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**selldoor** · 03-31-2012, 11:53 AM

Re: Samsung 2253BW No power after re-Capping

Hi - welcome to the forum.
Some members do not like pictures posted in line- they may even pass over the thread and go on to the next one.
Can you post a picture of the whole of the bottom of the board.
Please post pictures jpgs no bigger than 2mb 2000x2000 using Manage attachments which is found by clicking on Go advanced which is below Quick reply.

I do not think you have told us what is/was wrong with the set other than a buzz. Did the back lights come on at all - could you see anything on the screen using a torch or bright light.

What happened to C302 - Trace pulled off? - can I assume you have tested from pin to next component C217? for continuity

**DemonBG** · 03-31-2012, 12:26 PM

Re: Samsung 2253BW No power after re-Capping

hi Selldoor,
Thank you for your kind response and it would seem in my finite wisdom i have forgotten to tell you what is wrong with the set

Before the component burned out as the power button was pressed the LED would blink and that was it - No backlight and blank screen.

Now the problem is more or less the same but the blue LED is solid (no longer blinking) and the cycling humming noise is now constant - I have been unable to detect any images on the screen either but will have another go.

The Trace at C302 had been pulled off by the person that had the TV last (attempted to repair it i assume?) Either way, i have followed the trace and checked continuity (there are a few other damaged traces, all repaired and tested).

EDIT:: MY mistake - it would seem this may be a 2 seconds to black problem. (or at least, it is now...) just plugged the screen in again and there is an image there but unfortunately the backlight is not...

Warm regards,
Demon

Attached Files

**NormanSaxon86** · 03-31-2012, 01:52 PM

Re: Samsung 2253BW No power after re-Capping

Hi and welcome.

Power supply problems can be categorize into no power, low output power, power supply cut-off after sometime.

Given that the screen itself does not show up with brightness & colors. Is the fluorescent tube and backlight inverter working?

Easy check list
1. A blown or broken fuse will prevent all power from coming to your TV.
2. Try reheating all the solder.
3. Some would just re-cap the entire power board from spike power could
4. Damage all caps around the re-capping job.
5. The eeprom can become corrupted.

Are you sure the inverter is supplied with the right voltage and attemps to start? The caps in psu can be the problem.

Does the screen work or gone check it? The first thing is to turn tv on and tap the screen lightly with your finger.Put a cloth over finger to keep prints off tv screen.When you do this does it flash a white light?

First make sure to hit the menu button on the TV's remote while the screen is black, and if you have sound, and nothing is there then friend while the set is on turn a bright flashlight on and shine at angle into the set push the TV menu button if you can see a image then your back light is not working. You can also check the transformers they are close to were the wires plug into the panel, make sure all transformers read the same amount of resistance if not you have found a bad one. Now you will have to check to see if the power supply is sending 24v to the back light, if not the power supply is bad. Cost back lights around 150.00 and power supplies around 100.00.

Put a * what you Tv has

1. Blank screen
2. TV still powers up, blue led lights up, and relays click at turn on
3. Sound still works
4. Picture may come back for hours at a time but not reliably
5. Picture may appear for a split second when turning off.
6. There are any power surges.
7. The set is not over heating and the vents are clear.

Danger

The RTN node (seen on the silkscreen at the top left connector(and others) ) is basically the common grounding point and is connected to Earth ground, the shiny metal backing of the screen, and all the metal mounting pegs that the power supply is mounted to. The black or negative lead of your multimeter should be attached to this point. I just stuck the black probe into one of the mounting studs and let it hang there (out of the way) so I could probe using the other(red) lead of the multimeter with one hand.

Start off with the TV unplugged and turned off. Attach the negative or black lead of the multimeter to any mounting stud near the power supply board. Now plug in the TV and make sure nothing explodes. Now turn on the TV with the remote control and again make sure nothing explodes. Is the screen blank? If so, good. You'll be able to probe the test points on the power supply to determine which voltage is not being produced. Make sure to make a good contact between the testpoint and the multimeter probe. If the contact is poor, the voltage readout may look as though it is fluctuating between the spec'd voltage and some lower voltage. For example, if the spec'd voltage is 180v, not pressing hard enough to connect the probe and the testpoint may result in a readout that wanders between 180v and 50v.

Buzz Humming

This can be caused by a bad diode in the bridge, leaky capacitors in the osc or feedback sections, bad optocouplers, bad protection diodes (D2, D6)on the MOSFETS (or other out of spec timing or control cktry. In 90% of cases where I had buzzing or vibration after repair, I'd replace these and the problem would go away.

