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Aric
Aric, Technician
Category: TV
Satisfied Customers: 37504
Experience:  15+ years in the field. Owner of AV Installation, OEM and Repair company
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I have a Sanyo 46" TV that when you turn it on, the power light

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I have a Sanyo 46" TV that when you turn it on, the power light comes on and then turns off after about 5 seconds. I was sure it must have been the power supply board and I replaced it. It still does the same thing. What elase could be the problem?
Submitted: 2 years ago.
Category: TV
Expert:  Aric replied 2 years ago.
Hello, My name is XXXXX XXXXX I will be glad to assist you. Please keep in mind that there may be a few minutes between replies, as I research your problem.
How long have you had the set for and when did the problem occur?


There are alot of things that could cause this problem, and to isolate it further you'd need to be able to measure voltages inside the TV to determine if either the T-Con, or Backlights are shorted shutting the TV down. What is your level of electronics experience?
Customer: replied 2 years ago.

I have a little knowledge on radios and TV's but I am color blind and I am limited at this point..


 

Expert:  Aric replied 2 years ago.

Unfortunately, there are three components that can cause the problems you're having.

I will try to explain this the best that I can here.


There are several things which could cause your problem. One is the Mainboard, the other is the T-Con (LCD Timing controller), or the Backlight Inverters.

 

 

As a quick test to see which board is causing the problem, disconnect the Backlight Inverters from the supply and see if the TV will power up without them connected. If so, you've found the source of your short, and would replace the backlight Inverter.

If the symptoms are the same with the Inverters disconnected, then you'd want to disconnect the two ribbon cables connecting the mainboard to the T-Con board- which is the small 5" x 7" board mounted at the center of the LCD panel. If the set powers up and stays on with the T Con disconnected, then you'd replace the T-Con.

If the set acts exactly the same whether or not the T Con or Inverters are disconnected or connected, then your mainboard is suspect, and the only board that you can't really test. The Mainboard works in tandem with the power supply to produce the rated voltages responsible for the TV turning on/off.


The link below is where you can visually identify, as well as purchase replacement boards for your TV:

http://www.shopjimmy.com/catalogsearch/result/?q=DP46848

 

 

If you need further assistance, simply reply back and I will be online later to assist you further (I have to step out and pick up my daughter right now).

 

If you're satisfied with my service, please kindly rate the answer accordingly.

 

 

Customer: replied 2 years ago.

Okay, I have a doctors appointment at 2 P.M. so I will get back to you after that.


 


Thanks

Expert:  Aric replied 2 years ago.
Okay that sounds good, thank you.
Customer: replied 2 years ago.

Sorry, I am back, Got back late and I guess you were gone. Are you here now?


 

Expert:  Aric replied 2 years ago.
I'm on and off everyday, and was on late last night too. I didn't see a reply, but you can post follow ups and I will reply back as soon as I see them- just like E-mail. Where are you at as far as troubleshooting?
Customer: replied 2 years ago.

Okay I have narrowed it down to what I think it must be the main board I think. I have removed the mainboard and the power light will not come on.


Is this right?.


 

Expert:  Aric replied 2 years ago.
You won't ever have a power light without the mainboard connected. The mainboard is the last possibility after we try the other tests described in my post. What we're more concerned with, is what were the results of disconnecting the inverters and the t-con board?
Customer: replied 2 years ago.

I will have to put it back in and go from there. I will be back later.

Expert:  Aric replied 2 years ago.
Okay, let me try and summarize the tests.

What we know as a fact, is that with all of the boards connected, the TV will turn on, then shut itself off a couple of seconds later- correct?

If we disconnect the Inverters, will the TV stay on? If so, then the inverters need to be replaced.


With the T-Con disconnected, will the TV stay on? If so, then the T-Con is causing the problem and needs to be replaced.


If neither- disconnecting the Inverters, OR disconnecting the T-Con will allow the set to stay on, then you'll want to replace your mainboard.
Customer: replied 2 years ago.

Okay, I hooked up the mainboard with it connected only to the power supply and it will not come on at all. Not even the power light. What now?

Expert:  Aric replied 2 years ago.
Can you proceed with the steps above exactly as described? Start with everything connected then proceed from there.
Customer: replied 2 years ago.

I hooked it all back up and did what you said. I disconnected the T Com and the power light came on and went off like before. I connected the T Com back up and tried it again and the power light would not come on at all. I disconnected the inverters and the power light would not come on.. Does the T-Com have to time out before it will be able to power up again?

Expert:  Aric replied 2 years ago.
Thank you for the reply. No, there isn't a time out condition presented by the T-Con in any way.

