Samsung UE55F7005STXX - 5 blinks, screen dark

[Repair_dane]

Help needed:


My Samsung UE55F7005STXX will not start up.
The relay is clicking, but the only thing that happens is the red standby light immediately starts blinking 5 times. After some seconds the tv tries booting up again with the same result.
Two blue LEDS are lighting up on the t-con while it tries to boot.
No backlights, no sound, no image

When disconecting the main board, the backlights start up just fine.

Standby voltages are all good

I suspect a faulty main board and want to replace it, but apparantly this doesn't exist. Not on ebay, amazon, alibaba or elsewhere.
This tells me that this is probably a very common fault on this particular tv

So. As I see it the only option is waiting for one to show up or try to fix the main board.

Has anyone encountered a similar problem who can give any advice?

I don't have much experience with main board fault finding, so any advice would be appreciated

[nomoresonys]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Remove the connector at both ends, one end is connected to the power supply board, the other end is connected to the main board, see if there is any overheated sign on the connectors as in burn marks or discoloration?

[nomoresonys]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

I suspect one or more of those little mlcc caps, maybe hit them with a hairdryer then see if tv starts up if only for a bit, I knows theres a lot of them, you can check them for low ohms, unplug tv from outlet, unhook cables from mainboard to powerboard and tcon, one probe on each side, meter set to ohms, see if any are reading under 50 or so ohms or are shorted, could be a bad voltage regulator I guess?? Some mainboard testing there: https://www.youtube.com/watch?v=ocqnqmBxiqY

[neilc6]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Two leds on the the tcon is suspicious. Try powering the tv with only one side connected at a time with the ribbons from the panel to the tcon.

https://www.badcaps.net/forum/showthread.php?t=80010

There was another thread on a similar model where it was fixed after finding shorted caps on the bad side.

[nomoresonys]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Mainboard there, it's a pretty sick price tho: https://spares2repair.co.uk/samsung-...7v-bn94-06809g

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Remove the connector at both ends, one end is connected to the power supply board, the other end is connected to the main board, see if there is any overheated sign on the connectors as in burn marks or discoloration?

Thanks for the reply. I check this as one of the first things along with the visiual inspection. I also measured across the connector and it is completely flawless

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

I suspect one or more of those little mlcc caps, maybe hit them with a hairdryer then see if tv starts up if only for a bit, I knows theres a lot of them, you can check them for low ohms, unplug tv from outlet, unhook cables from mainboard to powerboard and tcon, one probe on each side, meter set to ohms, see if any are reading under 50 or so ohms or are shorted, could be a bad voltage regulator I guess?? Some mainboard testing there: https://www.youtube.com/watch?v=ocqnqmBxiqY

Thanks for the reply. I'll definately try this out later. I'll let you know how it went

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Two leds on the the tcon is suspicious. Try powering the tv with only one side connected at a time with the ribbons from the panel to the tcon.

https://www.badcaps.net/forum/showthread.php?t=80010

There was another thread on a similar model where it was fixed after finding shorted caps on the bad side.

Thanks for your message. I have tried to start the tv with everthing disconected from the main board (also without t-con) and it did not start.

I have just tested disconecting the ribbons.
Disconected both and startet with the same error
Shut down, disconected left and startet with the same error
Shut down, disconected right and startet with the same error

So no difference. I did however notice that this cable was in bad condition due to a bad assembly. (factory or previous owner - don't know). I fixed this with some heat shrink crimp (don't know the right word for it), but it made no difference. I'll need to check if this can somehow have shorted something

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Mainboard there, it's a pretty sick price tho: https://spares2repair.co.uk/samsung-...7v-bn94-06809g

Holy Moly!
This is most certainly not woth spending 220 £ on. plus shipping
That's an insane price haha

Thank you anyways. I'll save the homepage for later

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Two leds on the the tcon is suspicious. Try powering the tv with only one side connected at a time with the ribbons from the panel to the tcon.

https://www.badcaps.net/forum/showthread.php?t=80010

There was another thread on a similar model where it was fixed after finding shorted caps on the bad side.

Here's a picture of the t-con

[budwich]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Thanks for your message. I have tried to start the tv with everthing disconected from the main board (also without t-con) and it did not start.

I have just tested disconecting the ribbons.
Disconected both and startet with the same error
Shut down, disconected left and startet with the same error
Shut down, disconected right and startet with the same error

So no difference. I did however notice that this cable was in bad condition due to a bad assembly. (factory or previous owner - don't know). I fixed this with some heat shrink crimp (don't know the right word for it), but it made no difference. I'll need to check if this can somehow have shorted something

what's the cable interconnecting?