2. Loose parts or de-laminated cores, chokes or coils (see above)

3. Bad AC to DC filter caps on the input side - Hum or buzz may be a resonant freq of the 50/60hz you are running on, or superimposed on a good but 'fuzzy' DC Input voltage (typically 330-380vdc) Put a DVM on ACV and measure it. My bet is you have 10-20vac on the DC and those transistions are causing problems

4. Bad Hi AMP diodes and/or filter capacitors or a feedback capacitor on the output side. Use the DVM and check the outputs for superimposed ACV

**NormanSaxon86** · 03-31-2012, 01:55 PM

Re: Samsung 2253BW No power after re-Capping

Originally posted by DemonBG View Post

hi Selldoor,
Thank you for your kind response and it would seem in my finite wisdom i have forgotten to tell you what is wrong with the set

Before the component burned out as the power button was pressed the LED would blink and that was it - No backlight and blank screen.

Now the problem is more or less the same but the blue LED is solid (no longer blinking) and the cycling humming noise is now constant - I have been unable to detect any images on the screen either but will have another go.

The Trace at C302 had been pulled off by the person that had the TV last (attempted to repair it i assume?) Either way, i have followed the trace and checked continuity (there are a few other damaged traces, all repaired and tested).

EDIT:: MY mistake - it would seem this may be a 2 seconds to black problem. (or at least, it is now...) just plugged the screen in again and there is an image there but unfortunately the backlight is not...

Warm regards,
Demon

If everything works but the picture try checking the fluorescent tube and backlight inverter.

Kind Regards
Norman

**selldoor** · 03-31-2012, 02:09 PM

Re: Samsung 2253BW No power after re-Capping

OK seen your edit
If it is 2 sec to black the back lights usually flash on
- did yours do that or do they not light at all.
There is a guide for 2sec to black here: start at post19
https://www.badcaps.net/forum/showthread.php?t=10419

As you had a Buzz this is often associated to transformers so I would check the secondary windings on the two inverter transformers. They should be within 3% of each other. Please post your findings.

I know you said you had tested the caps and whilst your shows they have capacitance and are not shorted, from what I have read the only near sure test is with an ESR meter.
My point is that C107 (What size is it) appears to be an original and as it is on the primary side may be the startup cap. It is important that this is good. Also in that area there are 2 diodes and although it may be the picture the solder on the top end ( on your picture) looks very dull compared to other pins and perhaps it needs reflowed. The diode would test ok but may not be connected to the trace.
Not much else to suggest till you get a new 202

**NormanSaxon86** · 03-31-2012, 02:18 PM

Re: Samsung 2253BW No power after re-Capping

See if the hum buzz is coming from the fluorescent light.

Why Ballasts Buzz
Inside the ballast, current is being reduced by use of an electric coil around a metal core. This creates a magnetic field. Over time, this magnetic field can change the shape of the core material, creating an audible vibration as the alternating current we use for electricity flows through the wire.

Transformer
In the United States, a transformer is needed to increase the voltage reaching the light fixture. Transformers can develop a buzz as they age. Newer electronic ballast systems have smaller transformers that make a higher-frequency sound. Higher frequencies are more difficult to hear under ambient noise and would be less noticeable.

**NormanSaxon86** · 03-31-2012, 02:21 PM

Re: Samsung 2253BW No power after re-Capping

To fix a quiet humming noise emanating LCD Monitor it was useful for me to understand how an LCD Monitor works.

Adjust the brightness to a value greater or equal to 95. Mine was set at 50 by default and the humming noise was definitely audible at a brightness setting of 50. As I adjusted it towards 95 it gradually got fainter until it faded at 95.

**NormanSaxon86** · 03-31-2012, 02:36 PM

Re: Samsung 2253BW No power after re-Capping

2 seconds to black problem seems the signal that turns on and off the Backlights may be the problem

Usually that means you have a bad backlight. There are sort of two kinds of backlights in an LCD monitor. One kicks on really quickly but uses a lot of power, the second one turns on slowly but is better 'for the long haul' and the power hungry one turns off. It sounds like your 'second' backlight is dead.

