Icom IC-756 Pro II CCFL to LED Part 2 of 3 connecting to the internal LCD brightness adjustment.

[@denisthacker9825]

Do you still do these modifications ?

[@antoninorusso56]

I saw that you have completely removed the driver board of the two LED bars and in its place you put the circuit with a transistor ... This means that to drive the two LED bars there is no need for the driver circuit .. They are powered directly from the 14 V supplied by the apparatus ... and the sampling point of the dimmer line is that taken from inside the inverter of the CFL (which ranges from 0 to 4.6 Volt approximately) Now, if you look closely the 2nd part video, the setting is ... but it's not that great ... So, in my humble opinion, it is advisable to leave the driver card (with the pick-up point of the dimmer line on the transistor Q905 collector where this meets with the R915 - Front unit card. This offers two improvements, compared to the simple transistor and direct supply of the led bars: - 1) - When the RTX goes into transmission, the brightness of the display does not undergo lowering (as it could have without its driver, or without inserting a further integrated upstream regulator, eg LM7812; 2) - the sampling point on the collector of the Q905, in addition to avoid piercing the metal screen of the inverter, offers a variation of voltage from 5.1 V to about 12 V (see diagram) which allows a wider range of control on brightness, in fact, by placing a 10 Kohm linear trimmer at the input of the dimmer line of the LED driver board, you get a truly "optimal" adjustment of the brightness range governed by the device menu .. !! (in practice allows me to set as I like what will be the maximum brightness of the display when the Brightness menu shows me 100% and therefore also adjust the minimum (50% or 0%). Congratulations for the excellent work and I greet you cordially.

[@bandcam]

Hi Antonino, thanks for the words of wisdom, i assume from your comments you have done a modification on your own equipment? after reading and looking at the connection for the dimmer you talk of it seems you are dimming the panel meter and lights along with the screen back-light, this i had not considered but from what you say i plan on doing a few tests to see what can be done using your methods , I found that loading the original back-light connection from the Invert-er side was loading the circuit and was unable to get required voltage swing, as the led driver board dims the led's to a low maximum dim with 4,8 v supplied and comes to max brightness lowering the voltage to 2,5 v so as you can see using the LED driver board does not work in the voltage swing range and possibly not from the connection you suggest, that's why I used a single transistor, also regarding piercing the metal screen of the inverter there is entry below from PCB side. awaiting your suggestions and thanks Barry G4LVD

[@antoninorusso56]

@@bandcam Hi Barry ... you're right, in fact the dimmer pick-up point indicated by me, may not work with the LED bar driver board working in the "reverse" direction as a dimmer voltage, so you should build an inverter with transistor, but it should work perfectly with the circuit you made with 2N5294 transistors or equivalent ... and instead of the 10K fixed resistance I would insert a 10K resistive trimmer, this would improve the brightness levels of the led bars by adjusting it in broader way from a very low threshold to the highest one. Finally, the sampling point indicated by me is more accessible as it is directly connected to the collector of Q905 (near the point where we take the supply voltage +14 V) on the front card. Obviously it is all to be experimented and find improvements in this regard. Thanks to you ... and a greeting from me.

[@bandcam]

Antonino Russo ok all noted, at the moment I have to say I am very pleased with the current configuration, and am able to adjust the display down below a comfortable level and above a comfortable level which I was unable to demonstrate on the video as the camera keep compensating and correcting, so 50% looks good. I see no change whatsoever in the voltage or screen display when going from Rx to Tx as you questioned so all good there.. will keep experimenting haha...

[@bandcam]

Hi Antonino, check this out, kzbin.info/www/bejne/naqug3atlNOdqs0

[@АлександрКудревский-ч4б]

комментарии на русском были бы лучше а так остается только гадать