Strange behavior when turning on my Samsung LN40A550P3F 40" HDTV

[aeneas]

Based on my limited past experience along with other reports this is a common problem with Samsung (and possibly other brands of) TVs. When turning the TV ON, it takes a long time and seems to cycle through various peculiar states before it will operate properly. I've also had this same problem with a slightly older Samsung 40" HDTV. In the prior case, it was pretty easily repaired by replacing blown out capacitors on, what I think, is called the Power Supply Board. In that prior case the bad capacitors were pretty easy to identify by swelling that was conspicuous on the top of cylindrical tubes. However, for the current case there is NO apparent swelling of that kind on any of the cylindrical capacitors (photos attached).

On the other hand there is something that looks very strange which can also be seen in the photos. Many of the capacitors, as well as what look, to me, like other kind of parts are covered with a substance that has the appearance and texture of calk. At first I thought this material leaked from the capacitors which would seem to indicate a defect. However, upon closer examination, to include removing some of this material in a couple of cases, the capacitors show no sign of any abnormality.

• Might it be that this kind of material is normal? I bought the TV new and it has never been previously dismantled.
• Could this have been part of original fabrication? If so looks to have been done sporadically.
• If abnormal what caused it?
• Is it possible that this is causing the problem turning the TV on?

[budm]

Re: Strange behavior when turning on my Samsung LN40A550P3F 40" HDTV

Bad cap can look normal but it can have high ESR.
Those white stuff is juts for holding parts in place during soldering process.
What kind of Voltage testing have you done on the power supply board?

[nomoresonys]

Re: Strange behavior when turning on my Samsung LN40A550P3F 40" HDTV

If you have a multimeter you can do test #3 below, try to do it just as instructed, you can also use a hairdryer to heat up the powerboard, heat the board a small section at a time including the capacitors the round ones and the little blue ceramic capacitors too, it's usually one of the round electrolytics, see if it comes on any faster or if there's any change.

[nomoresonys]

Re: Strange behavior when turning on my Samsung LN40A550P3F 40" HDTV

As always BE VERY CAREFUL when working with the powerboard, the HOT SIDE HAS DEADLY VOLTAGES, just a warning for anyone who might be looking on and not be aware.

[Davi.p]

Re: Strange behavior when turning on my Samsung LN40A550P3F 40" HDTV

Those white blobs are normal, Korean workers earn few moneys so they watch porn when manufacturing boards..... it's a joke...
When the tv is abs. cold, do warm up enough the mainboard with hairdryer then wait some seconds then switch on the tv, if it starts flawlessly then some electrolytic cap on the board is gone...

[Unspun01]

Re: Strange behavior when turning on my Samsung LN40A550P3F 40" HDTV

This does not sound like a power supply issue.

This is a mainboard issue common to A-series Samsung LCD and plasma TVs.

I think you need to replace C102 and C131 on mainboard, adjacent to white 24pin connector.

Both caps are polarized surface mount caps. C131 is on the top and C102 is on the bottom. Marking C131 easy to spot. Marking C102 may be difficult to find, but capacitor should be next to IC101.

Measure the voltage across the capacitors before removing the capacitors. They have a polarity marking, but it is opposite to what you think. I think the band indicates positive which is not consistent with other can type electrolytic capacitors. Installing electrolytic capacitors backwards by accident may cause them to blow up.

I think I used 47uF/50V caps.

See this thread for more information:

https://www.badcaps.net/forum/showth...ight=C102+C131