DragonOSD+ black border contrast mod
Posted: Sat 03 Apr 03 2010 2:15 am
Note that these contrast mods are work in progress and some parts may not be complete. Before you perform the mods, talk to me. In the meantime, I am working on an add-on solution which may prove to be easier to use for most users.
In particular, some of these mods could cause sync to be lost when the menu selection bar appears on certain portions of the screen due to the lack of voltage clamping. Again, I hope to have this addressed soon.
(Note: The diode reversal modification is being deprecated. Simply REMOVE THE DIODE altogether. Much easier to do.)
I have noticed that with some equipment, the text border doesn't appear as black as I would like it to be. This thread deals with various mods that I am trying out in order to improve this situation. The first modification that should be done is to reverse diode D1 as indicated in the image below:- The changes may not be very noticeable but with some types of equipment, this could show some improvement. Since the board uses high temperature solder, you should use an iron set to around 350 degrees C for this job. Heat up one leg while lifting that end of the diode gently. It doesn't matter if it doesn't come off completely on the first go, just so long as it comes off a bit. Then turn the board around and do the same for the other leg. Heat it up while lifting it gently with a pair of tweezers. Repeat with leg 1 and 2 alternatively until the diode comes off. Then turn it around and solder it back one side at a time. The side of the diode without the "bar" should be towards the edge of the board and should be the opposite orientation of the adjacent diode (also marked A2).
After doing this modification, your video may look a little brighter.
Voltage-level modification - 1k resistor
The second part of the modification involves a small 1/8-watt 1kohm 5% resistor (brown-black-red-gold). This needs to be soldered from the video input to the 3.3V supply. The suggested method of doing this is as follows:- If you find the blacks too black, you can use a 1.5kohm resistor instead of the 1kohm resistor.
The following photos show the effects of the modification:-
Base pull-down resistor modification - stacked 10k 0603 resistor
Now, after performing the above modification, you may find that the black border is too thick and you want to pull it back just a tad to keep things nice and clean. In order to do this, you will need to make another minor modification - soldering an additional 10k 0603 SMD resistor over one of the onboard resistor. This means that the new resistor will be stacked over the existing one as follows:- The impact of this change is as follows:- Daniel
In particular, some of these mods could cause sync to be lost when the menu selection bar appears on certain portions of the screen due to the lack of voltage clamping. Again, I hope to have this addressed soon.
(Note: The diode reversal modification is being deprecated. Simply REMOVE THE DIODE altogether. Much easier to do.)
I have noticed that with some equipment, the text border doesn't appear as black as I would like it to be. This thread deals with various mods that I am trying out in order to improve this situation. The first modification that should be done is to reverse diode D1 as indicated in the image below:- The changes may not be very noticeable but with some types of equipment, this could show some improvement. Since the board uses high temperature solder, you should use an iron set to around 350 degrees C for this job. Heat up one leg while lifting that end of the diode gently. It doesn't matter if it doesn't come off completely on the first go, just so long as it comes off a bit. Then turn the board around and do the same for the other leg. Heat it up while lifting it gently with a pair of tweezers. Repeat with leg 1 and 2 alternatively until the diode comes off. Then turn it around and solder it back one side at a time. The side of the diode without the "bar" should be towards the edge of the board and should be the opposite orientation of the adjacent diode (also marked A2).
After doing this modification, your video may look a little brighter.
Voltage-level modification - 1k resistor
The second part of the modification involves a small 1/8-watt 1kohm 5% resistor (brown-black-red-gold). This needs to be soldered from the video input to the 3.3V supply. The suggested method of doing this is as follows:- If you find the blacks too black, you can use a 1.5kohm resistor instead of the 1kohm resistor.
The following photos show the effects of the modification:-
Base pull-down resistor modification - stacked 10k 0603 resistor
Now, after performing the above modification, you may find that the black border is too thick and you want to pull it back just a tad to keep things nice and clean. In order to do this, you will need to make another minor modification - soldering an additional 10k 0603 SMD resistor over one of the onboard resistor. This means that the new resistor will be stacked over the existing one as follows:- The impact of this change is as follows:- Daniel