Samsung 245BW power led comes on but no backlight

**triplefour** · 06-02-2014, 02:51 AM

Re: Samsung 245BW power led comes on but no backlight

i read in this thread https://www.badcaps.net/forum/showthread.php?t=15647 that the resistors are a common problem so i started checking mine...the one i said looked suspicious checked out fine. so did the 3 that are grouped together (rb805,806,807)
this one resistor though...RB801 which has the color code brown black yellow gold which should equal 10*10k ohms (would that be 100k ohms?) anyway it only tests at 420 ohms. and a weird thing (or maybe not) is that if i reverse the probes i get infinite resistance. why would reversing the probes have any effect on my resistance measurement?

**triplefour** · 06-02-2014, 02:53 AM

Re: Samsung 245BW power led comes on but no backlight

also is this an accurate test since the resistors are still in circuit? as i said i was able to get correct readings for the other resistors so it seems like testing in circuit is possible...at least in those cases...is there any reason why my in circuit test of this particular resistor might not be accurate?

**triplefour** · 06-02-2014, 03:47 AM

Re: Samsung 245BW power led comes on but no backlight

this is baffling: with the resistor i was just measuring at 420 this is when i have my multimeter in 2000 ohms scale. on 200 ohms scale it reads infinite (makes sense cause its over 200)
but if i put the scale up to 20k ohms i should expect to see less than 1...somethink like .4kohms, right? but it says 5.85 kohms
and it i put the scale up to 200k ohms i get 32k ohms
and if i put it up to 2000k ohms i get 221!

so which of these readings is correct? why am i getting wildly different numbers just by changing scale?

**triplefour** · 06-02-2014, 04:01 AM

Re: Samsung 245BW power led comes on but no backlight

also im having trouble understanding the resistor color code. for instance i have a resistor here that has 2 shades of green bands....a dark green and a light green. do i just call these both green or does the light/dark mean something too?

**triplefour** · 06-02-2014, 04:01 AM

Re: Samsung 245BW power led comes on but no backlight

and if theres no silver or gold band at one end, then how do you tell which way to read it?

**triplefour** · 06-02-2014, 04:54 AM

Re: Samsung 245BW power led comes on but no backlight

ok so i decided to remove the resistor to get a better reading on it.
now that i have out out of the board it reads infinate resistance no matter what setting im on.

the bands are brown black yellow so 10 x 10k should equal 100k ohms...

is it possible i could have ruined the resistor by too much heat from the soldering iron? whats my best bet at getting a replacement resistor? should i try to scavenge it from parts lying around or would it be a wild goose chase as there are so many different resistors? could i use one rated at any different resistance? like greater or less? or does it have to be exact? im thinking it has to be exact but i thought id ask since with capacitors u can get away with slightly different values...

Attached Files

**triplefour** · 06-02-2014, 05:44 AM

Re: Samsung 245BW power led comes on but no backlight

amazingly in my small collection of salvaged resistors i happen to have a 100k ohms resistor! but it is of a different type that doesnt have the color bands. also it says 2WJ on it...what does that mean? 2 watt joules???
also it says F054C ...is 54c like 54 degrees celsius? if so that doesnt seem very hot...
anyway im not entirely sure if i can just go ahead and replace this thing so im gonna wait here until someone actually reads all these posts!

Attached Files

**bammbammfran** · 06-02-2014, 05:46 AM

Re: Samsung 245BW power led comes on but no backlight

should be 100k
so 200k on your tester (when you check the resistor with your tester, do not touch the probes with your bare fingers or it may affect readings)

soldering heat should not have affected it

part number 100KZCT-ND at digikey.com

the pink no lines one should work, just check the resistance before installing it

**triplefour** · 06-02-2014, 07:12 AM

Re: Samsung 245BW power led comes on but no backlight

i couldnt wait so i went ahead and soldered it in. seems like its ok. but that didnt solve the problem... i notice i only have .88v going to the inverter board..... trying to read some of the other threads on this board but it gets a little too complicated for me. like they say to check the F9222L and they seem to say it has 23 pins and i can only count 20 pins on mine, a lot of which are just stubby pins not connected to anything...
please in very simple language explain what i should test next, and how i should test it

**triplefour** · 06-02-2014, 07:13 AM

Re: Samsung 245BW power led comes on but no backlight

on the F9222L btw i get 58v on most of the pins, but i get 28v on 2 of them

**triplefour** · 06-02-2014, 07:15 AM

Re: Samsung 245BW power led comes on but no backlight

and for cm802 i get 311v on the side closer to the mainboard and 155v on the side closer to the inverter board

**bammbammfran** · 06-02-2014, 08:09 AM

Re: Samsung 245BW power led comes on but no backlight

I could use a good picture of both sides of the board to help.

23 pin must have been a typo ?? 20 pin makes more sense but the voltage looks all wrong based on your numbers.
Check your tester batteries before going to far.
We have to check voltages in several other places
Fist spot would be for the 5 volts at the CN801 connector plug that goes to the main logic board.
It looks like those pins are marked for values on the board and so are the grounds

**triplefour** · 06-02-2014, 08:41 AM

Re: Samsung 245BW power led comes on but no backlight

thanks for the tips. ill have to do this tomorrow.

**C152Heavy** · 06-02-2014, 08:58 AM

Re: Samsung 245BW power led comes on but no backlight

Originally posted by triplefour

thanks for the tips. ill have to do this tomorrow.

Before digging deeper into this board suggest you put the original resistor back in and replace the caps even if they don't look bulged/burst, they're the most common failure point and a cheap and easy replacement.

I recently did caps on a 225BW, working fine now and the last thing I re-worked was a Linksys router, caps looked fine but were failed.

Good luck & let us know how you make out.

C152Heavy

**budm** · 06-02-2014, 08:59 AM

Re: Samsung 245BW power led comes on but no backlight

Did you already remove all the glues?
https://www.badcaps.net/forum/showthread.php?t=34692

**triplefour** · 06-02-2014, 09:20 PM

Re: Samsung 245BW power led comes on but no backlight

why would i put the original resistor back in when i can clearly test it with the DMM and see that it has infinite resistance! (open) i see your point on changing the caps cause theyre cheap but hey if i can test them first to be sure it would save a lot of soldering and a few bux. my goal is to identify the problem and only change what needs to be changed, not make guesses!

**triplefour** · 06-02-2014, 09:21 PM

Re: Samsung 245BW power led comes on but no backlight

i know theres no way my dmm without capacitance reading on it can tell me if a capacitor is good...but is there a way i can at least tell if one is definitely bad?

**triplefour** · 06-02-2014, 09:32 PM

Re: Samsung 245BW power led comes on but no backlight

heres the front and back pictures of the motherboard. and yes budm i removed all glues after taking this picture... still no dice. did the flashlight test too...nothing :/

im not getting the 24v out from the power board....

Attached Files

**triplefour** · 06-02-2014, 09:33 PM

Re: Samsung 245BW power led comes on but no backlight

i swear my phone should be able to take better pics than that...

Samsung 245BW power led comes on but no backlight

Samsung 245BW power led comes on but no backlight

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