Samsung LE46M86BD Constant Restarting

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

Maybe when removing the cover shield the heat has made the faulty capacitors work tempory hence why we use a hair dryer to heat the boards to aid our fault finding etc a problem like this will come back and start playing up again, if your running the set without that heat shield on remember it acts as a heat sink as well for some of the chips so dont run it for long.

May be something to do with that. The symptoms of this set are a bit different though.

You first turn the tv on and it works fine for about 5-10 mins, afterwards it starts to turn itself off, click and then turn itself back on when power is restored. Unlike other videos and descriptions online of Samsung tvs doing the same thing, the screen flashes off just the same as if you were to pull the plug. It does not go black the same way as turning it off on the front or with remote.

Then what happens is it repeats this on off sequence for up to an hour.

Off>On (for 5-10 seconds, picture shows fine)>off- rinse and repeat.

Eventually it stops and for the rest of the time after its being used it will not turn on and off again.

To simplify it, it only happens when running from cold and only after a few mins of operation.

That being said, it makes little sense why it isn't doing it now. If capacitors are overheating then surely after some time it would start happening or get worse. Not eventually just work after not touching it for a while.

If the capacitors are only functioning properly when *heating up* to a decent level then it makes no sense at all why its not doing it now.

I will use the hairdryer, but since it seems to do it when closer to a cold start I'm not sure it will do anything. Thanks a lot for your help.

[vinceroger69]

Re: Samsung LE46M86BD Constant Restarting

I wonder if its a bad bga solder joint as when things are cold they contract when there warm they expand so if it was a bad bga soldered joint it may explane it. Im still new myself as in doing repairs but i have read a fair few threads and these things can happen it may even be a bad soldered joint on the psu maybe some of the larger items ie transitors on heat sinks may have dry joints on there legs etc.Capacitors can fail by low uf readings or high esr readings etc they can give odd syptoms at times.

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

It could be, I just tried cooling the caps in the heatsink described in this thread and heating them briefly with a hairdryer when the tv was on but nothing.

Could it be dust that was causing it? The tv was horrendous inside and I've since cleaned it up.

[vinceroger69]

Re: Samsung LE46M86BD Constant Restarting

I honestly wouldnt of thought so my guess is when you removed the cover/sheild the soldering iron heat has maybe made a tempory fix, you would of had to remove the mainboard to remove that shield? maybe a bad wiring connector contact.

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

Oh yeah I've removed both boards before I even removed the heatsink. To begin with the TV was intermittent at showing this fault but when it happened it did keep happening and always close to being turned on.

I have ordered one of those esr meters and a capaticance multi meter. I'm a complete novice though so short of testing each capacitor I'm not sure what else to do.

I guess I could also test each voltage supplied to the main board.

If the damn thing is working now and I put it back on the wall I know to well it will start doing it again, it would be just my luck.

[vinceroger69]

Re: Samsung LE46M86BD Constant Restarting

That meter i linked tests esr and capatience and transistors and diodes etc they do one with test leads too so for a cheap meter there quite good. Yes you should check all the voltages on the power supply take readings when the sets working and also readings when its in the failed state just be aware there is a high voltage on the hot side of the psu and also some of the heat sinks are live too and can give you a nasty shock.

[budm]

Re: Samsung LE46M86BD Constant Restarting

We already know that the common failure on the main board is due to those SMD caps, you might as well replacing them now, they will need replacing sooner or later.

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

That meter i linked tests esr and capatience and transistors and diodes etc they do one with test leads too so for a cheap meter there quite good. Yes you should check all the voltages on the power supply take readings when the sets working and also readings when its in the failed state just be aware there is a high voltage on the hot side of the psu and also some of the heat sinks are live too and can give you a nasty shock.

Thanks. I bought one from the UK that looks the same for slightly more, just because I don't want to wait for shipping from China. It doesn't come with leads, but I can always desolder to test right?

We already know that the common failure on the main board is due to those SMD caps, you might as well replacing them now, they will need replacing sooner or later.

Would these suffice?
http://uk.farnell.com/panasonic-elec...tor/dp/2284745

Same uf but higher voltage.

EDIT# I linked wrong size. Here is linke to 8mm cap: http://uk.farnell.com/panasonic-elec...eel/dp/2408656

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

I purchased the above caps, so will wait for equipment to arrive before updating. Thanks a bunch to everyone that helped me. Really appreciate it.

[vinceroger69]

Re: Samsung LE46M86BD Constant Restarting

you can use ordinary leaded capacitors just lay them down sideways i use this shop if im stuck quick delivery and genuine capacitors
http://www.ebay.co.uk/itm/1110202690...%3AMEBIDX%3AIT

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

Think I made a mess of desoldering the two SMD caps because I accidentally pulled off one the copper strips that seemed to be glued to the PCB underneath one of the SMD pins.

I got it into place and glued it but after soldering the new ones in the TV has gotten worse. It turns on and off, but also displays flickering now.

I'm wondering if there is a way to replace those little copper tracers that seem to be glued underneath the solder of the SMD caps?

I also wonder why it happened. I wonder if its due to my soldering station not being good enough, sometimes it really struggles to desolder, especially when there is very little solder like on these caps. For one I had to add my own solder to get the ball rolling.

