Panrix Microelectronix
Member
Hey everyone, first time posting and hoping you can help..
A2141 had a small amount of liquid damage originally. It was displaying 20V but not booting correctly. We found a small amount of liquid damage on the board near U9080 & U9000. Both were removed and replaced. No shorts on the board before & after.
We booted the board and had no display but found we had heat on the board at UA900. This GPU power chip was replaced with all voltages showing after.
We found that we have the system now booting but no display. We checked the voltages at the connector (with a screen connected) and have our 3.3V & 5V for display but no voltage for backlight. We’ve plugged the machine into an external monitor and we do have a screen.
At the backlight driver (U8400), we have 5v input, and the other voltage inputs. We’ve confirmed the fuse has correct values. But have found we are missing the EDP_BKLT_EN signal from the GMUX. We’ve check to ensure it is not the driver pulling down the line or the resistor.
Tracing back to the GPU, we find that we are getting no EG_BKLT_EN into the GMUX. RA129 shows 0 at the GPU. We’ve tested against a known good board and should have 3.3v here.
We’ve tried to make this EDP_BKLT_EN signal by adding a wire and injecting voltage into the backlight driver but we still get no display and no output voltages from the driver (Sorry apart from BKLT_ISET_KEYB, which shows 1.2v. But no feedback voltages.
We are beyond the point of a economical repair, as it’s taken us a long time of diagnosing to get to this stage (we’re still new to MacBooks). But don’t wish to give up on this one. Is there anything we may have missed that would help?
A2141 had a small amount of liquid damage originally. It was displaying 20V but not booting correctly. We found a small amount of liquid damage on the board near U9080 & U9000. Both were removed and replaced. No shorts on the board before & after.
We booted the board and had no display but found we had heat on the board at UA900. This GPU power chip was replaced with all voltages showing after.
We found that we have the system now booting but no display. We checked the voltages at the connector (with a screen connected) and have our 3.3V & 5V for display but no voltage for backlight. We’ve plugged the machine into an external monitor and we do have a screen.
At the backlight driver (U8400), we have 5v input, and the other voltage inputs. We’ve confirmed the fuse has correct values. But have found we are missing the EDP_BKLT_EN signal from the GMUX. We’ve check to ensure it is not the driver pulling down the line or the resistor.
Tracing back to the GPU, we find that we are getting no EG_BKLT_EN into the GMUX. RA129 shows 0 at the GPU. We’ve tested against a known good board and should have 3.3v here.
We’ve tried to make this EDP_BKLT_EN signal by adding a wire and injecting voltage into the backlight driver but we still get no display and no output voltages from the driver (Sorry apart from BKLT_ISET_KEYB, which shows 1.2v. But no feedback voltages.
We are beyond the point of a economical repair, as it’s taken us a long time of diagnosing to get to this stage (we’re still new to MacBooks). But don’t wish to give up on this one. Is there anything we may have missed that would help?
