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 11-29-2021, 05:31 PM   #1
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default TCL 75R615 has sound, no backlight

Have had this TV since June 2019, worked fine till today. Daughter was watching it and made a noise and went dark. I unplugged, left off then powered back on, no change. You can see the image with flashlight test, but has high pitched noise/whine and no backlight whatsoever......I also tried a factory reset with the reset button on the back. Any ideas where I should start troubleshooting? Im pretty good with soldering iron and multimeter, but I dont have any documentation on this TV so I dont know where to start.
thetonywarren is offline   Reply With Quote
Old 11-29-2021, 07:32 PM   #2
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: 2,330
Default Re: TCL 75R615 has sound, no backlight

I would start at power board. Sounds like shorted component causing the led driver to make noise. Need some pictures of boards.
__________________
I assume no responsibility for any stupid suggestions I might post.
dskall is online now   Reply With Quote
Old 12-05-2021, 05:14 PM   #3
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default Re: TCL 75R615 has sound, no backlight

So, I got some help yesterday to take the TV off the wall and got the back off to check out the boards....I did find a capacitor that was blown out,looks to be C312 a ceramic disc capacitor, very small and challenging to read, but was able to with a magnifying glass.....it seems to be a 220pf 1kv, I ordered some new ones from digi-key. A couple of questions, I dont notice with this type of capacitor that there is any polarity that needs to be observed? I have replaced numerous electrolytic caps and they have obvious polarity markings on the circuit board as well as the cap itself. Please see the attached pictures of the part number of the panel as well as some pictures of the internal boards, please offer up any help if you can....Thanks.
Attached Images
File Type: jpg PXL_20211204_161535900.jpg (639.2 KB, 6 views)
File Type: jpg PXL_20211204_161540255.jpg (658.9 KB, 5 views)
File Type: jpg PXL_20211204_161542271.jpg (713.1 KB, 4 views)
File Type: jpg PXL_20211204_161546018.jpg (646.5 KB, 5 views)
File Type: jpg PXL_20211204_161549464.jpg (786.2 KB, 4 views)
File Type: jpg PXL_20211204_161557041.jpg (617.4 KB, 4 views)
File Type: jpg PXL_20211204_161600510.jpg (697.9 KB, 14 views)
File Type: jpg PXL_20211204_171638591.jpg (483.6 KB, 13 views)
thetonywarren is offline   Reply With Quote
Old 12-05-2021, 05:32 PM   #4
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: 2,330
Default Re: TCL 75R615 has sound, no backlight

No polarity on those. Does it measure as shorted?
dskall is online now   Reply With Quote
Old 12-05-2021, 05:37 PM   #5
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default Re: TCL 75R615 has sound, no backlight

I just checked the component via continuity test and it is shorted.
thetonywarren is offline   Reply With Quote
Old 12-05-2021, 05:38 PM   #6
lotas
Badcaps Veteran
 
Join Date: Jan 2016
City & State: Sochi
My Country: russia
I'm a: Knowledge Seeker
Posts: 503
Default Re: TCL 75R615 has sound, no backlight

This is a high-voltage ceramic capacitor, they have no polarity, you can safely install it as you like.
lotas is offline   Reply With Quote
Old 12-05-2021, 05:41 PM   #7
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: 2,330
Default Re: TCL 75R615 has sound, no backlight

You can probably remove it and see if everything powers up. Just read my disclaimer first.
dskall is online now   Reply With Quote
Old 12-05-2021, 06:41 PM   #8
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default Re: TCL 75R615 has sound, no backlight

I think I'll wait till I receive the new component, before I power it back up....
thetonywarren is offline   Reply With Quote
Old 12-05-2021, 08:59 PM   #9
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,615
Default Re: TCL 75R615 has sound, no backlight

I would remove the disc cap and check it out of circuit, I would also check the mosfet QW301 & QW302. I usually replace these 1kv caps with a 2kv
R_J is offline   Reply With Quote
Old 12-05-2021, 09:18 PM   #10
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default Re: TCL 75R615 has sound, no backlight

When you say take the disc cap out of circuit, I'm assuming you mean the one that blew up and not another one near it or a different one? I did desolder it took it out of circuit and it tested shorted out ....I'll also check the two MOSFETs like you suggested......crap, I already bought the 1kv version instead of the 2kv like you said.....
thetonywarren is offline   Reply With Quote
Old 12-05-2021, 09:41 PM   #11
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: 2,330
Default Re: TCL 75R615 has sound, no backlight

I'm surprised you had video.
dskall is online now   Reply With Quote
Old 12-05-2021, 10:06 PM   #12
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,615
Default Re: TCL 75R615 has sound, no backlight

The 1k will be fine if that is what you ordered.
R_J is offline   Reply With Quote
Old 12-05-2021, 10:09 PM   #13
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,615
Default Re: TCL 75R615 has sound, no backlight

Quote:
Originally Posted by dskall View Post
I'm surprised you had video.
It seems to be the PFC circuit that has the shorted cap. The main board, t-con etc. likely operated and gave video but the led circuit needed the higher voltage and current to operate.
R_J is offline   Reply With Quote
Old 12-05-2021, 10:27 PM   #14
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: 2,330
Default Re: TCL 75R615 has sound, no backlight

Thanks again for the info. I get on here mostly to learn. Do you know what happened to budm? Looks to be about a year since he posted.
dskall is online now   Reply With Quote
Old 12-06-2021, 08:41 AM   #15
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default Re: TCL 75R615 has sound, no backlight

QW301 & QW302, as far as testing them....can they be tested in circuit, or do they need to be removed to be tested, I just want to make sure I do it the correct way.....im sure I can google a testing procedure, but I want to do it the quickest, most correct way....

Please let me know and thanks again for everyones help with this, it is much appreciated.....
thetonywarren is offline   Reply With Quote
Old 12-06-2021, 09:07 AM   #16
lotas
Badcaps Veteran
 
Join Date: Jan 2016
City & State: Sochi
My Country: russia
I'm a: Knowledge Seeker
Posts: 503
Default Re: TCL 75R615 has sound, no backlight

You can check without soldering them, their legs should not be short-circuited with each other, this capacitor is parallel to the diodes.
lotas is offline   Reply With Quote
Old 12-06-2021, 01:01 PM   #17
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default Re: TCL 75R615 has sound, no backlight

Ok, I'll test them later on this afternoon and post results on the mosfets....
thetonywarren is offline   Reply With Quote
Old 12-06-2021, 06:15 PM   #18
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default Re: TCL 75R615 has sound, no backlight

I tested both QW301 & QW302 in circuit and they are testing open across all legs.....I'm assuming per previous post that this means they are most likely good....
thetonywarren is offline   Reply With Quote
Old 12-06-2021, 07:21 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: 2,330
Default Re: TCL 75R615 has sound, no backlight

Well they shouldn't test open. Probably not testing them right, but they almost always test shorted if bad.
dskall is online now   Reply With Quote
Old 12-07-2021, 09:53 AM   #20
thetonywarren
Senior Member
 
thetonywarren's Avatar
 
Join Date: Feb 2013
City & State: Green Bay, Wi.
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Knowledge Seeker
Posts: 111
Default Re: TCL 75R615 has sound, no backlight

Ok, does anyone have a good source for how I should be testing these particular mosfets? Ive viewed a few videos on youtube, but just looking for suggestions.....

Thanks!
thetonywarren 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 09:00 PM.
Did you find this forum helpful?