Hisense 58A6KV

[Diah]

I already tried the 12v injection from main board to tcon board and rgb test begins but screen goes dark as soon as the HVAA voltage drops from 7.99v down to 3.34 v .I only see about 2 colors mostly yellow on entire screen but it quickly fades away .The backlights also come on and stay on.

then you are close to find the issue... do it again and disconnect half screen..... with one U ribbon disconnected on the same side.... when the issue always here... T-CON Spi need to check it.. or flash firmware... panel driver cause such issue too... 6 years or more i g´faced one on Hisense and just small size bin file solve it i go it from China... i have threat on it over here

[Davi.p]

was a faint suspicion, that on the tcon 1 where you see the VAA & HVAA testpoints, in between there is a broader trace with 1,8v supply voltage, what i thought is that there is a physical shorted conection between HVAA and 1,8v, even a bad connector of fpc ribbon, maybe for some reason the HVAA it is activated backward at a certain moment..

[Helikvar]

was a faint suspicion, that on the tcon 1 where you see the VAA & HVAA testpoints, in between there is a broader trace with 1,8v supply voltage, what i thought is that there is a physical shorted conection between HVAA and 1,8v, even a bad connector of fpc ribbon, maybe for some reason the HVAA it is activated backward at a certain moment..

I tried the step below recently to see what would happen to IC5.(If it still got scorching hot)
. I noticed that L5,D18 and C31,C33,C34 formed a dc to dc buck convertor and thought that possible IC5 was providing the switching mosfet for the circuit.
. All the other coils have mosfets for switching power supplies with the gates controlled possibly from IC5.L5 doesnt have a descrete mosfet so I went with the presumption IC5 was doing the switching and wanted to see if IC5 would stop getting hot if I removed L5.
. With L5 removed IC5 stayed cool to the touch so that seems to indicate that that buck circuit may be responsible for the chip getting extremely hot.
. Also with that coil removed vgh and vgl voltages disapeared as well as HVAA.
. Coil has been put back and ic5 is back to getting very very hot again and I don't know if what I did is helpful or not .
. The HVAA voltage seems to be produced on the right control board connected to the lcd panel .It then passes down thru the ribbon cable to the tcon board across top of tcon board back up other ribbon cable and feeds the left panel with HVAA voltages.

[Helikvar]

then you are close to find the issue... do it again and disconnect half screen..... with one U ribbon disconnected on the same side.... when the issue always here... T-CON Spi need to check it.. or flash firmware... panel driver cause such issue too... 6 years or more i g´faced one on Hisense and just small size bin file solve it i go it from China... i have threat on it over here

I did the ribbon method as well as the tape method also but only got one half screen black ,one half white and removing other ribbon all black screen .
. After studying the right control panel board attached to screen or tcon 2 as Dave put it I see that pulling either ribbon cable will disconnect HVAA from both panels and with the HVAA voltage going down to 3.4v the screen will never show a pic.

[Davi.p]

OK so the most suspected are the 3 caps or D18 that have anode to gnd , remove them or better replace them

[Helikvar]

OK so the most suspected are the 3 caps or D18 that have anode to gnd , remove them or better replace them

Have replaced all 3 caps and D18.Same symptoms as before .All voltages come on and hold steady except for HVAA which starts at 7.99v and seconds later drops to 3.45v
. IC5 still very hot over 102° C last time I read the temperature.

[Davi.p]

Yes, after writing my last post i thought there was not much probabilty it worked, now what is needed is to know if the HVAA is the problem or its load, so remove R21 and u can see the heat of IC and HVAA, if same symptom, then you can, with R21 away, get the VAA and form a divider, so VAA ----||----HVAA-OUT---||----- GND....

NOTE: i would use 20uF caps..

[Helikvar]

With R21 removed and reading HVAA from C221 the voltage holds steady at 7.92v and IC5 no longer heats up.So obviously the load is the problem and not the chip.Does this mean it most likely is the panel and that's the problem .

[Davi.p]

you can try to trace if there is another component on the path past the resistor.. i never know what the hvaa is for, it is surely for source e drivers, maybe after seconds it shorts with vcc33, now i'm short on ideas, see you later im going to work..