Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting TVs and Video Sources
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 11-18-2021, 05:02 PM   #1
ajshoe
ajshoe
 
Join Date: Dec 2012
City & State: cincinnati, ohio 45215
My Country: usa
Line Voltage: 120VAC 60HZ
I'm a: Hobbyist Tech
Posts: 383
Default BN44-00274a dead

Have a Samsung PN50B550T2FXZA plasma set thats dead - no led lights, no TCON led lights, no standby voltage. Have re-soldered several bad spots on PSB board. looking at schematic - not getting 120 VAC at BD801S (HS802). followed circuit and don't see how 120 AC gets to this rectifier circuit. Replaced NT801S power thermistor SCK206. coil LE802 seems good. anyone have an insight into this ? checked all diodes and caps. thanks

Last edited by ajshoe; 11-18-2021 at 05:11 PM..
ajshoe is offline   Reply With Quote
Old 11-18-2021, 05:06 PM   #2
ajshoe
ajshoe
 
Join Date: Dec 2012
City & State: cincinnati, ohio 45215
My Country: usa
Line Voltage: 120VAC 60HZ
I'm a: Hobbyist Tech
Posts: 383
Default Re: BN44-00274a dead

pics attached
Attached Images
File Type: jpg 20211118_174923.jpg (669.9 KB, 10 views)
File Type: jpg 20211118_174913.jpg (818.5 KB, 10 views)
ajshoe is offline   Reply With Quote
Old 11-18-2021, 05:41 PM   #3
lotas
Badcaps Veteran
 
Join Date: Jan 2016
City & State: Sochi
My Country: russia
I'm a: Knowledge Seeker
Posts: 498
Default Re: BN44-00274a dead

AC voltage is supplied to the diode bridge through a relay.
Attached Images
File Type: png samsung_bn44-00274a.PNG (68.8 KB, 12 views)
Attached Files
File Type: pdf samsung_bn44-00274a.pdf (207.2 KB, 14 views)
lotas is offline   Reply With Quote
Old 11-18-2021, 06:12 PM   #4
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,604
Default Re: BN44-00274a dead

Have you checked FB801S? You will not have A/C at BD801S until RL802S is energized, and this will not happen until you have the standby circuit working. If the fuse is ok, check the solder connections on ICB801S

Last edited by R_J; 11-18-2021 at 06:20 PM..
R_J is offline   Reply With Quote
Old 11-18-2021, 06:13 PM   #5
dskall
Badcaps Veteran
 
dskall's Avatar
 
Join Date: Oct 2016
City & State: Bakersfield ca.
My Country: usa
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 2,316
Default Re: BN44-00274a dead

At what point are you losing voltage?
__________________
I assume no responsibility for any stupid suggestions I might post.
dskall is offline   Reply With Quote
Old 11-18-2021, 09:29 PM   #6
ajshoe
ajshoe
 
Join Date: Dec 2012
City & State: cincinnati, ohio 45215
My Country: usa
Line Voltage: 120VAC 60HZ
I'm a: Hobbyist Tech
Posts: 383
Default Re: BN44-00274a dead

will check ICB801S tomorrow. all 4 fuses are good. I see now - relay has to be enegerized to get 120 VAC across bridge. plug power in - absolutely dead. no +5 VDC standby, no clicks.
ajshoe is offline   Reply With Quote
Old 11-19-2021, 07:27 AM   #7
ajshoe
ajshoe
 
Join Date: Dec 2012
City & State: cincinnati, ohio 45215
My Country: usa
Line Voltage: 120VAC 60HZ
I'm a: Hobbyist Tech
Posts: 383
Default Re: BN44-00274a dead

Checked all solder connections. No 5 vdc on standby.
Attached Images
File Type: jpg 16373282720502678051851284261788.jpg (961.8 KB, 7 views)
File Type: jpg 16373283018413219043249207865742.jpg (1.05 MB, 4 views)
File Type: jpg 16373283159834943260088553143297.jpg (851.5 KB, 5 views)
ajshoe is offline   Reply With Quote
Old 11-19-2021, 10:11 AM   #8
dskall
Badcaps Veteran
 
dskall's Avatar
 
Join Date: Oct 2016
City & State: Bakersfield ca.
My Country: usa
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 2,316
Default Re: BN44-00274a dead

What is voltage on pin 4 CB8015?
Attached Files
File Type: pdf Infineon-ICE3BR2565JF-DS-v02_01-en.pdf (2.63 MB, 12 views)
dskall is offline   Reply With Quote
Old 11-19-2021, 01:41 PM   #9
ajshoe
ajshoe
 
Join Date: Dec 2012
City & State: cincinnati, ohio 45215
My Country: usa
Line Voltage: 120VAC 60HZ
I'm a: Hobbyist Tech
Posts: 383
Default Re: BN44-00274a dead

before I get voltage on CB8015 - is this done with all connections to PSB ?
can the PSB be tested for standby voltage on bench (nothing connected but 120 AC) ?
thanks
ajshoe is offline   Reply With Quote
Old 11-19-2021, 03:49 PM   #10
ajshoe
ajshoe
 
Join Date: Dec 2012
City & State: cincinnati, ohio 45215
My Country: usa
Line Voltage: 120VAC 60HZ
I'm a: Hobbyist Tech
Posts: 383
Default Re: BN44-00274a dead

dskall - you want voltage on pin 4 of HS802 (ICB801S) ? don't see a cb8015 anywhere on board or schematic
ajshoe is offline   Reply With Quote
Old 11-19-2021, 04:06 PM   #11
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,604
Default Re: BN44-00274a dead

