sylvania 32" lcd supply voltage to backlight board


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sylvania 32" lcd supply voltage to backlight board

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biotech1
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Oct 28, 2011, 12:34 AM

Post #1 of 24 (9125 views)
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sylvania 32" lcd supply voltage to backlight board	Can't Post

Im trying to diagnose an issue with a Sylvania 32" lCD tv model # LC320SL1. It was apparently hit by lightning while off so I suspected the diodes on the power supply. They are fine. The fuse on main/power board was blown. I replaced the fuse to find it only blows again. Trying to isolate I unplugged the backlight/inverter board. With this board unplugged from main board the fuse will not blow. I checked some voltages on the main/power board and found 160VDC going to the backlight/inverter board. Does anyone know if this is the correct voltage range? Thanks for any help. Assc in electronics but I used to only work on CRT TVS years ago so im a little lost and I have to keep stopping to look up data sheets on all devices I want to check on boards.

jts1957
Veteran

Oct 28, 2011, 1:06 AM

Post #2 of 24 (9119 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Usually 12 to 24 volts. Make sure you are referencing the correct ground point. Unimpressed

Ron:
SS8 & SS9 both available on elektrotanya.

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Location: Far, Far Away

(This post was edited by jts1957 on Oct 28, 2011, 1:10 AM)

Ron.M
Veteran

Oct 28, 2011, 1:06 AM

Post #3 of 24 (9118 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

biotech1;....

I do NOT work on LCD , LED or Plasma TVs...
BUT , I may have found a service manual for you...

This is for model number;... LC320SS8 which may be close enough...
Here is the link;=>...
http://servicetron.com/sylvania.html

Go down about 3/4 the way & you'll see " SYLVANIA LC320SS8 LCD TV SM "...
OR you can just click on the above underlined purple model number for instant download...

Hope this helps....

GOOD LUCK.... Sly

.....

jts1957;.....TIED ya !!!!! Both of us posted at 5:06 !!!!... Wink

...
But , you beat me by sec(s)....

Have a GREAT evening & weekend.... Sly

.....

Later...Ron.M.... Cool

....
Veteran & Retired TV technician

(This post was edited by Ron.M on Oct 28, 2011, 1:09 AM)

Ron.M
Veteran

Oct 28, 2011, 1:50 AM

Post #4 of 24 (9109 views)
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Re: [Ron.M] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

biotech1;....

I downloaded this manual....
2 things;...
1)...This is by far one of the best service manuals I've seen in a LONG while for LED/LCD TVs...
2)..Manual comes zipped....
I had a bit of a problem opening it up...
IF you can not open yours , there's a way to get my manual to you...
Just ask...
It has complete schematics , INCLUDING POWER SUPPLY...
Has full parts list & drawings...

Have a GREAT evening & week... Sly

....

Later...Ron.M... Cool

...
Veteran & Retired TV technician

jts1957
Veteran

Oct 28, 2011, 1:56 AM

Post #5 of 24 (9107 views)
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Re: [Ron.M] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

But neither manual may be close enough to HIS set. Wink

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Location: Far, Far Away

74f100
Enthusiast

Oct 28, 2011, 2:13 AM

Post #6 of 24 (9103 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

That set has a split power supply. What you are calling the inverter is called an Inverter power pcb by Funai. The other is the Jack power.

The problem,,, these are a Royal PITA to troubleshoot. Probably the easiest is simply shotgunning the transistors and diodes on both boards. If it blows the main fuse, there is a dead short fairly close to the input supply.

I'll do my best to look this set up tomorrow, and provide any specific data on it.

Jim
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Ron.M
Veteran

Oct 28, 2011, 3:32 AM

Post #7 of 24 (9096 views)
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Re: [74f100 & jts1957 ] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

jts1957;....

http://servicetron.com/sylvania.html & SYLVANIA LC320SS8 LCD TV SM are for the SAME manual...

Quote

But neither manual may be close enough to HIS set. Wink

TRUE , that's WHY I said;=>...

Quote

This is for model number;... LC320SS8 which may be close enough...

The invisible words are "to his set" !!!

74f100;.....

Is there that much difference between "LC320SL1" & "LC320SS8" ???
I'm thinking that the "SL1 & SS8" have to do with model specific features , functions etc...

Thanks for your help.....

Have a GREAT evening.... Sly

....

