Samsung LN46A550P3FXZA Squealing, clicking on and off

[Taterbug]

I am working on a 46" samsung that makes a loud squeal and has a weird raster when you turn it on. You can let is click on and off by its self for about two minutes then after it warms up it plays fine. I resoldered all the transistors on the heat sinks on the main board and replaced all of the electrolytic caps except the two large ones. They were none of the caps bulging. I unplugged the ribbon cables going to the t-con board and the buffer board and it still does the squealing. I suspect it is something on the main PS board but I need help at this point.
The PS board number is: BN44-00201A. I will attach a photo of the weird raster that has alot of lines with a green screen.

[Shinju]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

I have the 42" Samsung from this era doing exactly the same thing, you can try to reflow the MB but its a bad CPU solider job that needs to be either reballed or the board needs to be replaced.

Mine if I apply pressure and turn it on it comes right up no issues but if I let go and turn it on before its been warmed up it does what you are describing until it warms up enough to contact.

try heating up the MB with a hairdryer before you turn it on and see if it fires right up warm vs cold.

I just live with it as its an extra TV in the workout room and the mainboard at the time was 150+ minimum.

[Taterbug]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

Are you talking about the CPU on the video board???

[Shinju]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

mainboard

[Taterbug]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

ok, thanks I will give that a try.

[Taterbug]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

Heated the CPU and pressed on CPU while powering up and problem never went away. ????

[Shinju]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

It might be to the point that a reflow might fix it. Try pressing on the other larger chips and see if anything changes.


I don't think its a firmware issue but check and see if Samsung might have an update and if so update.

[Taterbug]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

What is strange after it heats up it plays like a champ. I pressed on all the chips and pressed on the boards and could not get it to fail. It's just at first when you turn it on after cooling down. I might see if I can find some cool spray and and shoot components one at a time and see if I can duplicate the problem. Thanks for the help. I will keep you posted.

[budm]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

You can use canned air duster upside down for cooling.

[Ltank]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

Squelling is normally caused by power supply or inverter boards being off the disigned frequency of operation.

[budm]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

The squealing coming from speakers, right? I have one 32" and one 46" that are doing the same right now, SJ has the repair kit for the main board but I cannot figure it out yet what the cause of the problem is yet.

[Taterbug]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

I have narrowed it down to the main board. Will have to check out the repair kit on SJ. I let it play until it warms up and problem goes away then I cooled off the main board until I was able to make problem keep repeating. I suspect a bad IC.

[sordids999]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

im not sure if this helps but i had a LG tv with high pitch squeal which was coming from the main board narrowed it down using a toilet roll holder to my ear which ended up being a ceramic capacitor that had a cracked solder joint re-soldered and all good

just a thought .....

[tibimakai]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

If I remember well, somebody found a bad capacitor on these A series boards.

[tibimakai]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

Shopjimmy has a picture with that capacitor:
http://www.shopjimmy.com/samsung-bn9...550p3fxza.htm#

[budm]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

Picture shows One cap and two ICs, but description shows 1 cap, 1 IC.
http://assets.shopjimmy.com/media/ca...side_2__12.jpg

[Taterbug]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

FIXED !!!! It was a bad solder joint on the cap on the back of the main board. C102 which is right above IC101.Below is the picture. Thanks everyone for your help it pointed me in the right direction.

[sordids999]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

glad its fixed although your attached image does not work to highlight the fault

[budm]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

I did a research on that cap, it is NEC-TOKIN NEOCAPACITOR 47uf 10V (NE AS7). The IC is MP2363DN: http://www.mouser.com/ProductDetail/...jHRp44hg%3D%3D
There are two buck regulator swithching circuit in that section.
I will try that on my board.
Better picture on post 16.
Notes on the output filter cap:
Output Capacitor
The output capacitor (C2) is required to
maintain the DC output voltage. Ceramic,
tantalum or low ESR electrolytic capacitors are
recommended. Low ESR capacitors are
preferred to keep the output voltage ripple low.
The output voltage ripple can be estimated by:

Where L is the inductor value and RESR is the
equivalent series resistance (ESR) value of the
output capacitor.
In the case of ceramic capacitors, the
impedance at the switching frequency is
dominated by the capacitance. The output
voltage ripple is mainly caused by the
capacitance.
In the case of tantalum or electrolytic capacitors,
the ESR dominates the impedance at the
switching frequency.

The characteristics of the output capacitor also
affect the stability of the regulation system. The
MP2363 can be optimized for a wide range of
capacitance and ESR values.

[tibimakai]

Re: Samsung LN46A550P3FXZA Squealing, clicking on and off

Boards like these I have myself too, but I don't have a TV to try it out.