A friend lent me a Wonderboy PCB to repair, and whilst playing with it I noticed it was displaying a very blurry picture from my H.A.S.
Tracking the RGB lines back from the edge I found they go thru a 1k resistor array for termination.
The blurry picture looked like when an RGB mod has poor termination.
I socketed the array area and tried out some different value arrays.
The closer to 75r the better, I couldn't find any so just used a 100r array, the picture is emulator sharp now.
original 1k array on the left, 100r array on the right.
Sega System 1 - Blurry picture fix?
Sega System 1 - Blurry picture fix?
Last edited by Syntax on Wed Mar 20, 2024 2:59 pm, edited 1 time in total.
Re: Sega System 1 - Blurry picture fix?
Is there a way to test the original array to see how much the value has changed from original? Or did something else potentially change that makes the video output better with a different than original spec resistor bank?
-
Konsolkongen
- Posts: 2318
- Joined: Fri May 16, 2008 8:28 pm
- Location: Denmark
Re: Sega System 1 - Blurry picture fix?
The colors look very different after the mod. Is that what they should look like?
Re: Sega System 1 - Blurry picture fix?
Ill get a proper capture, using a Samsung phone camera was not a good idea for comparison.
Edit*********** Added capture to first post.
It does show the colors are off... :/
Edit*********** Added capture to first post.
It does show the colors are off... :/
Last edited by Syntax on Wed Mar 20, 2024 3:07 pm, edited 2 times in total.
Re: Sega System 1 - Blurry picture fix?
The array loads each colors 3 bits by a percentage by using some resistors in parallel for some of the bits. It uses one of the resistors for termination.
Changing the array keeps the divisions the same but lowers the termination.
I unfortunately have no color bar screen output for this PCB so cannot tell if 100r is too hot and crushing some colors.