pzlate
New member
UMK3 board playing blind 7407 inputs shorted to ground
Need a bit of guidance here. I have a board where everything works fine, but it's playing blind, it's definitely passing the hardware test and it has sound. It's outputting the correct resolution and refresh rate but just a blank image.
I've already swapped U45 and U47. I saw a post saying that replacing 7407 fixed a loss of color, but that didn't fix it. However I did notice that all the inputs on the 7407 at U91 right now are pegged low and shorted to ground. I traced the input back to the hex inverter on U75 and that input (pin 13) is also shorted to ground.
Replacing both did not change anything, and I can't seem to find the source of the short to ground. This board is 99% there, just can't figure this out and it's bugging me, it's very clean board otherwise.
e: A bit of extra info if I short the ALS541(U82 and U97) VCC and OE2 pin next it with my probe it will also have continuity with ground.
Need a bit of guidance here. I have a board where everything works fine, but it's playing blind, it's definitely passing the hardware test and it has sound. It's outputting the correct resolution and refresh rate but just a blank image.
I've already swapped U45 and U47. I saw a post saying that replacing 7407 fixed a loss of color, but that didn't fix it. However I did notice that all the inputs on the 7407 at U91 right now are pegged low and shorted to ground. I traced the input back to the hex inverter on U75 and that input (pin 13) is also shorted to ground.
Replacing both did not change anything, and I can't seem to find the source of the short to ground. This board is 99% there, just can't figure this out and it's bugging me, it's very clean board otherwise.
e: A bit of extra info if I short the ALS541(U82 and U97) VCC and OE2 pin next it with my probe it will also have continuity with ground.
Last edited: