Samsung P50C450B1W - S/by issue.

[Turnip]

Hi Folks,

Have one where on turn on get the Sammy Fa-Da where voltages rise to normal, then set reverts to S/by. Thought check for dries on the P/S and resoldered here and there.

No obvious shorts - Wonder if anyone has ideas - Thanks - Chris.

[downunder]

Hi Chris,

Unplug the lead from PSU to Y-Main (Y-Sus). Turn it on and see if it stays on. If yes, then reconnect and unplug the lead from Y-Main to X-Main (Z-Sus). Turn it on and see if it stays on. If yes, then X-Main is faulty.

LED on Logic Board normally blinks once per second. If not possibly Main Board. Could also isolate the PSU and force it on and see if any of the LT rails fire up to prove the PSU is working. You won't get Vs as this is switched on by the Logic Board. PS-ON is 0V so you'll need to ground PS-ON to activate the power supply.

I'll upload the fast track guide for the Trump model if the forum accepts the file format.                                Bruce

[Turnip]

Hi Bruce,

Thanks for the 'Heads Up' Always thought Sammy issues were dries on the P/S as done a few. Note 'Trump' accepted on Quuq, so will check it out.

Gather he's over here in the UK soon to play golf, maybe with our Queen or Prince Phil - After he's sorted long divided countries, China exports and EU imports, giving Russia a quick slap on the way.

Seems quite a chap in his own estimation - Chris.

[Turnip]

Hi Bruce,

Did as suggested, then with the plugs in Vs / Va / Vsc / Ve were correct 'till the logic board turned Vs off. Led on logic flashes every three to four seconds - Don't know if it's significant. Low voltages on P/S are correct all the time, so guess logic senses an error somewhere - Bit complex, any more thoughts ? - Thanks - Chris.

[downunder]

Hi Chris,

I note that the fast track guide mentions that the set will turn off if Y or X main is unplugged. Could well be the main board - see if you can generate test patterns as per attachment. If so, then main is the culprit.

Bruce

[Turnip]

Thanks Bruce, will do.

Notice the logic board doesn't shut down the P/S, just the Vs. with PS low voltages still OK.

Chum mentioned that CS809 (68n/1250) can go O/C (top centre power board) and CS401 (Small Blue ceramic under heat sink RHS) on Y-Sus can go S/C - Not my problem though, but might be useful - Chris.

[downunder]

Hi Chris,

Yep, Main activates PSU via PS-ON and logic board activates Vs via VS-ON. Were you able to get test patterns going?

My gut feeling is that the main board is at fault, given that the Logic board LED is giving wrong code.                    Bruce

[Turnip]

Thanks Bruce,

Didn't realise the logic board Led had a code as suspected a flash every three seconds might be normal.

Note that on Ebay, every panel for this set is really cheap, except screen, speakers, stand screws, mains lead and the genuine RCU.

Have ruled out speakers and RCU. screen seems pretty well OK, so think go for the SSB as first option - Chris.

[Turnip]

Hi Bruce,

Forgot to mention tried the Test Pattern biz, but as Vs from logic shuts down (3v to zero) in a couple of seconds (other P/S
voltages OK) don't get any display.

Guess logic checks for error most everywhere, seems most errors don't knock off Vs judging from pictures on the 'fast track'

Out of interest, if screen damaged (Looks OK) would logic cut the Vs, as suspect air in the panel would prevent operation ?

Many thanks - Chris.

[downunder]

Hi Chris,

In my experience, a cracked panel always takes out the buffer boards, and possibly the Y-main. Are you able to try the TV with the buffers removed from the Y-main.

Another thought, since a lot of error signals from scan circuits are routed via the logic board to the main, why not try removing the flex that goes from Y-main to logic, and see if the LED on the logic returns to 1 blink per second. May indicate a faulty Y-main.

Could try forcing Vs on but will likely create more mayhem than currently exists. I hate these sort of faults where only solution sometimes is to keep throwing replacement boards at the unit. See how you go.

Bruce

[Turnip]

Hi Bruce, thanks a lot.

Cust has donated the set, but naturally without the stand as such folks throw 'em away where they turn up on Ebay for 50 Quid or so. Chap not dismayed as didn't want to spend anything much. Offered him my nice 50 inch Pana where the Ysus IGBTs had gone pop due to earthing issues, but £100 was a bridge to far, even with the stand, and rather newer than his Sammy.

Will check your suggestions, as hate dump a decent set. Also plasma stack nicely against the workshop wall, taking little space.
Just got a cheap stand for a 60 inch LG with a Y-sus IGBT issue - Just have to mend it - Chris.

[Turnip]

Hi Bruce,

Did as you suggested, where disconnecting flexy Y-sus to Logic gave me a one second logic Led flash - Hopeful. Tried without the buffers with flexy in - 3 second flash so guess a Y-sus issue.

To Ebay where most every board is incredibly cheap - Working Y-sus for under a tenner inc post - Guess there are a lot about, as seems no one tries mend sets these days - Thanks again - Chris.

[downunder]

Hi Chris,

That's sounding hopeful. I always encourage punters to have plasmas repaired, more for selfish reasons than anything else. They do give a glorious picture. Sourcing the boards is the biggest hurdle and I don't always have a win.
Bruce

[Turnip]

Hi Bruce,

Got 'screen smash' Y-sus board £8.50 inc post. PS clicked, squawked then turned itself off. Checked Vs to deck - S/C. Price is pretty normal over here, so there must be good ones about as there's dozens of 'em on Ebay.

Needed a screen, so to a supplier who had one from a 'screen smash set' - Queried, where he said it was a typo, and send me a really nice screen for a small Lap-Top where I wanted LTA216AT01 where kids had knocked it over then poured sugar loaded juice over it causing almost perfect circular patches here and there - Still looking. Tried a presumed equivalent where it fitted perfectly but the picture looked a bit odd, bit like an Eeprom issue with sets which don't have the famed duff chips on the T/con. Guess swapping stuff has issues, can't win 'em all - Chris.

[downunder]

Hi Chris,

A smashed screen will never do if (A) it was smashed while the set was running or (B) the set was turned on after it was smashed.

It's a tough life.                                   Bruce