I would leave the set unplugged for several minutes, then try to power it up with everything connected except for the Inverters and see what happens.
Customer: replied 2 years ago.

The power light will not come on at all now regardless of which one is connected or disconnected.

Expert:  Aric replied 2 years ago.
Any click sound when the power cord is plugged into the wall, or power is pressed?

Any hum, or buzz coming from the power supply board?
Customer: replied 2 years ago.

No


 

Expert:  Aric replied 2 years ago.
Are you 100% certain all connectors, and cables are securely connected?

Is the Mains fuse on the power supply board open?
Customer: replied 2 years ago.

Yes everything looks okay but while checking I noticed the power button on the side of the cabinet is pushed in passed the cabinet hole. I can push it and I can hear it click.but it doesn't feel right. Do you have to take off the whole back to get to it to check it?

Expert:  Aric replied 2 years ago.
Yes you do. You shouldn't have the back of the tv in at this point though.
Customer: replied 2 years ago.

I had it off but I put it all back together. I just had it where I could just hook and unhook the cable connecters. Well back to tearing it apart.

Expert:  Aric replied 2 years ago.
Let's leave the back off so that we can perform the rest of the testing. Make sure that power button is not pushed in.
Customer: replied 2 years ago.

I have now check the power button and it is okay. Hooked it all up and no power. Disconnected the T Com and the power light will come on and then go off. Connected the T Com and disconnected Inverter and no power. I then connected both up again and the power light comes on and then goes off. Makes no sense to me.

Expert:  Aric replied 2 years ago.
Okay this is making sense. With the T-Con disconnected you have the same symptoms as you originally had, yet when you disconnect the inverters you have nothing. It's likely that the power supply needs to sense a load at the inverters in order to turn on. So, where we're at is either the mainboard or the Inverters. Seeing as the Mainboard being bad would not allow the TV to power up at all, we would want to replace the Inverters.
Customer: replied 2 years ago.

But with the inverter disconnected, shouldn't the power light stay on?

Expert:  Aric replied 2 years ago.
Not necessarily because it's likely that the supply needs a load terminated at this line to even turn on.
Customer: replied 2 years ago.

I have the inverters out. Is `there any way to check them other than visibly?

Expert:  Aric replied 2 years ago.
No I'm afraid there isn't.
Customer: replied 2 years ago.

I will order the inverters and will get back to you then.

Expert:  Aric replied 2 years ago.
Okay that sounds good. If you order them from shopjimmy they have a return guarantee in case we run into other problems.
Customer: replied 2 years ago.

They were out of stock. I will find them.

Expert:  Aric replied 2 years ago.
Okay sounds good.
Customer: replied 2 years ago.

Aric, Are you there?


 

Expert:  Aric replied 2 years ago.

I'm not on my PC but an on and off of the phone. Simply reply back as you would with email.

Customer: replied 2 years ago.

This is where I am at. I replaced the inverters and hooked it up and the power light would come on and then shut down just like before. I also got another main board and installed it and the power light would come on and stay on and the screen would flicker and that would be it. I tried scanning through the input menu with nothing happening.


 

Customer: replied 2 years ago.

Now I took out the new inverters and replaced them with my old ones and still no picture. I am getting sound though.

Customer: replied 2 years ago.

Are u There?


 

Expert:  Aric replied 2 years ago.

No I'm sorry I'm not online. Can you tell me if you press the menu if the menu will show on the display?

Customer: replied 2 years ago.

I'm standing by waiting on you. Let me know when you are ready.

Customer: replied 2 years ago.

No.....Nothing on screen. It will come on for a split second. I have an
idea that I got some bad inverters. I have ordered another set. Could it be
anything else?

Expert:  Aric replied 2 years ago.
I would check all connections at the mainboard and t con board at this point to make sure they're all seated properly. Right now its looking like the inverters are okay if you had the same symptoms with both the old and new inverters. I would also suggest checking the plug from the power supply to the inverters with a meter to ensure you have 24 volts somewhere on that plug. Let me know what you find.
Customer: replied 2 years ago.

I have put in another power supply board and it does the same thing. It will come on with sound and the screen will flicker a split second with the sound staying on.

Expert:  Aric replied 2 years ago.
I know you replaced the power supply once are you saying you replaced it again? Also, with the screen black and sound staying on, shine a flashlight directly against the screen and look very closely for a shadowy or dimly lit image barely visible behind the screen.
Customer: replied 2 years ago.

I can't see anything with the flash light. The inverters that I bought were used so that is why I think they may be bad. Also do the plugs connect directly to the power board?

