Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

[Unspun01]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

It is a Z3018.

Looks like an AOpen AOZ3018PI.

See attached datasheet. 5A buck regulator. Could be bad.

If you don't have a Z3018PI (5A buck regulator), you could try a Z3013PI (3A buck regulator, same pinout as Z3018PI) in its place temporarily.

Not saying this is your problem, because you still don't have VIN to those chips, but may assist you.

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

Every single surface mount capacitor is important to troubleshoot this way.

What do you think about that group of SMD caps under the processor EDIT/ADD all indicating short?

[Unspun01]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

smd caps near large processors are a funny animal. Sometimes the CPU lines are such low resistance that they may appear as a short.

Double check if they are truly a short (0 ohm), or if they are just really low resistance (like 5 - 7 ohm).

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

Looks like an AOpen AOZ3018PI.

See attached datasheet. 5A buck regulator. Could be bad.

If you don't have a Z3018PI (5A buck regulator), you could try a Z3013PI (3A buck regulator, same pinout as Z3018PI) in its place temporarily.

Not saying this is your problem, because you still don't have VIN to those chips, but may assist you.

From what source does Vin come from? I haven't been able to trace it out.

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

BTW, those 3-pin devices (3 of them) with big metal with center pin trimmed off, can you read P/N and Voltages on all 3 pins?

They are LD1117AC, looks like a linear voltage regulator. There are two and both have zero voltage at any pin. The last one is 17-33z 1332AG, also no voltage.

smd caps near large processors are a funny animal. Sometimes the CPU lines are such low resistance that they may appear as a short.

Double check if they are truly a short (0 ohm), or if they are just really low resistance (like 5 - 7 ohm).

There is about 1.5 to 3.5 ohms resistance across those caps.

Also, VIN on IC208 (AlphaOmega AOZ3018PI) appears to be directly connected to both B5V terminals at the power board.

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

After doing ohms checks on those 3 regulators one of them has 155ohms resistance to ground on the pin indicated. The others all check open.

EDIT/ADD: According to the datasheet the pin with low ohms is VIN

[budm]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

I expect one of those 3 linear regulator input pin to be connected to 5V Standby.
The B5V is the switched 5V that will not be present until the PS-ON is present.
So far no luck finding the schematic for this main board yet.

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

I expect one of those 3 linear regulator input pin to be connected to 5V Standby.
The B5V is the switched 5V that will not be present until the PS-ON is present.
So far no luck finding the schematic for this main board yet.

I measured resistance from the A5V pin at the connector to each of the VIN legs on those regulators. The amount of resistance was 7K to 14Kohms and I had a reading on all three.

[budm]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

Can I see closed up pictures around the connector where the A5V pins are to see where the traces go to? This is tough troubleshooting without the diagram. May be there is inductor between the In pin of the regulator and the A5V that has gone open circuit. I also expect the 5V to be regulated down to 3.3V, 1.8V to run the processor, IR receiver and the button board.

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

Can I see closed up pictures around the connector where the A5V pins are to see where the traces go to? This is tough troubleshooting without the diagram. May be there is inductor between the In pin of the regulator and the A5V that has gone open circuit. I also expect the 5V to be regulated down to 3.3V, 1.8V to run the processor, IR receiver and the button board.

Ok here's pix of the connector area. If you look under the connector you will see a circled X. The connector block covers the traces on that side of pins so I tested for continuity from the A5V pin to several areas near the connector and this is the only place I got no resistance.

Also included a pic of the back of the board but it looks like the trace for that pin may be on the top side of the board.

[budm]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

https://www.badcaps.net/forum/attach...8&d=1550294594
I do not quite follow you, looking at the top side of the board you can see the odd number pins, which one are for the A5V.
I can see lots of inductors connected to power pins:
1-3
5
7-9
11-13
I also see black fuse F201 with 'Y' printed on top sitting next to R201 which has one end connected to pin 1 of IC201.
There may be more fuses on that board.
BTW, post 4 was asking about IC201 (SMPS IC) but your post 5 you refereed to IC1201.