Later...Ron.M.... Cool

...
Veteran & Retired TV technician

jts1957
Veteran

Oct 28, 2011, 6:14 AM

Post #8 of 24 (9091 views)
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Re: [Ron.M] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Guess you missed my edit on Post #2. Wink

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Location: Far, Far Away

74f100
Enthusiast

Oct 28, 2011, 1:49 PM

Post #9 of 24 (9087 views)
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Re: [Ron.M] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Ron,,,,yes potentially a big difference. According to Funai, an LC320SS8 doesn't exist. Under the LC320 models, there are 3 different chassis'.
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74f100
Enthusiast

Oct 28, 2011, 1:57 PM

Post #10 of 24 (9086 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Ok, at work now, and looking at the manual.

That set usually has shorted diodes on the jack power supply, I've also had the main filter cap cause the fuse to blow.

When you dis connect the Inverter power supply, you are preventing the jack power from turning on. I also disconnect it when testing, but only to look for a short on the main supply line (what you read as 160v). Look for any short on the inverter supply.
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Ron.M
Veteran

Oct 28, 2011, 7:23 PM

Post #11 of 24 (9078 views)
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Re: [jts1957] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

jts1957;...

Re; Your edit.....

Quote

Guess you missed my edit on Post #2. Wink

MISSED it ???...Hell , I wasn't even aware that you made an edit !!!!
6 posts later you advise me of an edit notice..... Unsure

....
We do not get email notices for edited posts...
But , you already know that.... Wink

....

Quote

Ron:
SS8 & SS9 both available on elektrotanya.

When I was at "elektrotanya" , I was looking for "LC320SL1" , HIS model , NOT "LC320SS8 OR LC320SS9" which I was NOT aware even existed at that time....
I discovered "LC320SS8" at servicetron.com when I was looking for "LC320SL1" & thought it may be close to his set...
Which I now know is NOT....
Dats settled, right ???... Wink

...
Remember I do NOT work on these type sets & was just trying to help.... Wink

...

I'm going to the "bleachers" & watch this unfold..... Sly

....

Have a GREAT day & weekend.... Sly

....

Later...Ron.M... Cool

...
Veteran & Retired TV technician

(This post was edited by Ron.M on Oct 28, 2011, 7:27 PM)

74f100
Enthusiast

Oct 28, 2011, 8:56 PM

Post #12 of 24 (9071 views)
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Re: [Ron.M] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

You can't go to the bleachers Ron!!!!

I had a call today on the very same set today. I have all the parts, all the literature, and I still hate working on these sets. Even with everything, you still end up throwing parts at these many times. In the case of this set, this shouldn't be as hard as many of them are. We know it has a short in a primary part of the power supply.

Jim
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Ron.M
Veteran

Oct 28, 2011, 9:09 PM

Post #13 of 24 (9068 views)
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Re: [74f100] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

74f100;...

......................................................................................................

Have a GREAT day & weekend.... Sly

....

Later...Ron.M..... Cool

...
Veteran & Retired TV technician

biotech1
New User

Oct 28, 2011, 11:51 PM

Post #14 of 24 (9061 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Wow thanks guys for all the posts and the enthusiasm. I was very sure of the same thing that is it a dead short very early in the power supply. I have checked the diodes on the jack side supply board(the very large rectifier ones) and they are fine. Ron I couldnt get that manual to open when I downloaded it in zip format it said it was corrupted. I see an online store called shopjimmy has both boards very reasonable and I thought I would just replace them as compared to spending many hours of time trying to troubleshoot to component level. What someone called the filter cap are you referring to what I have always called the ripple smoothing cap? I dont have an lcr meter so checking the caps I would imagine you check for continuity and watch to see if you have initial continuity and then to none as the capacitor reaches full charge? or if it is shorted you would see a steady resistance? Thanks for all the help guys.

biotech1
New User

Oct 29, 2011, 12:47 AM

Post #15 of 24 (9057 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Oh I forgot to ask if any of you have ever bought any parts from shopjimmy? It seemed to be legit as far as I could tell and they are even iso certified. The parts all appear to be used and probably not tested but they come with 6 month warranty. But possibly bad boards throws a wrench into the shotgun method a bit.

biotech1
New User

Oct 29, 2011, 1:31 AM

Post #16 of 24 (9055 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

hey I might have this thing figured out. Found a shorted diode on the inverter board. Its the largest diode on the board just a half inch away from the "hot" area. it is a 31DF4 diode which I looked up and it is an ultrafast rectifier diode for up to 400V and max 3A. Only large diodes I have in my shop are standard silicon 6A2 diodes which are 6amp200V. I wonder if the diode needs to be fast recovery time and weather they put an overkill diode in and 200V would work. The new one I have is much larger physically so I would say it could handle more disapation of heat.

