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 09-06-2021, 05:54 PM   #1
LugNut
Eager to Learn
 
Join Date: Oct 2017
City & State: Bowie, MD
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 6
Default PSLF201501B BN96-03057A Blown Capacitor

My TV uses the board BN96-03057A, model PSLF201501B.

The original issue was the standby light would go on then immediately turn off - TV would not turn on. Pulled the board to found 3 caps bulging so I replaced them.

After replacing the caps and confirming the fuse was good, I plugged the board into the wall. At that point the board was not generating power. Checked the fuse and it was blown.

I replaced the fuse a second time, plugged it in, and poof - cap NT811S made quite a pop! In hindsight, I had read somewhere that you can use a 40 watt bulb in place of the fuse. If it lights you have a short.

Here is my thought process for trouble shooting:

1. Pull the bridge rectifier to isolate the AC from DC
2. Test the bridge rectifier
3. Replace the popped cap. Not sure I can read a number off it
4. Apply AC power and check for 120v potential where the rectifier was
5. Check for a short on the DC side by injecting low power into the rail
6. If no sort found, install the rectifier and the light and give it a go.

Is my thought process close? I do not have the schematic, but I can kind of make out the paths.

Thank you.
Attached Images
File Type: png IMG_3525_2.png (1.36 MB, 15 views)
File Type: png IMG_3524.png (1.49 MB, 10 views)
LugNut is offline   Reply With Quote
Old 09-06-2021, 06:14 PM   #2
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,984
Default Re: BN96-03057A Blown Capacitor

one of the caps you changed was installed backwards or wasn't suitable .

Last edited by petehall347; 09-06-2021 at 06:17 PM..
petehall347 is offline   Reply With Quote
Old 09-06-2021, 06:20 PM   #3
LugNut
Eager to Learn
 
Join Date: Oct 2017
City & State: Bowie, MD
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 6
Default Re: BN96-03057A Blown Capacitor

Quote:
Originally Posted by petehall347 View Post
if you changed NT811S it was installed backwards or wasn't suitable .
Thank you, but I did not change NT811S. Pretty sure it is a nonpolarized cap.
LugNut is offline   Reply With Quote
Old 09-06-2021, 06:22 PM   #4
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,984
Default Re: BN96-03057A Blown Capacitor

i looked at pic after then edited my post .
petehall347 is offline   Reply With Quote
Old 09-06-2021, 06:47 PM   #5
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,350
Default Re: BN96-03057A Blown Capacitor

NT8115 is NOT a capacitor, it is a NTC thermistor 5Ω cold. Check that QP801s is not shorted, if it is, RP819 is also likely open. Check if FS802s fuse is ok, if it is ok then that eliminates most of the power supply circuit.

Last edited by R_J; 09-06-2021 at 07:03 PM..
R_J is offline   Reply With Quote
Old 09-06-2021, 08:41 PM   #6
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,350
Default Re: BN96-03057A Blown Capacitor

The thermistor is likely a 5D-13
R_J is offline   Reply With Quote
Old 09-07-2021, 01:23 AM   #7
Robinsosa
New Member
 
Join Date: Nov 2013
City & State: mombasa
My Country: kenya
I'm a: Knowledge Seeker
Posts: 14
Default Re: BN96-03057A Blown Capacitor

I hope this is the schematic diagram for the power supply.
Robinsosa is offline   Reply With Quote
Old 09-07-2021, 06:59 AM   #8
LugNut
Eager to Learn
 
Join Date: Oct 2017
City & State: Bowie, MD
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 6
Default Re: BN96-03057A Blown Capacitor

Quote:
Originally Posted by R_J View Post
NT8115 is NOT a capacitor, it is a NTC thermistor 5Ω cold. Check that QP801s is not shorted, if it is, RP819 is also likely open. Check if FS802s fuse is ok, if it is ok then that eliminates most of the power supply circuit.
Thanks RJ. FS802S is ok. I pulled QP801S out of the circuit and tested it with my component tester, which shows it is good. I did the multimeter test and it checked out good. I also pulled out RP819 - it is not open but has 0.3 ohms resistance. Is that good?

I looked at the datasheet for QP801S to learn more about it. I found some test circuits I am going to breadboard up to learn a little more before I stick it back in the board.

One thing I could not find information on is that the drain(2) is shorted to the back plane of the TO-247 package. Is that correct? Unless I missed it, it does not show in the datasheet. It was late when I checking it.

Thank you for helping me get this fixed.
LugNut is offline   Reply With Quote
Old 09-07-2021, 09:16 AM   #9
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,350
Default Re: PSLF201501B BN96-03057A Blown Capacitor

Yes the mosfet drain is connected to the tab, if the mosfet is not shorted drain to source it is likely ok. it sounds like the thermistor could be all that is wrong.

Last edited by R_J; 09-07-2021 at 09:23 AM..
R_J is offline   Reply With Quote
Old 09-07-2021, 12:42 PM   #10
LugNut
Eager to Learn
 
Join Date: Oct 2017
City & State: Bowie, MD
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 6
Default Re: PSLF201501B BN96-03057A Blown Capacitor

You were spot on with the 5D-13. Ordered a couple from mouser. Should be here in a couple of days.
LugNut is offline   Reply With Quote
Old 09-16-2021, 09:26 PM   #11
LugNut
Eager to Learn
 
Join Date: Oct 2017
City & State: Bowie, MD
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 6
Default Re: PSLF201501B BN96-03057A Blown Capacitor

UPDATE: Replaced the thermistor and fuse. There was 6V on the standby. Installed the board in the TV. When I turned it on, the MOSFET shorted and caused a bit of smoke and blew the fuse. I have replaced the MOSFET and fuse. Confirmed there is 6V on the standby. Installed the board back in the TV.

Now the standby light comes on but immediately goes off. Pushing the power button does nothing.

On the bench, the 6V is constant. I am concerned that it may be something in the main board now.

If I jump the ST_BY6.0V pin to the PWR-ON/OFF will that start the board and provide the 5.4VLINE and 24VLINE voltage to confirm they are working?
LugNut 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 - 2021
Powered by vBulletin ®
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 12:40 AM.
Did you find this forum helpful?