Samsung 245bw No Power No LED

[Ober]

Re: Samsung 245bw No Power No LED

What settings on multi to test the 450 cap?
DCV 1000?

Board has been unplugged and off for several days, i did plug it in and try power last night before takin it apart (minimum 15 hours ago)

[selldoor]

Re: Samsung 245bw No Power No LED

Yes 1000vDC sorry doesnt have 600vdc.


Gone to bed!

[Ober]

Re: Samsung 245bw No Power No LED

OK now im stumped.... so i put to 1000 DCV and threw the black on negative and red on positive of the 450v and it stayed at 0000 and occasionally threw the negative sign before it... (tho ribbon cables havent been reconnected, i wasnt sure about the need with the power off, thought i was just checkin voltage left in the cap..)

now going to put the ribbons back on and test the cap...

how should i handle the board once i plug it in? just dont touch anything? so i guess the 450v wont harm the meter when plugged in and power switch on?

Thanks....

Edit: do i need to have the actual screen connected to the rest? the line of multiple ribbons? it seems it would be EXTREEMLY hard to get everything plugged in without havin that metal backing in the way... unless i was suppose to remove everything from the metal backing too... but i only removed the power cuase it seemed power was the issue... i have everything but that row of ribbons plugged in... is this how i should be testing or do i have to go the full mile and get that part plugged in and the board still accessable too.. -- If this is the correct way, then again i got 0000 result.. (also i assume im touching the leads to the solder/wire on the back of the board as the cap is so close to the board the leads arent even accessable between cap and board

[Lumberjack777]

Re: Samsung 245bw No Power No LED

Ok Ober. Unless you understand how to use that sophisticated multimeter. You could make matters worse or even burn it out. You said you had 2 capacitors that were not flat. I'd start there. 80% of the monitors I fix are simply bulging capacitors. Get the uF and voltage from them and order them from somewhere like digikey. Get the height, diameter, and lead spacing. You need to order good 105C capacitors like panasonic, nichicon, or rubycon. While they are on order, get a junk PCB board with capacitors on it and practice taking them out and putting them back in. That link retiredcaps gave you on soldering is the best soldering lesson I have ever seen online.

[selldoor]

Re: Samsung 245bw No Power No LED

@L777 he says he has NO power at all - dont think bad cap would cause that unless the Big One
@Ober
Ok try something else instead- no power required
On the power supply where the mains connector goes in
find the N in a circle. Just below that is a black arrow with DIP above it That arrow is pointing to a black rectangular component ( Bridge rectifier) numbered on the board perhaps BD601S it has 4 legs.
Find it on the other side of the board.
1, Meter on ohms 2000 black probe on the negative pin of the mains socket red probe on one of the two middle pins on the
Bridge Rectifier.
2 Do the same again but red probe on the other of the two middle pins.
3 Do the same again but black probe on the positive pin of the mains socket
So you should now have 4 readings.

Next, look at the bridge rectifier on the back of the board and write down 1 2 3 4 to represent the 4 solder pins. Meter on ohms 200
test red on 1 and black on 2 write down result.
test red on 1 and black on 2 write down result.
test red on 3 and black on 4 write down result.
test red on 4 and black on 3 write down result.
test red on 2 and black on 3 write down result.
test red on 3 and black on 2 write down result.
Post results

Next meter still on 200 ohms black probe on Bridge rectifier 1 and red probe on
positive leg of the big cap - write down result. then black probe on pin 4
red probe on negative pin of big cap - write down result.


When you have done those just using only the power supply plug it in and with meter on DCV1000 on the back of the board test across the pins of the big cap. Red on positive black on negative.
You should try and do this quickly and unplug it as soon as possible
after doing the test.

[momaka]

Re: Samsung 245bw No Power No LED

@L777 he says he has NO power at all - dont think bad cap would cause that unless the Big One

Even so, I would agree with Lumberjack777. If Ober is a newbie with electronics, he/she really would be better off not doing any sort of measurements on the hot side of the power supply.

@Ober: since you can't provide pictures, can you give us all of the information that's printed on all of the caps? - i.e. brand, series, voltage, capacitance (uF), diameter (in mm), height (optional... also in mm). If you're not sure how to get the brand and series, just get everything that is written on each cap and post it here.
Here's an example of how to post it:
brand ----- series ----- voltage ----- capacitance ----- diameter
CapXon --- KF -------- 25V --------- 470 uF --------- 10 mm
SamXon --- GF ------- 25V --------- 1000 uF --------- 12.5 mm
... etc.

[selldoor]

Re: Samsung 245bw No Power No LED

Even so, I would agree with Lumberjack777. If Ober is a newbie with electronics, he/she really would be better off not doing any sort of measurements on the hot side of the power supply.

Surely you have a bit of an impasse there - if you dont do the tests you will never get better, how do you decide at what point someone can measure a big cap - when does a newbie with electronics become not a newbie?

When do you let child cross the road on their own?

