Welcome aboard Dounix. It's great you came back to detecting. Looking forward to your experiences with the Apex and your finds.
All the Best & Have Fun
Sorry for the delay and I'm not helpful for what you're asking about the TDI or 24K but... I own 3 Detech coils (7" Ultimate, 9" Ultimate & Arrow) and all perform better than the stock coils (compared to the 4x6, 6x10, 10", 1400, 950 & Super 12).
Hello chiil.
First off, you do a great job on this.
One question is, can you adjust the backlight brightness and will this take affect to the "dark" lines? My guess is the light is somewhat triggered and if it is switched "on" it is shortening the data from the display. Just a guess.
What I would try is to drive backlight directly from the battery but the current limited by a resisitor.
May be Carl Moreland can chime in.
So if someone is interested in buying "Digging Deeper With The DFX" or "The MXT Edge", by Jeff Foster, may be this will help...
--> http://www.digdeepdfx.com/
Those are the sad moments which make me cry. We know it is the best for the beloved; but never is for them who love them. May the Lord give strength to you, Linda, and your family and take care about Jim. My deepest sympathy.😢