I tin the tip of my iron and this is the station I am using. The tip is conversantly thin which I thought would be a bonus given the nature of this work. Its not a Weller I know, but I made sure I had one above 50w. When soldering I find I have to have the temp on max @450 'c

Anyway, if I can't repair my work, should I look for a replacement board? I wonder which will be compatible, since it seems difficult to find the exact same model number.

[vinceroger69]

Re: Samsung LE46M86BD Constant Restarting

I had to bridge a trace myself the other day after i messed up replacing a eeprom chip i used a very small piece of copper wire and soldered one end to the trace that had broke and the other direct to the eeprom leg i had to use a light/magnifyer lens but it worked out ok. I always add fresh solder before i remove any capacitors etc makes it easier im my opinion, as you say its got worse maybe its not soldered correctly? did you make sure you put the capacitors in the rite way as in positive and negitive? ive made this mistake once easy done.

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

Thanks. I thought the problem got worse but I'm not sure. Using an external output it still just loses power and turns off. On the tuner it's a different story but I haven't tested that before. On the tuner input the screen moves with lines and still turns on/off.

I've desoldered a bunch of caps from the power board today and tested them. The larger ones show no esr and are in a good range of capaticance apart from maybe one 1000uf one reading 0.01esr and 847uf? The smaller 47uf ones are showing a tiny esr of around 0.37 but are testing his at 45uf.

I also desoldered two of these but I can't test them. Are they not capacitors?


I have a cap meter and multimeter now so I can test voltages too, just not sure where to start the diagnosis.

I've ran the set on and whilst it's restarting I've tried warming the section under the heatsink and around the power board with a hairdryer but nothing helps.

I wonder if it's because I've messed up the first caps I replaced or if it's just working as before. I'm not sure how to test.

[vinceroger69]

Re: Samsung LE46M86BD Constant Restarting

I think there some type of coil im sure someone more experienced will tell us how to test them what do they test at if you check them with a multi meter on ohms setting

mabe also with all the capacitors you have removed write a list of there uf values and what they now measure uf wise and esr we can have a look over your list then.
Also some samsung suffered bad eeproms that caused this kind of issue not sure if its on your set though

[budm]

Re: Samsung LE46M86BD Constant Restarting

The is just a an inductor with Ferrite core in shrink tubing, part of the Pi filter for the DC supply. LNxx.

[vinceroger69]

Re: Samsung LE46M86BD Constant Restarting

The is just a an inductor with Ferrite core in shrink tubing, part of the Pi filter for the DC supply. LNxx.

Thanks budm.

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

From the power board I removed:

2x capXon 2200uf 10v they tested at:
2127uf ESR 0 Vloss 1.9%
2141uf ESR 0 Vloss 1.6%

1x capXon 1000uf 10v:
971uf ESR 0.01 Vloss 0.8%

2x capXon 1000uf 25v:
917uf ESR 0.01 Vloss 1.3%
859.7uf ESR 0.03 Vloss 1.3%

3x capXon 47uf 50v:
48.63uf ESR 0.49 Vloss 1.2%
47.97uf ESR 0.41 Vloss 0.9%
49.27uf ESR 0.44 Vloss 1.1%

Where should I go from here? I've tried finding the service manual for the TV so I can perhaps find voltage test points but none seem available for free. The boards themselves don't have any voltage values near the power pins either. I would have to plug it all in too since I don't know where the power pins to short are. Just not sure what to do.
Thanks again.

Edit# I found a replacement main board for £30 should I just buy that?

[vinceroger69]

Re: Samsung LE46M86BD Constant Restarting

The connector voltage markings are at the bottom of the board in the picture top picture in post 33 by the white blob of glue.

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

I'm stuck again unfortunately. I soldered back the caps I removed(made sure exact positioning through a prior photo and pcb markings) and I'm back to square one. The tv is turning on and soon enough turning off and on by itself.

I've tried to test the input AC voltage that comes direct from the power but the probes on my multimeter aren't thin enough to make enough contact inside the plug for a reading.

I've also tried measuring the dc volts going into the mainboard according to the small schematic. The schematic seems to read upside down to what I would have thought but I successfully managed to read the 5.2v pin. With the lead plugged in though again I can't measure because the probes are too large.

I learnt online in order to test all pins you need to short the 5.2v pin to trick the power supply into thinking it's plugged in. I've tried shorting it but it doesn't seem to work. I can't get it to run so I can test the other voltages. What's the best way to successfully short the pin so I can test the other voltages?

Not sure what else I can try apart from replacing the main boards.

Edit# okay I've managed to measure all the DC points and they all seem to be working fine with reasonable values. Every voltage is above the labelled amount with a small enough margin. I would guess the power board is working fine on these grounds then and it's the motherboard that's causing the tv to switch off on it's own.

[Dodgexander]

Re: Samsung LE46M86BD Constant Restarting

Does anyone know what replacement motherboard I can order for this set? The markings on my board read BN94-01264B(1010(1005) but I can't find that exact board available online.

Will any similar boards work? Does it have to be exactly the same? Perhaps someone who has replaced these before can offer me a helping hand?