SAMSUNG PN51F5500AF 231v vs

[bman4]

i have a Samsung plasma that i was told had no life

when i got it would flicker the panel but eventually took out the y main while testing.

i thought maybe bad caps on y main or x main so bought them used.

now that i look i got a standby light and the panel flickers and seems to illuminate since i look closely now but goes into protection reboot loop.

i tested all voltages and thought they where fine because i seen va 58 and vs 208.

now that i monitored voltage fluctuation closely, ive come to notice that vs shoots up to 231 then 208 and continues down ,the pot dose not seem to induce any changes, possible bad pot?

i decided to start testing without the board connected and these where the results i got above.

y main shorted but not my previous x.

i was lucky enough to catch this before shorted new ones.

will these voltages do damage?

my va is 58 right on but i got a problem with vs side.

any idea what caused this on a smps Samsung BN44-00600A P51FF_DSM, PSPF361503A


i notice two green thermistor NT802S. sgk2r58 that are brown on the board near the legs on the psu. i tested them and get 120 volts on each side , shorted?

my guess was cold solder because they are bad looking then i discovered vs is bad .


im guessing new psu,have exhausted my funds already on trying the quick fix approach. it might be time to send these boards back and try to take my time and component repair.

i cant rember how to use my own images but mines is significantly darker

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

i do get a reading from the pot.

when i turn it up to 18 ohms i get 234 an when i turn it to 0 i get 231-229.

i tested the pot and it gets a reading from 18 to 0 so i think its working.

im guessing something is leaking 230 volts from a short component.

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

after some much needed sleep after a night of none i came to a conclusion.

at this point i feel if i did damage them from my psu then that's on me.

i would rather take the loss and have a spare back up set of boards and sell them my self in the future then screw around a good seller.

i think something in the voltage regulators has gone or something in the circuit communicating to them.

i did hear one of the components clicking when my vs shorted on the big heat sink but still believe the culprit is on the right side of white line.

i was trying to convince myself to take my time and fix them myself but just wanted to watch it so bad.

i had a feeling this power supply was the culprit but convinced my self that since i seen 200 volts that it was instantly good.

yet another lesson learned that you get good vs this dose not mean the battle is won and to always make sure it's not over.

watch out for this model of smps because it's fully capable of failing and taking out y main.

my xmain did not short like y main so i have hopes it's fine.

first step is a cap tester and figure out the shape of all these sam wah caps.

i ordered a lcr meter from tomtop.wholesaler and have yet to receive one a year later but he is still communicating !

http://www.ebay.ca/itm/M328-LCD-1286...tfrom=30637516

sincerely,
bman4

[tom66]

Re: SAMSUNG PN51F5500AF 231v vs

Make sure to lock your multimeter in the highest range if it is autoranging. 231V could just be overshoot on the autorange mode.

To do this, usually you would press RANGE to select the desired range.

I would not expect a transient of 231V to damage a Y-main, although it is not a good voltage to have while the set is operating.

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

[QUOTE=tom66;763412]Make sure to lock your multimeter in the highest range if it is autoranging. 231V could just be overshoot on the autorange mode.

To do this, usually you would press RANGE to select the desired range.

I would not expect a transient of 231V to damage a Y-main, although it is not a good voltage to have while the set is operating.[

my meter is a old i don't think it had auto ranging, time for a new meter!

i get a stable voltage on va of 58 .

i going to fire it up with out the main board and see what steady voltages and possible smoke i get.

thank you,
bman4

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

i fired up the psu on bench and let the voltage sit and it eventually got up to 253!

i fluctuates from 229- 253 up and down, took a bit to get up to 253.

i still got 239 with the boards connected!

wow no wonder y my last y main is shorted when left it on long enough!

its a dam shame there is no fuses on the x a y mains any more.

im guessing shorted voltage regulators.

it's between get a new psu and wait for more funds or get a tester and buy parts which could take a long time from asia, decisions, decisions.


i hope my x and y are still good they might prematurely fail now.

well im still alive so i got that going for me .

thanks bad caps,
bman4

[tom66]

Re: SAMSUNG PN51F5500AF 231v vs

Yeah, 253V will kill something.
Fuses wouldn't do anything. The fuse blows after the semiconductors fail, it doesn't actually save the board. I've never had a plasma Y/Z-sus board with a blown fuse that didn't have other faults.
You can test the new PSU with two 120V lightbulbs wired in series (or a 240V one if you can find one)

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

Yeah, 253V will kill something.
Fuses wouldn't do anything. The fuse blows after the semiconductors fail, it doesn't actually save the board. I've never had a plasma Y/Z-sus board with a blown fuse that didn't have other faults.
You can test the new PSU with two 120V lightbulbs wired in series (or a 240V one if you can find one)

i only got ccfl florescent 120v. off to find some accent incandescent .

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

how many watt light bulb ?



im getting some mini 3 leg smd fets not reading on one side on the bottom

getting rising number , none , good diode,both way reading in circuit.

i gotta get a new tip for soldering iron then i can start puling and testing.

[tom66]

Re: SAMSUNG PN51F5500AF 231v vs

100 watt if you can get them, that's representative of an average picture load on the PSU.

What's the BN44... number on PSU... Maybe able to get schematic. Also would need number on those parts to say what they do. If I were a betting man I'd look at the optocoupler and feedback ckt, but difficult to diagnose if you don't understand it in detail.