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

what's the cable interconnecting?

It is for the left speaker

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

what's the cable interconnecting?

Budwich, are you aware of any damage this might have caused?

[budwich]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

you need to post a picture of the back of the set with everything connected so the forum can see how things are connected (every set has different configurations).

As for the cable, since it is going to the speaker, it might not have caused much / any issue. Having said that, it is some what unlikely that the audio portion of the main board has a lot of protection built in since a probably assumption of the design is that the audio section of the set is "closed" and hence the design is limited to well known conditions. It is possible that a short may have taken out the audio amp and / or subtending driving voltages which if shared by other components sub-systems, might be an issue (ie. things like a common 3.3v, 5 v logic level, etc).

You need to verify that voltages on the main board are there.

[budwich]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Here's a picture of the t-con

there should also be a third led. double check the voltages that those leds are referring to... not the led itself but the labeled voltage.

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

there should also be a third led. double check the voltages that those leds are referring to... not the led itself but the labeled voltage.

Took me a moment to locate it, but you are indeed correct.
There is a third LED, which is not coming on.
The LED's which are on drag 2,65 volts whereas the third only got 1,18.
I can't find any schematics for this exact model, so I'm not sure about the voltages around should be.

I get 12,5 after the fuse on t-con
and and 3,3 acround some of the mlcc caps close to the led, which sounds reasonable

[budwich]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

From my limited experience, it is likely that the third led is indicating a problem. That voltage is usually associated with the panel in some form.

some questions: some sets (eg. sharp) when in an error state need to be forced on with some form of buttons and powering to cause the system to "limp" around the failure to allow things like access to service menus, etc. Not sure if samsung has such operation, but it might / should. The reason why I state this, is that your test of the disconnecting the tcon to panel cables, results in the same result, error and no screen response. This is somewhat unexpected. You might need a force on sequence.

Further, the third represents a "panel voltage"... you should be able to find the corresponding voltage test point. Again, it is not the voltage at the LED... its somewhere on the board.

Still further, it is likely that this set does not have side tabs and as such, you might be able to use a method referred to as "tape cutoff" (among other things) which uses a bit of tape to "cutoff" the signals going from the tcon to the panel. Depending on the fault, it allows the set to operate in a "normal" fashion thereafter. Search / read around this type of save method. You are potentially going to find that where the voltage identified by the third led, is some where in the tcon to panel cabling (usually around one edge side... 5-10 pins in or so). IF the areas is blocked, your set may function.... maybe.

here is one example: https://www.badcaps.net/forum/showth...light=blue+led

[budwich]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

Took me a moment to locate it, but you are indeed correct.
There is a third LED, which is not coming on.
The LED's which are on drag 2,65 volts whereas the third only got 1,18.
I can't find any schematics for this exact model, so I'm not sure about the voltages around should be.

I get 12,5 after the fuse on t-con
and and 3,3 acround some of the mlcc caps close to the led, which sounds reasonable

As for "design voltages", just start measuring (carefully) any labelled points that "look" like a voltage point.... eg. VCOMXXX is probably some form of common voltage used in the panel. There are others labelled on the tcon.
List them in a "table". It will be likely that some will "jump out" as being of concern.

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

As for "design voltages", just start measuring (carefully) any labelled points that "look" like a voltage point.... eg. VCOMXXX is probably some form of common voltage used in the panel. There are others labelled on the tcon.
List them in a "table". It will be likely that some will "jump out" as being of concern.

So I've been through the bunch and attached the measurements

TCON_READY is 0,00V, which I find a bit suspecious. Maybe I'm lucky and it is just a dead T-con.
I still can't emergency start the tv no matter what I unplug or reset. The internet doesn't seem to know of any "safe boot" for Samsung tv's

The chip under the heat sink gets hot as well, even if the tv is never really booting up. the plate is maybe a little warmer than body temperature

[Repair_dane]

Re: Samsung UE55F7005STXX - 5 blinks, screen dark

As for "design voltages", just start measuring (carefully) any labelled points that "look" like a voltage point.... eg. VCOMXXX is probably some form of common voltage used in the panel. There are others labelled on the tcon.
List them in a "table". It will be likely that some will "jump out" as being of concern.

I'll just try those pictures one more time