had a closer look. The supply for the inverter is 12V, the control voltage for the inverter is 5V for step 3 (brightest) and reduced to appr 1,5V for off. Output is 230V AC for step 3 (brightest). One backlight (PB card 1) draws appr 6,5mA.

Are these values correct? Trying to say if the inverter is bad or the EL backlights...

fitted pcbs are BACKLITE4, ECHMENU2, ELTPBK2
serial nr 25CG300214

I do not understand the supply chain for the EL elements. Looks like menu card 1 to menu card 0 to PB card 0 to PB card 1. I assume the backlights are just connected in parallel?
If I unplug the last 2 wire supply connector on PB card 1 not only the backlight of that LCD menu is off but also all the other LCD backlights will get even darker! If I unplug the connector between menu card 0 and PB card 0 the menu cards backlights are totally off.
Whereas directly connecting the cable to PB card 0 to the inverter will let the PB cards backlights work, although not much brighter and with reversed behaviour (step 1 is brightest, step 3 darkest!).

Is there anybody having ideas about the topic?
Thanks a lot!


  • MitchMitch Registered User, HES Alumni
    edited January 2012
    Over time the backlights do wear out and get dim and that seems to be what you are seeing. The voltages look ok so I think the backlights themselves are the most likely cause of the problem.
  • guessiguessi Registered User
    edited January 2012
    Thanks for the info!
    It looks like one might "just" unsolder the 2 contacts of the EL foil and pull it out from underneath the LCD?

    I still don't understand why voltage and frequency change when you change the number of backlights connected...?
  • MitchMitch Registered User, HES Alumni
    edited January 2012
    Hello, it is a non-regulated supply so the values will change depending on the load.
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