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

100 watt if you can get them, that's representative of an average picture load on the PSU.

What's the BN44... number on PSU... Maybe able to get schematic. Also would need number on those parts to say what they do. If I were a betting man I'd look at the optocoupler and feedback ckt, but difficult to diagnose if you don't understand it in detail.

only got 60 watts , what about 2 pairs in series ?

board number is :Samsung BN44-00600A P51FF_DSM, PSPF361503A


the legged fet qs806 = lnw 31 seem to be a part of the top optocoupler circuit.

qs806 = lnw 31. it's the top one near optocoupler with board facing direction of picture, top pin has no reading either direction while bottom dose.

pcs8025 817b. good diode reading both ways on dc side.

i know a optocoupler is a diode on one side and can determine if its good because i'm getting a good reading both ways because something else must be interfering.

i was just learning about octos and realized some have a diode both way, when i looked at the data sheet i could not find the configuration picture but found another under google images that only showed one.

https://www.youtube.com/watch?v=kioSwtUZoAA

in this video showing using two multimeter to test each side but will need to wait till i get a second.

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

traced the leg from qs806 = lnw 31 all the way down to vs con on main board plug.

found a second lnw 31 at the bottom octo bunch and it reads the same as top so my finding was nothing.

off to test the optocouplers pcs8025 817b

ok im getting some weird reading on the diode side of the bunch of the optocouplers at the left of picture i posted.

the two on the end read good but all the ones in between read higher on one side and noting on the other and they appear to be all the same code.

they are each after the other the opposite direction so im testing the right sides.

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

found the short on the ymain, it was 2 smd 30n40p, its the 3 smd located center back.




don't got 2 100w light bulbs but might have them from now to Tuesday.

found a power supply local and gotta wait till next week for pickup.

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

been thinking about the optocouplers.

if you go to shop jimmy you can blow up the picture a find evey trace.

http://www.shopjimmy.com/samsung-bn4...pply-unit.htm#

if you include stb there is 5 different voltages and vs control witch equals 6 optocouplers.

i think the top one is for the vs control line on main board and there is one for voltage regulation on the set on the bottom with the rest

i see two lead's one from top and one from bottom going into the controller ic 2am a36f, it's at the top circuit ic 5081.

i have 3 diffrent 817b from a other power supply's but they got a different reading's. and one is dead.

will any 817b optocouplers do, also got 3 817c from a atx psu

seem like the 3 in the center where bad but all other voltages where stable.

either communication fault or bad optocouplers

gonna have to pull and test tomorrow.

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

i started testing the voltages on each side without vs activated and im getting 49 volts on the last emitter and collector and none on anode and cathode side.

from the data sheet it says 35 v collector and emitter and i getting no reading on the other side.

i think i might got something more wrong than just a opto.

first set of bottom pins are 1 volt, second 0, third 1.14, fourth 4.67, fifth 0

top pins first 37 v, second 29 v, third 34v, fourth 44v, fifth 49.

the top pins fluctuate from lower to higher and these are the highest i seen.

i'm seeing all high voltages on the top pins that are both anode , cathode and collector emitter.

this is me assuming that anode and cathode side are on the dot!

on top one number 6 i get nothing on anode and 33v on collector

im getting steady voltage reading on the low voltage= 15.3 ,5.29

i just tested va and get nothing , i may have shorted something wile testing!

i though va was active with lower but now i get nothing .


found this thread with some good info and troubleshooting methods with optos.

817c and a817b seem to match pretty well but these are the only data sheets i could find but they dont match my make.

http://www.datasheetspdf.com/PDF/DPC-817C/952198/1
http://pdf1.alldatasheet.com/datashe...T/EL-817B.html

http://www.videokarma.org/archive/in.../t-249524.html

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

when i activated the high voltage side i ended up getting 250 on the top pins of 1 and 2 witch are not both high voltage side because they are back and forth so i cut it there because its to dangerous.

something is shorted and leaking the 250 into those circuits trough the sense line,even the low voltage.

i don't know how things are not smoking, blowing my mind.

i would now only continue if i had a scematic so it's time to buy a new one.

sincerely,
bman4

[tom66]

Re: SAMSUNG PN51F5500AF 231v vs

I would look at the TL431 device. Should have 1.2V between REF and CATHODE when working. This is the feedback error amp.

Also, two 60W devices in series should be ok to test under light load.

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

i got the new power supply in but i'm still experiencing the same symptoms.

i got 207vs and 57.9 va now

ither bad x and y or bad main board at this point im stumpped.

[tom66]

Re: SAMSUNG PN51F5500AF 231v vs

Well, we don't know what got damaged by the high Vs.

Does the control board have a blinking light on it?

Do you see any glow at all from the panel, or flicker when the set is turned on?

Do you have an oscilloscope?

[bman4]

Re: SAMSUNG PN51F5500AF 231v vs

i really want oscilloscope !

https://www.badcaps.net/forum/showthread.php?t=31626

i want to think bad eprom but the Samsung chip next to second from top blue ribbon witch is a sps-h115 gets so hot it hurts in like a minute.

the light blinks every second then reboots, unplug x or y i get 5 sec.

panel flashes and stayed primed for a couple seconds the repeat

the primed panel has sparkles allover

no shorts on x or ymain.