View Full Version : Year-old Samsung 50" Plasma - No Power


YamahaFreak
11-03-2014, 07:17 PM
My friends found a Samsung PN51F4500A(FXZA) 50-inch plasma TV recently, and I have been tasked with the repair attempt. It was built in September of 2013, so just barely a year old. When I plug it in, the red standby LED turns on. If I press the POWER button (on the remote or on the set) the standby LED goes out...and nothing else happens. It's like the set was unplugged. There is no evidence of physical damage, screen doesn't appear to be cracked, everything inside looks good, nothing burnt/fried, etc. No strange sounds...in fact, no noise at all. There is no info online that I could find about this model having issues. Apparently it's last year's entry-level Samsung plasma TV. No 3D or smart functions.

drussell
11-04-2014, 11:44 AM
... Samsung PN51F4500A(FXZA) 50-inch plasma ... built in September of 2013
...
When I plug it in, the red standby LED turns on. If I press the POWER button (on the remote or on the set) the standby LED goes out...and nothing else happens. It's like the set was unplugged. There is no evidence of physical damage, screen doesn't appear to be cracked, everything inside looks good, nothing burnt/fried, etc. No strange sounds...in fact, no noise at all.

I'm also working on a recent Samsung Plasma today, a PN60E530A3F built in January 2013. I ended up bringing it back with me to do more sleuthing as when I checked most of the obvious stuff on-site (in case it was something easy like no voltage due to a blown-up capacitor or other typical Samsung-y problem) but everything I checked seemed fine. This is a bar TV so it sees high hours but the thing isn't even two years old yet (!!) AND by the look of the screw heads and one broken plastic stud, I'm pretty sure someone's been in here before already to repair! Not a good omen! This set just does 6 blinks on a cold-plug-in start attempt then locks out.

As for yours, have you checked the power supply voltages? On most plasmas the power will attempt to come up briefly on plug-in. Check your VS and VA from the power supply and make sure you have low voltage (on most Samsungs thats something like +5.3v and +15v). Do you have voltage (briefly) on all of them at plug-in or power button press?

If you have VS and VA then you can start to check for VScan / Ve, start looking for X or Y board problems, etc. If you don't even have VS and VA and your low voltages, it's going to lock out immediately so that needs to be fixed first.

Celt
11-04-2014, 04:57 PM
Yes...check power supply voltages first...and look for bulged caps. :yes:

drussell
11-04-2014, 07:03 PM
Yes...check power supply voltages first...and look for bulged caps.

It's unlikely to find bulged capacitors in such a low-hours set. Generally if a capacitor that new dies, it shorts or opens without any external physical symptoms. (He also stated that he didn't see anything burned/fried so I would think that includes crusty capacitors.) :)

YamahaFreak:

I also forgot to mention, check the obvious, like fuses... The main AC input fuse must be good to be getting the red light but there are usually at least a couple small surface mount ones on the logic board.

Speaking of the logic board, Samsungs usually have a green LED on them. What is yours doing? It should sit there and flash with a period of about once per second if everything is normal.

The problem with this one here turned out to be a couple of shorted FETs (actually IGBTs, but whatever) on the Y-Main board... I'll have to order some from Digikey tomorrow since they are fancy super-high-current (220A), high speed switchers specifically designed for use in pulse applications in PDPs (like the ERC) so none of the usual stuff I have laying around is going to come even close to surviving in that circuit.

NJRoadfan
11-05-2014, 04:31 PM
The problem with this one here turned out to be a couple of shorted FETs (actually IGBTs, but whatever) on the Y-Main board... I'll have to order some from Digikey tomorrow since they are fancy super-high-current (220A), high speed switchers specifically designed for use in pulse applications in PDPs (like the ERC) so none of the usual stuff I have laying around is going to come even close to surviving in that circuit.

Funny, thats the same circuit that usually fails on late model Panasonic PDPs. I wonder if insufficient cooling has something to do with it. Many of the earlier panels with fans don't seem to have FETs blowing up on them.

Celt
11-05-2014, 05:21 PM
It's unlikely to find bulged capacitors in such a low-hours set.

A 2013 set could very well have bulged (damaged) caps. Last year I replaced several caps in a 6 month old Sony DVD player.

YamahaFreak
12-16-2014, 12:46 AM
Well, unless there is a cost-effective, non-warranty method of getting a replacement plasma panel, this set's toast. The owner's dog knocked it over and cracked the screen! :thumbsdn:

Electronic M
12-16-2014, 01:08 PM
Unless you can find the same set with a good panel and ruined boards...Stick a fork in it, it's done.

CoogarXR
12-16-2014, 03:23 PM
Did you ever fix it? If so, check if the boards are worth anything on ebay before it hits the dumpster ;)

Unless it was on when the screen was broken (or was attempted to be turned on after the screen was broken). This will blow the Ysus and/or buffers on some models.

YamahaFreak
12-16-2014, 06:15 PM
No, the set has not been plugged in since it was cracked. That's probably what I'll end up doing - parting it out and trying to sell the boards. *sigh*