Samsung UN55FH6030: random power cycling

[valvashon]

Samsung UN55FH6030, perfect size for my office and does OTA well but isn't a smart TV. That's OK because I am a TV station engineer and only need it for OTA monitoring.

About a month ago it started power cycling itself once or twice a day and now it's nearly continuous once it's been on for a few minutes. Changing channels would really start it cycling and it would take several minutes to stabilize but now it's just doing it almost non-stop without changing channels.

Once I disconnected the antenna I found that I could change channels with no issues. My guess is that the rest of the circuitry is drawing power at a level that, when a signal is received, throws the power supply into instability. I have not tried putting a signal into a different (like HDMI) input.

Opened it up and did not see any blown capacitors in the power supply but that doesn't mean the caps in there are good. Board is the PD55CV1_CHS/BN44-0556A. Any known issues with this board or should I just start pulling caps and testing?

I'm positive that this is a power supply issue as I have the TV set to automatically turn on in the morning and off in the afternoon. This power cycling erases that setting as if it had been unplugged.

Thanks

[nomoresonys]

Re: Samsung UN55FH6030: random power cycling

Heat the electrolytic caps with a hairdryer for a couple minutes, then try it while it's still hot, just in case it's a marginal cap.

[EazyBone]

Re: Samsung UN55FH6030: random power cycling

Take back off, stick multimeter on the 12v line or whatever to the main board see if voltages start to drop or are steady. They shouldn't fluctuate at all. I'd do this before trying to pull caps off. You can also just use multimeter to test main caps and just look for fluctuating voltages. If you say it happens very quickly then you won't have to wait long. And if it's fluctuating then you know it's likely the PSU.

[KYBOSH]

Re: Samsung UN55FH6030: random power cycling

I think the two maestros above are on the right track.
Let me throw in another possibility although improbable bcos we are dealing with LCDs.
The power supply on plasma TVs would develop bad/dry solder joints after a decade or so.
Those TVs were power hungry and worked the power supplies hard. The power supplies were not lightweight by any means but the weak links are always the solder joints, the caps and the FETS. Not necessarily in that order.

Check for dry solder joints while you are doing your inspection. When they are bad they can look really bad but they can also be innocuous looking and still cause a bad behavior.
Look at the transformer especially.

While I have never come across this issue with LCD TVs this TV is old enough to warrant a look.

As a matter of good housekeeping I like to simply touch up (melt/reflow) all joints on old boards with my soldering iron and a dab of solder. This TV is just 10 years old and LCD so its probably not a major issue but it doesn't cost or hurt anything to do this and at least you would have easily eliminated a potential source of the problem.

Good luck and keep us posted!

[nomoresonys]

Re: Samsung UN55FH6030: random power cycling

I think the two maestros above are on the right track.
Let me throw in another possibility although improbable bcos we are dealing with LCDs.
The power supply on plasma TVs would develop bad/dry solder joints after a decade or so.
Those TVs were power hungry and worked the power supplies hard. The power supplies were not lightweight by any means but the weak links are always the solder joints, the caps and the FETS. Not necessarily in that order.

Check for dry solder joints while you are doing your inspection. When they are bad they can look really bad but they can also be innocuous looking and still cause a bad behavior.
Look at the transformer especially.

While I have never come across this issue with LCD TVs this TV is old enough to warrant a look.

As a matter of good housekeeping I like to simply touch up (melt/reflow) all joints on old boards with my soldering iron and a dab of solder. This TV is just 10 years old and LCD so its probably not a major issue but it doesn't cost or hurt anything to do this and at least you would have easily eliminated a potential source of the problem.

Good luck and keep us posted!

+10, great advice.

[valvashon]

Re: Samsung UN55FH6030: random power cycling

Thanks for the help on this one everybody. I opened the unit up and checked the voltages; they were stable. I heated up the caps and the board gently with a heat gun, no shutdowns noted. I then pulled the board and touched up a number of solder points including transformer connections and cap connections. Put the unit back together and no shutdowns noted. Wrapped the thing in a blanket, no shutdowns noted.

It's as if pulling off of the wall and taking down the hall to the shop fixed it. It's been back on the wall for close to if not two weeks working normally with no shutdowns. I know this because it turns on and off at the scheduled time so there have been no power interruptions in the unit. Scratching my head on this one, I must have done something to fix it but I'm not sure what.

Here's hoping the problem won't come back.

Val

[lotas]

Re: Samsung UN55FH6030: random power cycling

Try performing a Factory reset in service mode.