Samsung UN55HU6840 No picture has sound and backlights

[2smoovedaddy]

I got this Samsung pretty cheap and thought it would be an easy fix but I'm getting sound and back lights but no picture. Already tried to to re-seat the cables on the t-con board and detached them one at a time with no success. Also replaced the t-con board(ebay) with no success. Also when I power it up I see the red light flash five times don't know if that's normal. I've attached pics. Any where I can get a manual without having to pay. Went to Samsung website and they're charging for the service manual. Any help would be appreciated. Thanks!

[dskall]

Re: Samsung UN55HU6840 No picture has sound and backlights

Make sure you are getting t-con voltages

T-con voltages (typical)
1. Vin (Vcc): 12Vdc or 5Vdc
2. Vdd (Vlogic, Vddd): 3.3Vdc
3. Vda (Vs, Vsource, Vdda,Avdd): 14Vdc~20Vdc
4. Vgh (Vgon, Von, Vddg): 20Vdc~30Vdc
5. Vgl (Vgoff, Voff, Veeg): -5Vdc~-7Vdc

[2smoovedaddy]

Re: Samsung UN55HU6840 No picture has sound and backlights

Thanks for the response dskall. I'm getting no voltage in any of those areas of the t-con board.

[dskall]

Re: Samsung UN55HU6840 No picture has sound and backlights

What do you get at fuse with 2616 on top. Voltage Either side?

[2smoovedaddy]

Re: Samsung UN55HU6840 No picture has sound and backlights

No voltage on either side.

[dskall]

Re: Samsung UN55HU6840 No picture has sound and backlights

Need to make sure you are getting all your voltages to main board. Missing your 12v. Ether not getting it from power supply, bad regulator on main board or transistor or command to transistor is missing. Your 12v looks like it comes in on left side of ldvs cable through multiple traces so unlikely bad cable.

[dick_barton]

Re: Samsung UN55HU6840 No picture has sound and backlights

Can you list your power supply voltages giving legend name and voltage read.

[2smoovedaddy]

Re: Samsung UN55HU6840 No picture has sound and backlights

1. P_DIM1=3.27v
2. N. C =0v
3. Gnd=0v
4. Gnd=0v
5. UD =2.32v
6. Blu_on =3.13v
7. Gnd=0v
8. Vamp=12.79v
9. Vamp=12.79v
10. Vamp=12.80v
11. B13v=12.79
12. B13v=12.79
13. B13v=12.79
14. B13v=12.79
15. B13v=12.79
16. B13v=12.79
17. Gnd=0v
18. Gnd=0v
19. Gnd=0v
20. Gnd=0v
21. A5v=5.31v
22. A5v=5.31v
23. Gnd=0v
24. PS_On=3.34v

[Andrew F. Ali]

Re: Samsung UN55HU6840 No picture has sound and backlights

The 12Vdc for the T-CON comes from the Main Bd. There is a transistor switch not being turned ON. Trace the line by continuity test from the T-CON fuse on the to the Main Bd. Then trace the Main Bd LVDS jack to find the transistor switch. That is how I did it twice already on other TVs I didn't have the schematic for.

[2smoovedaddy]

Re: Samsung UN55HU6840 No picture has sound and backlights

Are you talking about this area. I'm getting continuity on the pin shown in the pic. If so where do I go from there. Thanks!

[dick_barton]

Re: Samsung UN55HU6840 No picture has sound and backlights

It does appear as though the 12V Tcon missing supply is a main board problem and as Andrew said above, it's a matter of tracing the 12V supply from the Tcon and following its path on the main board.

[dskall]

Re: Samsung UN55HU6840 No picture has sound and backlights

If you are only interested in fixing tv I would get another main board. If like me and it is hobby and learning experience then follow Andrew F. Ali advice above. Tracking mainboard problems can be daunting especially without schematics.

[dick_barton]

Re: Samsung UN55HU6840 No picture has sound and backlights

How about a close up photo of that area but with the black heatsink lifted so that the components can be more easily identified.

[Andrew F. Ali]

Re: Samsung UN55HU6840 No picture has sound and backlights

How about a close up photo of that area but with the black heatsink lifted so that the components can be more easily identified.

With the heatsink removed, trace that pin to its source. It may end at the transistor's collector or source depending if it's a bi-polar or FET type transistor. In my cases the transistor was open cct as the base or gate was getting signal/voltage.

[2smoovedaddy]

Re: Samsung UN55HU6840 No picture has sound and backlights

Here's a close-up. I'm getting resistance on the c,b,e on the transistor in the pic.

[dick_barton]

Re: Samsung UN55HU6840 No picture has sound and backlights

What voltages do you have on those pins and when you bring it out of standby?

[2smoovedaddy]

Re: Samsung UN55HU6840 No picture has sound and backlights

I'm getting 3.32v on the base, 3.29v on the top right( can't tell if it's base or emitter) and 0v on the top left. I'm getting continuity on the 4 bottom pins on the chip in the pic from the fuse on the t-con board. Also that chip looks like it has been replaced before. Might be refurb. Could the chip be bad and not regulating the voltage as the transistor seems to be fine per continuity check.

[2smoovedaddy]

Re: Samsung UN55HU6840 No picture has sound and backlights

Meant to post this pic of the chip.

[dskall]

Re: Samsung UN55HU6840 No picture has sound and backlights

For the ic you circled the first three from upper right side are source. Number four pin is gate and bottom pins are drain.

[dick_barton]

Re: Samsung UN55HU6840 No picture has sound and backlights

What's the part number of the IC?

Can you give the voltages Pin1 to Pin 8