Expert:  Aric replied 2 years ago.
I need to know right now if the screen itself is actually backlighting. In a darkened room does the screen glow slightly brighter than when the set is turned off?
Customer: replied 2 years ago.

It is just as dark on as it is off.

Expert:  Aric replied 2 years ago.
Unfortunately it sounds like you have a failed LCD panel, because there's not much else that would cause this. If the backlight inverters were not working, you'd be able to shine a flashlight and see a dimly lit shadowy image barely visible behind the screen. If the backlights were working then you'd have at least some lighting to the panel. Unless we have a faulty T-Con AND faulty inverters, then your panel has failed. You've already replaced the Mainboard and the Power Supply, then tried another set of Inverters and are still having the same problem with no video on the screen, and no backlighting. You have a bad LCD panel in this set I'm afraid, and this is the only component that is not replaceable cost effectively in your TV. I'm sorry for the bad news, but there's no other way to test the panel other than what we've already tried.
Customer: replied 2 years ago.

Even though it briefly comes on and goes off, it is bad.

Expert:  Aric replied 2 years ago.
Yes it's not uncommon for it to light for a second then go out, it simply means that the CFFL's inside the panel are out of spec. They're not reliably able to stay lit, and they are also not replaceable without replacing the LCD panel. Again, you've already replaced the power supply, mainboard and inverters, and these are all that are needed for the lighting in the LCD panel to work provided the panel itself is not bad. You're getting a couple flashes of light then a black screen, so this is telling us that your panel has failed. I wish I had other news on the set.
Customer: replied 2 years ago.

I still have inverters that I had already bought and they will be in Tuesday. I would like to try those before I give up. One other thing that bothers me is that the main board and the LCD panel going out at the same time. All the parts that I have used are used parts and it is possible that one of those may be bad.

Expert:  Aric replied 2 years ago.
Let me know what happens with the new Inverters. All things considered equal, right now it's looking like a faulty LCD panel, or one of the used boards is faulty. Let me know what results you get with the Inverters in the TV on Tuesday and let's see if this opens up any other ideas on this.
Customer: replied 2 years ago.

Is there a fuse on the T-CON board that may be blown?

Expert:  Aric replied 2 years ago.
I don't have a schematic of that particular T-Con so I can't say for sure, but it's possible. The fuse would be a small soldered in Pico fuse, or mini ceramic fuse.
Customer: replied 2 years ago.

Do the ribbons disconnect from the t-con or are they mounted on to it?

Expert:  Aric replied 2 years ago.

They disconnect from the T-Con. There is a flap at the bottom of the connector that lifts up to free the ribbon cable up to remove it. There's a Youtube video below that shows how this is done:

 

https://www.youtube.com/watch?v=Sx03jEaQsS8

 

 

Customer: replied 2 years ago.

I can't seem to find the tab. Is other ways they connect?

Customer: replied 2 years ago.

Is there something different on the Sanyo for disconnecting this as I watched this clip and I can't find the tab to click up.

Customer: replied 2 years ago.

I am stuck here. I have four ribbons that I cannot get off. These are a little different than the ones in the clip I watched. If I could get these ribbons off, I would just go ahead and get another t-con.

Customer: replied 2 years ago.

Here are some pictures if this will help.

Customer: replied 2 years ago.

are u there?

Customer: replied 2 years ago.

Never min d on all the last post....I got it out. It flipped down instead down.

Expert:  Aric replied 2 years ago.
I just got back in and havnt had a chance to view the posts yet. Will postback soon.
Customer: replied 2 years ago.

OK I found a 3 AMP fuse on the board and it checked good.

Expert:  Aric replied 2 years ago.
Alright, did you check this fuse using a multi-meter?
Customer: replied 2 years ago.

Yes.....It was good.

Expert:  Aric replied 2 years ago.
Okay. I'm not sure where else to go here aside from trying the other inverters out.
Customer: replied 2 years ago.

Ok...will check them out Tues.


 

Expert:  Aric replied 2 years ago.
Sounds good thank you.
Customer: replied 2 years ago.

Aric, The inverters that were suppose to be in today never arrived. I said I would try my old inverters and swapped them out. Bingo....I had sound and a picture. I don't understand why but I had the original inverters in first and it wouldn't work. Everything is okay now. I almost scrapped it out. I even bought another Sanyo TV online and it's suppose to be in this Friday.

Expert:  Aric replied 2 years ago.
Excellent and I am glad to hear its working. Bizarre that they didn't work before and perhaps it was a connection issue in one of the cables.
Aric, Technician
Category: TV
Satisfied Customers: 37504
Experience: 15+ years in the field. Owner of AV Installation, OEM and Repair company
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