Quote:
Originally Posted by ajshoe View Post
before I get voltage on CB8015 - is this done with all connections to PSB ?
can the PSB be tested for standby voltage on bench (nothing connected but 120 AC) ?
thanks
Yes it can be tested on the bench, You should get stby 5.2v like this.
To power on the rest of the supply, this power supply requires you install about a 1k resistor between stby 5.2v and PS_ON to turn on the other voltages.
Check the DC voltage ACROSS CB816

Last edited by R_J; 11-19-2021 at 04:08 PM..
R_J is offline   Reply With Quote
Old 11-19-2021, 05:35 PM   #12
ajshoe
ajshoe
 
Join Date: Dec 2012
City & State: cincinnati, ohio 45215
My Country: usa
Line Voltage: 120VAC 60HZ
I'm a: Hobbyist Tech
Posts: 383
Default Re: BN44-00274a dead

voltage across CB816 is 135 VDC.
voltage on pin 4 of ICB801S (HS802) is 0 VDC -when first plugged in goes to 0.35 VDC and then down to 0 VDC
saw bad solder on ICB801S (HS802) joints - touched them up. still 0 VDC on Standby and above checkpoints

Last edited by ajshoe; 11-19-2021 at 05:45 PM..
ajshoe is offline   Reply With Quote
Old 11-19-2021, 05:51 PM   #13
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,604
Default Re: BN44-00274a dead

That voltage is fine, it is the voltage that supplies icb801s and should also be on pins 1 & 2 of TB801s transformer. Keep the negative lead on CB816 (-) to check voltages in the primary circuit.
With a/c disconnected, check if RB807 is ok, it should read 0.4Ω (short) If it is open, the ic is defective.

Also, was NT801S bad? ie burnt? if it was then the RL801S relay contacts are bad and the relay should be replaced or at a minimum the contacts may be cleaned.

Last edited by R_J; 11-19-2021 at 05:59 PM..
R_J is offline   Reply With Quote
Old 11-19-2021, 06:25 PM   #14
ajshoe
ajshoe
 
Join Date: Dec 2012
City & State: cincinnati, ohio 45215
My Country: usa
Line Voltage: 120VAC 60HZ
I'm a: Hobbyist Tech
Posts: 383
Default Re: BN44-00274a dead

NT801S ohmed out at 20 ohms - it was not bad or burnt. I replaced it with new one anyway. don't believe relay or relay contacts are bad.
I'll check RB807 tomorrow. thinking the ICis bad - had 3 cold solder joints on it. The solder quality on this board is bad. found dozens of cold solder joints.
ajshoe is offline   Reply With Quote
Old 11-19-2021, 06:34 PM   #15
dskall
Badcaps Veteran
 
dskall's Avatar
 
Join Date: Oct 2016
City & State: Bakersfield ca.
My Country: usa
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 2,316
Default Re: BN44-00274a dead

Looks to be controller for standby transformer. Mounted on heat sink.
dskall is offline   Reply With Quote
Old 11-19-2021, 07:05 PM   #16
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,604
Default Re: BN44-00274a dead

Many times if the ic had poor solder connections, the ic becomes defective, sometimes they survive but not always. If RB807 is ok, the ic is likely still bad. I would also replace CB803 and CB815, they can dry out over time but still look and sometimes check ok. CX823 (standby output cap) could be weak as well on this age of a tv.

Last edited by R_J; 11-19-2021 at 07:10 PM..
R_J is offline   Reply With Quote
Old 11-19-2021, 07:49 PM   #17
dskall
Badcaps Veteran
 
dskall's Avatar
 
Join Date: Oct 2016
City & State: Bakersfield ca.
My Country: usa
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 2,316
Default Re: BN44-00274a dead

Since I am trying to learn here. What supplies start up voltage to looks like CB8015 or CB801s. To start controller it needs >15v if I read datasheet right.
dskall is offline   Reply With Quote
Old 11-19-2021, 08:00 PM   #18
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,604
Default Re: BN44-00274a dead

Quote:
Originally Posted by dskall View Post
Since I am trying to learn here. What supplies start up voltage to looks like CB8015 or CB801s. To start controller it needs >15v if I read datasheet right.

What schematic are you using? I don't see CB8015 or CB801s
In the datasheet you will see it has an internal startup cel that takes the voltage from the drain (pin1) and internally supplies startup vcc, and charges cb803 to about 18v. once it starts, DB802 keeps CB803 charged.

Last edited by R_J; 11-19-2021 at 08:10 PM..
R_J is offline   Reply With Quote
Old 11-19-2021, 08:28 PM   #19
dskall
Badcaps Veteran
 
dskall's Avatar
 
Join Date: Oct 2016
City & State: Bakersfield ca.
My Country: usa
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 2,316
Default Re: BN44-00274a dead

The above pdf from LOTAS and o/p picture of board. How is transformer getting voltage. Looks like it has to go through relay. Or does it get from NT801S?
dskall is offline   Reply With Quote
Old 11-19-2021, 08:46 PM   #20
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,604
Default Re: BN44-00274a dead

Quote:
Originally Posted by dskall View Post
The above pdf from LOTAS and o/p picture of board. How is transformer getting voltage. Looks like it has to go through relay. Or does it get from NT801S?
A/C is supplied from live, to one end of NT801s, the other end of the ntc connects to DB810~DB812, This Dc connects to FC803 (fuse) and charges CB816 to approx. 150vdc. This supplies the transformer Tb801s
Once the power supply is turned ON, RL801s shorts out the ntc to supply a bit more current for the standby circuit when it is operating at full capacity and supplying VCC & VCC_S to the other circuits in this supply.

Last edited by R_J; 11-19-2021 at 08:50 PM..
R_J is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2022
Powered by vBulletin ®
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 01:20 AM.
Did you find this forum helpful?