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

https://www.badcaps.net/forum/attach...8&d=1550294594
I do not quite follow you, looking at the top side of the board you can see the odd number pins, which one are for the A5V.
I can see lots of inductors connected to power pins:
1-3
5
7-9
11-13
I also see black fuse F201 with 'Y' printed on top sitting next to R201 which has one end connected to pin 1 of IC201.
There may be more fuses on that board.
BTW, post 4 was asking about IC201 (SMPS IC) but your post 5 you refereed to IC1201.

I found the fuse and it tests good.

IC1201, pin 22 is where I found the 5V stand-by voltage. From that point there is no voltage I can find anywhere.

I'm going to add a picture of the call-out on the power supply for the pin assignment. If you look at the board the odd number pins is the flat jacketed harness on top and the even number pins is the flat jacketed harness on the bottom. The orientation is the same at the main board.

EDIT/ADD: removed

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

https://www.badcaps.net/forum/attach...8&d=1550294594
I do not quite follow you, looking at the top side of the board you can see the odd number pins, which one are for the A5V.
I can see lots of inductors connected to power pins:
1-3
5
7-9
11-13
I also see black fuse F201 with 'Y' printed on top sitting next to R201 which has one end connected to pin 1 of IC201.
There may be more fuses on that board.
BTW, post 4 was asking about IC201 (SMPS IC) but your post 5 you refereed to IC1201.

In the absence of a schematic for this board I attempted to put together a somewhat hi-res combined image that is hopefully large enough to be helpful. I'm going to have to re-do it but maybe this is a start?

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

So far no luck finding the schematic for this main board yet.

Another attempt at a better combined image, the whole top of the board and where stand-by is present.

[Dannyx]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

The part toward which the arrow is pointing looks like the MICOM....could be wrong though. Others are free to correct me on this. Really interested to see if you can fix this, would be very informative for the future.

[nomoresonys]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

Repair kit there, maybe check those components, says "complete" repair kit but who knows. https://www.shopjimmy.com/samsung-bn...repair-kit.htm

[Dannyx]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

I believe his PSU is working fine, but still worth double-checking I guess...

[nomoresonys]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

Oops, crap I thought he was working on the powerboard, need coffee still sleepwalking.

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

The part toward which the arrow is pointing looks like the MICOM....could be wrong though. Others are free to correct me on this. Really interested to see if you can fix this, would be very informative for the future.

I'm pretty sure this is correct, could it be a sub-MICOM? The description of this chip is Flat Panel Display Control Sub-MCU. I hope we can fix it too!

Repair kit there, maybe check those components, says "complete" repair kit but who knows. https://www.shopjimmy.com/samsung-bn...repair-kit.htm

I believe his PSU is working fine, but still worth double-checking I guess...

I believe the PSU is working fine since I found 5VSB at that sub-MICOM controller

Oops, crap I thought he was working on the powerboard, need coffee still sleepwalking.

I used to love Coffee, but after years it was making me have to pee every 10 minutes! Now I drink Pepsi.

[DXseekerMO]

Re: Samsung UN55F6300AFXZA appears dead, stand-by present, main board suspect

https://www.badcaps.net/forum/attach...8&d=1550294594
I do not quite follow you, looking at the top side of the board you can see the odd number pins, which one are for the A5V.
I can see lots of inductors connected to power pins:
1-3
5
7-9
11-13
I also see black fuse F201 with 'Y' printed on top sitting next to R201 which has one end connected to pin 1 of IC201.
There may be more fuses on that board.
BTW, post 4 was asking about IC201 (SMPS IC) but your post 5 you refereed to IC1201.

When budm stops talking, I start re-checking my work LOL! Indeed I have made a mistake.

The 5V present on the power supply at all times is in fact A5V, not B5V.

B5V is only present when the main harness to the main board is unhooked from the PSU. Otherwise it is absent. This has been confirmed and I am certain of these new findings.

So either B5V is being eaten by a short on the main board or in fact I have a PSU problem.

You all have my sincere apologies. I actually hope its the PSU since I stand a way better chance of fixing it than a main board!

So here's a question I added: Can I de-pin the B5V terminals from one of the connectors to see if the voltage returns at the PSU? If it does this would confirm a short on the main board?