Ron.M
Veteran

Oct 30, 2011, 7:32 PM

Post #17 of 24 (9031 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

biotech1;...

Time for me to get outta de bleachers since it's been almost 2 full days & no one replied to your posts...
Some dangerous words in your posts...

1)...Do NOT sub THAT diode !!!
That IS a "ULTRA-FAST, 3A, 400V" diode & your "6A2 6amp 200V" diode WILL pop in a heartbeat....
May also cause further damage if the bad one didn't already...
And , YES , it NEEDS to be fast recovery...
2)...The size of the diode has NOTHING to do with heat dissipation....
They are NOT rated in watts...
3)...That diode can/should be able to be purchased for under a buck USD...
Not worth the risk of subbing...
4)...shopjimmy has been touted very highly by some techs here..
I have NO personal experience with shopjimmy....
Bad "good" boards can be bought anywhere...
That's why the reputable dealers have warrantys...

As for the manual;...
IF you downloaded the manual from the link I gave , it is NOT corrupted...
It has a quirk to open...
I can either explain how to open it OR send you my pdf...
If you post the reference number of the diode , I'll look it up in my manual & see what is there...
However;...
74f100 implied that my manual is not the right one...
So the manual I have may be useless here..

You have a choice to make here..
1)....Order the exact diode & replace it with a LOT of prayers...
2)...Order the board you think is bad & replace it with some prayers..
3)...Continue on with your troubleshooting till you possibly find ALL the bad parts , then order/replace them..

BTW:...
I check caps with a capactance checker & for lytics I also use an ESR meter....
Using a meter & checking continuity is for resistors....
Not a reliable way to check caps of any kind...
Only good IF the cap IS shorted...

"Ripple smoothing caps" as you call them are usually ONLY power supply filter caps with usually high capacty values...
"Filter caps" can be in just about any circuit including the power supply & have a wide range of values....

I think I covered everything.... Wink

...

There you have my 8 cents worth.... Wink

....

Have a GREAT day.... Sly

....

Later...Ron.M.... Cool

....
Veteran & Retired TV technician

(This post was edited by Ron.M on Oct 30, 2011, 7:41 PM)

biotech1
New User

Oct 31, 2011, 3:39 AM

Post #18 of 24 (9019 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Thanks for the updated reply. I have checked the filter caps they are all good. I had a good feeling I couldnt use the sub diodes. I found the right ones and have them on order. I have since also found a shorted MOSFET n-channel transistor on that same board. It is a k7a50d. I looked up spec sheet on it. I cannot find it anywhere online. Do any of you know a website with a cross reference on what transistors might work in its place. I found one that is very similar and very common and the same voltage and slightly higher amp rating it is an IRF840B. The reaction times are slower on this one than the original so it probably wont work either.

jts1957
Veteran

Oct 31, 2011, 6:57 PM

Post #19 of 24 (9006 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

http://www.semicon.toshiba.co.jp/...datasheet_100603.pdf

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Location: Far, Far Away

74f100
Enthusiast

Nov 1, 2011, 12:28 PM

Post #20 of 24 (8989 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Ok,,,, no notifications from this thread. Didn't mean to ignore anyone.

I'll look for that diode when I get to work, I may have a used one. I keep these boards when ever possible for just such an occasion.

Jim

BTW, as usual, Ron's info on everything else is spot on.
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74f100
Enthusiast

Nov 1, 2011, 6:26 PM

Post #21 of 24 (8986 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

I just checked, I don't have that diode or that pcb in parts.

Shopjimmy is a great supplier, we used them at least once per week. IIRC they have a 6 month warranty on all part they sell.

Last check on that diode,,,make sure to disconnect one side, then check it again for a short.

Good luck,
Jim
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biotech1
New User

Nov 2, 2011, 2:13 AM

Post #22 of 24 (8980 views)
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Re: [74f100] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

Thanks guys for all the help. I would love to have fixed this tv component level. Taking forever tracking down all the parts. I just conceded and ordered both boards from shopjimmy, hopefully that does the trick.

ALBERT213
New User

Nov 2, 2011, 9:02 AM

Post #23 of 24 (8972 views)
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Re: [biotech1] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

THANKS FOR THE POST..

_______________________-
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jts1957
Veteran

Nov 2, 2011, 11:55 AM

Post #24 of 24 (8970 views)
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Re: [ALBERT213] sylvania 32" lcd supply voltage to backlight board [In reply to]	Can't Post

You would think this guy is here to advertise (read Spam) judging by his lame first post and the non-clickable links in his signature. Crazy

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