If you get a really bright flashlight and shine it on the dark screen, I bet you can still see (faintly) your desktop and icons and stuff.

http://www.aplusperfect.com/articles...pacitor_repair

**selldoor** · 03-31-2012, 02:41 PM

Re: Samsung 2253BW No power after re-Capping

@NS86 - I hope you are not confusing the OP - your original information although perhaps
not incorrect relates on the whole to Televisions.
Your Second post is cut from an Ehow.com article that relates mainly to Fluorescent
Ceiling lamps in the US.
The OP is working on a Monitor in the UK.

**retiredcaps** · 03-31-2012, 02:43 PM

Re: Samsung 2253BW No power after re-Capping

Originally posted by DemonBG View Post

When testing the components i get the following readings (Using the Diode setting on the DMM):

Burned STM8309 (U202)
1 - 7/8: 0.49V
2 - 7/8: 0.93V
3 - 5/6: 0.16v
4 - 5/6: 0.16v

Non-Burned STM8309 (U203)

1 - 7/8: .366V
2 - 7/8: .846V
3 - 5/6: 0.023v
4 - 5/6: 0.717v

All of those readings are taken in-situ with Positive on pins 1 - 4 and negative on pins 5 - 8.

1) This is why some regulars don't like inline images

https://www.badcaps.net/forum/showpo...5&postcount=12

2) For the diode readings above, what are the readings in the other direction? That is, red on pins 5-8 and black on pins 1-4?

3) Also, test both mosfets for shorts following section "2) Shorted Transistors/MOSFETs"

https://www.badcaps.net/forum/showpo...4&postcount=19

**DemonBG** · 03-31-2012, 02:47 PM

Re: Samsung 2253BW No power after re-Capping

Hi All,

Thank you so much for the responses - i cannot believe how helpful this forum is!

The back light on the monitor does come on occasionally for a split second or two and i get a good, clear image. beyond that i need to shine a bright light onto the screen and i can see my desktop under it - So it would seem the panel itself works but the backlight system may be speculate.

I realised that regardless i would need to replace those two SMD's (202) which would have cost about 8 GBP so i opted to buy a new board altogether for 14! (Seemed wise). If that doesn't cure the problem it can only leave the bulbs...

The humming is not coming from the backlight but some component on the board itself (it is a feint "Digital" buzzing noise which changes frequency).

**NormanSaxon86** · 03-31-2012, 04:38 PM

Re: Samsung 2253BW No power after re-Capping

Originally posted by DemonBG View Post

Hi All,

Thank you so much for the responses - i cannot believe how helpful this forum is!

The back light on the monitor does come on occasionally for a split second or two and i get a good, clear image. beyond that i need to shine a bright light onto the screen and i can see my desktop under it - So it would seem the panel itself works but the backlight system may be speculate.

I realised that regardless i would need to replace those two SMD's (202) which would have cost about 8 GBP so i opted to buy a new board altogether for 14! (Seemed wise). If that doesn't cure the problem it can only leave the bulbs...

The humming is not coming from the backlight but some component on the board itself (it is a feint "Digital" buzzing noise which changes frequency).

Great to hear you do not have to replace the backlight DemonBG.

Very good thinking cost time effective wise. I hope to hear of your progress.

The humming board could be danger or just a ground loop problem. Might be a capacitor not getting enough power. Also look for the audio part of the board Check for ground it is a common problem. Some humming is common also and I would be worried if I did not hear it.

Debris from caps could be on the board suggest taking the whole board out but you can do the same if you know what can shock you. So wipe down the whole board with a dry lint free cloth.

Do you have the pictures of the surface-mount device SMD's (202) we might be able to tell you what iti is. Also use proper Potting the Thermo-setting plastics or silicone rubber gels are often get used. You will need tweezers also.

I would like to know if you tv has sound?
You can play sound from you pc on you tv if so you know you have sound.

**NormanSaxon86** · 03-31-2012, 04:57 PM

Re: Samsung 2253BW No power after re-Capping

Originally posted by selldoor View Post

@NS86 - I hope you are not confusing the OP - your original information although perhaps
not incorrect relates on the whole to Televisions.
Your Second post is cut from an Ehow.com article that relates mainly to Fluorescent
Ceiling lamps in the US.
The OP is working on a Monitor in the UK.

I think my troubleshooting was logical, The post is covering easy stuff to check. The Ehow is not only from lamps it relates to any florescent. I wanted to share Ballasts Buzz could be the issue. I found it at ehow like you did after I posted it....

I understand the OP problem just want to help and see the OP happy enjoying his new monitor

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