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820-00923 No Internal Video

brunomotter

brunomotter

Member
Hello. Got this board here a couple of months ago that was not powering on. I fixed it and now it turns on and works with external display but no internal. I ordered a new LCD assembly to test, which works on another machine, but on this machine it does not work, just like original one. No video and no backlight. Tried replacing LVDS cable, still same. Where can I begin the troubleshooting? I tried replacing U8500 as it was getting 5V and I thought it may be not sending out PP5V_S0SW_LCD but still same.
 
2informaticos

2informaticos

Administrator
Staff member
Did you change it without checking if output voltage is present?

Check J8500 basic voltages; pins 44, 45, 6.
If good, check diode mode to ground at EDP_INT data lines.
 
2informaticos

2informaticos

Administrator
Staff member
Check mentioned voltages at the same time when the machine chimes.
You should get a pulse for 2-3s at least.
Also check EDP_PANEL_PWR_EN at same time.
 
brunomotter

brunomotter

Member
EDP_INT_AUX_N - 0.002
EDP_INT_AUX_P - 0.238
EDP_INT_ML_N<0> - 0.281
EDP_INT_ML_P<0> - 0.279
EDP_INT_ML_N<1> - 0.275
EDP_INT_ML_P<1> - 0.276
EDP_INT_ML_N<2> - 0.276
EDP_INT_ML_P<2> - 0.276
EDP_INT_ML_N<3> - 0.276
EDP_INT_ML_P<3> - 0.276
 
2informaticos

2informaticos

Administrator
Staff member
"EDP_INT_AUX_N - 0.002"
As expected; CPU's eDP output is damaged.
There are no series capacitors to protect data lines.
 
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