Hisense H55A6500UK backlight, sound but no display

[notallbad]

Tv turns on, backlights on but no picture, sound is present. Responds to remote, mute, voll up/down etc..
On initial power up the red led comes on solid, then switch on red led blinks 17 times. After initial power on from stby to on theres just 4 red blinks. (just for info really).

PS: RSAG7.820.7748/ROH
Main : RSAG7.820.7970/ROH
T-con : RSAG7.820.7932/ROH
Panel : HD550S3U51-TA

PSU voltages:
XP701
Stby-----On
110------125.7
0----------0
110------125.7
0----------0

XP805
---------Stby---------On
gnd------0----------0
ana------0----------0
vamp---18.4-----18.6
vamp---18.4-----18.6
gnd------0----------0
stb-------0.05-----2.69
12v------9----------12
12v------9----------12

sw-------0.03------4.69
bri-------0.03------1.53
gnd-----0-----------0
gnd-----0-----------0
nc-------0-----------0
gnd-----0-----------0
12v-----9-----------12
gnd-----0------------0

So, apart from the ana pin I guess these all look good?

Theres no obvious damage on either side of any of the boards and appear to be getting various voltages that look good around the main board and getting 12v, 1.2v & 1.8v on the T-con.

Theres a very, very faint 4 inch wide vertical bar around the middle of the screen which lines up with one of the tabs so its possible even if the tv can be fixed there will be bigger issues ahead, tab bond fault!

[dick_barton]

Re: Hisense H55A6500UK backlight, sound but no display

Are you saying the 12V supply is currently 9.12V

[notallbad]

Re: Hisense H55A6500UK backlight, sound but no display

Sorry. the spacing has come out wrong in the post.
Edited post to separate them out.
The 12v lines are 9v in stby and 12v when powered on.

[Diah]

Re: Hisense H55A6500UK backlight, sound but no display

try to downgrade the firmware before you go on yours thought.

and check before all if you have VCC 12V on the T-CON

[dick_barton]

Re: Hisense H55A6500UK backlight, sound but no display

I notice the board says 12V @ 3A, 16V @1.5A and 160V @ 450mA
Do you have the 16V and 160V supplies?

Edit
Just noticed that it looks like the 16V is the 18V supply

[notallbad]

Re: Hisense H55A6500UK backlight, sound but no display

Theres 18v on VAmp on XP805 connector and 125v for the backlights on connector XP701.

[dick_barton]

Re: Hisense H55A6500UK backlight, sound but no display

The backlight voltage appears low as per what's written on the psu.
Can you clearly see the backlights are up nice and bright from the back of the panel?

I have seen that you say the backlights and sound working but no picture.

[notallbad]

Re: Hisense H55A6500UK backlight, sound but no display

Yh, the backlights are definately on and bright.

Disconnecting the T-con ribbons to the panel boards one at a time makes no difference, still no picture/menu.

[nomoresonys]

Re: Hisense H55A6500UK backlight, sound but no display

See if there's voltage on each side of tcon fuse, pos. probe on each side, neg. probe on chassis ground.

[notallbad]

Re: Hisense H55A6500UK backlight, sound but no display

Yh 12v on both sides of fuse and 1.8v on vcc1.8 and 1.2v on FRC_1.2V1.

Appears to be a short across VD8 - MR340, even with one side lifted the short exists between the pads, not the diode.
Short across caps C238, C239, C177 and C176.

[dick_barton]

Re: Hisense H55A6500UK backlight, sound but no display

Is the MR340 the correct number?
https://tinyurl.com/y788q8ep and it appears to be a mosfet
Where is it on the tcon? top or bottom?

[nomoresonys]

Re: Hisense H55A6500UK backlight, sound but no display

Are those shorts there with nothing connected to tcon?

[notallbad]

Re: Hisense H55A6500UK backlight, sound but no display

M8R340 or MBR340, top right. DMM on diode setting get a reading of 120 one way only.
On the pcb pads get a short.
Sorry, picture upside down.

T-con disconnected from main and panel.

[nomoresonys]

Re: Hisense H55A6500UK backlight, sound but no display

That looks like a match, not sure on the postage, it just gave the rates to the U.S. when I clicked it: https://www.ebay.co.uk/itm/LVDS-TCON...EAAOSwgZ5cXu1e

[notallbad]

Re: Hisense H55A6500UK backlight, sound but no display

Yh, I think buying a replacement T-con might be the best way to go!

[neilc6]

Re: Hisense H55A6500UK backlight, sound but no display

Power up the tv with the tcon to panel ribbons connected one side at a time to confirm you dont have a panel fault.

[notallbad]

Re: Hisense H55A6500UK backlight, sound but no display

yh done that, no difference!

[dick_barton]

Re: Hisense H55A6500UK backlight, sound but no display

Short across caps C238, C239, C177 and C176.

It is possible that one of these caps are responsible for the short circuit.

[nomoresonys]

Re: Hisense H55A6500UK backlight, sound but no display

it is possible that one of these caps are responsible for the short circuit.

+10

[notallbad]

Re: Hisense H55A6500UK backlight, sound but no display

So, it would seem C177 was shorted.
Removed C177 and the cap is shorted.
The short across the other caps and the M8R340 has gone.
Also on the reverse side, VD5 showed as a short, but also now gone.

But what to replace it with? Its tied to the 12v rail. 0.1uf???

Dare I try it without this cap attached?