A2338 - 820-02020-A no image

[hgoncalves]

Hi,

I have an A2338 - 820-02020-A with no image.

Already tried with new display, but same result; no image.

However, I have image on external monitor.

Not sure where to start, but:

PP3V3_S2 = 0V and 0.003 on diode reading, and 0.01ohm resistance to ground

P3V3S2_PGOOD = 0V and 0.682 on diode reading

PPBUS_AON_3V3S2_VIN_ISNS = 0V and 0.002 on diode reading

PP3V3_AON = 3.287V

PP3V3_SW_LCD = 0V

Can the culprit be UC710?

Can you help?

 

[hgoncalves]

After replacing UC710, now PP3V3_SW_LCD, and PP3V3_S2 has 2.350V and still no image...

PPBUS_AON_3V3S2_VIN_ISNS = 2.782V

P3V3S2_EN = 1.310V

PP3V3_S2 = 2.350V

PP1V8_S2 = 1.8V
PP5V_S2 = 5.194V

P3V3S2_PGOOD = 0V

Any help?

 

[2informaticos]

3V3_S2 is still low; that's why its power good signal is not present.

Check RC709-13 and their traces.

 

[hgoncalves]

HI,
Tks for the help.

All RC709-13 are ok (normal resistance values), and their traces are also ok.

Just notice that P3V3S2_PGOOD starts with 3.261V and then drops to 0V and 3V3_S2 starts with 3.290V and then drops to 2.350V (after about 15 seconds)

 

[2informaticos]

What is the behavior of P3V3S2_EN?

 

[hgoncalves]

P3V3S2_EN start and stay stable at 1.317V

 

[2informaticos]

It should be good enough, if 3V3_S2 starts with good voltage.
Enable signal probably comes from 1V8 logic side.
You can compare its level with another power enable coming from same side of U8100 (page 33).

UC710 overheats?
You may try to change it again, just in case.

 

[hgoncalves]

Hi,

While resoldering UC710 again, I notice that a bit of the PPBUS_AON_3V3S2_VIN_ISNS board pad was burnt (missing a piece). Howver it has continuity with CC721. Do you think it can be related?

UC710 doesn´t get hot. I don't have any more UC710 and can't find it online; Do you think i can order TPS621351RGXT instead?

 

[2informaticos]

Be sure to get correct voltage at pin 1/UC710.
Run wire over the trace, if needed.

Check if TPS621351RGXT has the same layout.
If yes, you can give it a try.

 

[hgoncalves]

Hi,

Pin 1/UC710 (PPBUS_AON_3V3S2_VIN_ISNS starts at 10V and then drops to 2.782V

PPBUS_AON is 11.98 steady. Can it be RD560 the culprit?

I presume that was because of 3V3_S2 problem. Shall i address this first?

 

[2informaticos]

Then you have a problem with RD560, or its traces.

 

[hgoncalves]

HI.

It was that.
TKS!!