[momaka]

Re: Samsung 245bw No Power No LED

if you dont do the tests you will never get better, how do you decide at what point someone can measure a big cap

When the OP understands how to use the multimeter well and can comfortably do voltage and resistance measurements on the cold side, only then he/she can move to the hot side. It takes just one slip on the hot side to do a lot of damage to the PSU (well, on the cold side too for that matter - but at least there will be less fireworks). Also, the likelyhood of damaging your multimeter or getting shocked is much less on the cold side.

Otherwise, I do agree that if you don't try the tests you won't learn.

[Ober]

Re: Samsung 245bw No Power No LED

Well my meter shows a reading when im checking the fuses, but so far i havent gotten it to show a reading doing ANYTHING ELSE (oh yea, it did show a reading on the 802,805,807's too)

i put it to 2000ohm black on neg, red on center 1, showed the 1 on meter still, tried red on center 2, still 1 on meter..

is there some way to test that the meter is even working correctly? not one setting showed any numbers with the probes on my hands (as in the video on how to use multimeter) so that makes me wonder whats goin on..

[selldoor]

Re: Samsung 245bw No Power No LED

Those are the start of the results I would expect
You are not filling me with confidence here.

Meter on ohms 2000 - you should have a 1(one) on the left
Now touch the probes together should go to 0.00 or as near as.

Now meter on VDC 20 find a battery and test it.
Test your car battery?

If they look good please start again with the test.

[Ober]

Re: Samsung 245bw No Power No LED

Meter on 2000ohm, all test black 1 red 2,red 3 and black 4 red 2,3 are comming up with the 1 on left

Meter on 200ohm... here i can explain it easier, EVERYTHING tested 1 on left

(tho the test of touchin the probes together worked, also double AA (possibly fairly dead one) gave 1.3v on 20DCV setting)

before i plug it in, id like to know if thats what im suppose to be expecting..

[rogfanther]

Re: Samsung 245bw No Power No LED

First, black probe in the hole named "COM".
Red probe in the hole named VDC

meter on 200ohm, touch one probe to the other. Does it show 0.00 ou near it ?

By the way, is the battery you put in the meter new ?

Ops, we posted almost at the same time.

If in the ohms scale it shows 0.00 when touching both probes together, the meter seems to be working..

[selldoor]

Re: Samsung 245bw No Power No LED

You do not need to explain results of test - just write it out longhand using
the same words as we use otherwise we have no idea what you have done.

Result of test 2 suggests your Bridge may be shot but try again using ohms 20000.

[Rtech]

Re: Samsung 245bw No Power No LED

He has got Diode test on the meter, that would be much easier to determine if the Bridge is flty or not,instaed of using resistance

[Ober]

Re: Samsung 245bw No Power No LED

i donno which one your refering to as "test 2" but.. couldnt find a single thing at 20ohms that showed a reading...

finally got frustrated and started testing random shit... at 20DCV i finally found a reading... across the big cap it hit as high as 0.35 at one point but as i held it there (was tryin to makesure i had good connection) it slowly went down 1 point at a time now its showin 0.1...

dont know if that helps atall... but when im not sure if im doing things correctly and NEVER get a reading its quite hard to feel like im doing anything right..

so does this mean my bridge rectifier is prob dead?

[Ober]

Re: Samsung 245bw No Power No LED

KK Doin diode readings now..

[Rtech]

Re: Samsung 245bw No Power No LED

Number the bridge contacts 1 to 4,then measure 1-3 then reverse the leads and do it again. then 2-4 and reverse the leads.Then 2-3 and reverse the leads, then 1-4 and then reverse the leads....8 measurements in all

[Ober]

Re: Samsung 245bw No Power No LED

SellDoors Request Tests.. Refering to 1 as negative and 4 as positive
Red 1, Black 2 = 561
Red 1, Black 3 = 599
Red 3, Black 4 = 599
Red 4, Black 3 = 1 on left
Red 2, Black 3 = 1 on left
Red 3, Black 2 = 1 on left

Rtech Tests
Red 1, Black 3 = 599
Black 3, Red 1 = 1Left
Red 2, Black 4 = 580
Black 4, Red 2 = 1Left
2,3 = 1Left Both Ways
Red 1, Black 4 = 470
Black 1, Red 4 = 1Left

[selldoor]

Re: Samsung 245bw No Power No LED

Right - bridge is ok I had one wrong but rtech got it covered.

[selldoor]

Re: Samsung 245bw No Power No LED

ok can we try to see if the mains socket and Bridge are connected ok.

Ohms 2000
Black on mains negative red on bridge pin 2 =

Black on mains negative red on bridge pin 3 =

Black on mains positive red on bridge pin 2 =

Black on mains positive red on bridge pin 3 =

Then check if Bridge and mains cap are connected

Black on Bridge pin 1 and red on Cap positive pin =

Black on Bridge pin 4 and red on cap negative pin
(Cap negative pin is on side with white stripe) =