Samsung LE32R87BDX Power cycling

[Davy]

Hi,  have a Sammysung LE32R87BDX this is power cycling 'as of it wants' with kinda crackle.

The power supply voltages seems OK, I noticed if I disconnected the loudspeakers the TV would come on but with very distorted screen full of lines and the cycling not being as bad.

I suspect the main board as something in the 'screened can' possibly the CPU get pretty warm after a minute or two, would I be right or is there a cure?  Me thinks this was a Pound Shop telly.

Dave.

[Turnip]

Hi Davy,

Don't know about the sound, but the screen full of lines makes me think of the AS15 chip on the T-con that gives problems on this Sammy, though it's usually solarisation.

Don't suspect the AS15 chip can give other issues but suggest that high ESR PS caps cause a lot of problems to the Eeprom on the SSB - Chris.

[downunder]

Hi Dave,

See if this attachment fits your main board.

Bruce

[Davy]

@downunder, thanks Bruce for the link I've filed it for future reference.  The board is a BN44-0191A. I'll have a peep for any SMD capacitors all the same. The voltages seems OK and can't see any hash.  Yes Turnip, I thought it was the T con too because when I disconnected the speaker plugs the 'liney' picture came up seemed to indicate a T con fault, changing the Tcon didn't help.

What baffles me, why should unplugging the speakers cause the screen to come up and not trip as less? The AF output chip isn't warm and I checked all the speaker coupling components. It does it with other plugs disconnected too....including the inverter supply and  plug.

I've checked the dc-dc converter on the main board and that's working just fine. I do feel the casing surrounding the CPU appears to run too warm for my liking, I've not had it off yet.... maybe something is clogging a bus line up? 

Dave

[zomikula]

HAve you checked the 2 1000uf 10v caps below the metal shielding ?

If these are going out they will not have capacitance of 1000uf
and can cause strange sound issues through speakers and the power cycling

[Davy]

Hi zomlkula, sorry for the late reply. I tried your advice and still the same I'm afraid, the two SMD 1000u, 10v types.

I was advised to try IC1804 on the main board as it causes the problem described. I was told this AFTER 'having a toot' under the screening can and had already put it back - so looks like it's going have to wait a day or two until I get my new gardening tool..... 'aroundtoit'  Must say thing's looked pretty much cooked under there, the plate is also used as a heat sink on two chips coupled by two  large blocks of what looks like spongy foam with oily stuff between it and the chips - not greasy as I would have expected, the blocks are pushed firmly against the chips.  Seen some heat sinks in my time but not foam or whatever it is, oxide coated maybe.

I'll report back should I manage to fix it, Dave.

[Davy]

Replacing the Eprom IC1803 did help with the power cycling.  The Eprom can be reset by switching the set off, shorting pins 5 & 6 with longish leads, switching ON then undo the short, in my case this trick didn't work.

I reduced the power cycling, the set would then switch OFF and ON (it wouldn't before), the picture was all lines, on-screen display box full of lines popping up by itself & no sound.... I scrapped it.

The main board was singled out as the problem - I did keep the good parts. After all, the CPU appear to run 'unusually warm' for my liking.

zomikula suggested earlier I changed the two SMD 1000uF caps. outside the screening can.... I changed them and two more that was inside to be sure.

Thank you everybody for helping,  Dave

[imran khan]

http://electronics-tricks.blogspot.com/
For repair help topics

[downunder]

Hi Dave,
Thanks for reporting the outcome. Sometimes, you just gotta let go.

Bruce

[Davy]

The Tcon connector lead or Tcon board CAN result in power cycling like this with Samsung tellies.... but not in my case.

Sure had me beat, the psu voltages were within spec and hash free, all the main board regulators were up and running - except no back-light ON control.... they worked OK when 'forced' ON, I even tried a new Eprom, the CPU was running much warmer than normal I would say.

Still puzzled why the screen would come up when I disconnected the speakers, the power cycling still continued though but not as bad.... it wasn't the audio chip either?

Dave