Toshiba 55g300u issue after issue

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What the tv does currently: no noise or picture just a black screen with a green power led. Sometimes when power is turned on you can hear a very faint electrical arc/buzz for a half second or so. It is hard to get it to repeat the noise on each power up.

I have a toshiba 55g300u. I replaced the power board and the jumpers on the backlight boards. When I got the TV it was broken. I opened it up and the jumpers from the master backlight board to the slave boards were burnt up on both sides. As in there are 2 sets of board. I replaced the power board and jumpers and when I did that the tv powered on but the jumpers I had put on I had just quickly soldered for the test. While running the test the TV powered on but I had a friend helping me (who isnt the most intelligent) and he kept trying to move the back light boards while the tv was on. He was trying to put them on the little knobs that hold them in place. During this some of the jumpers popped up and touched/shorted. Now I can't get it to work again. What could it be on the power board that blew? All the caps look good but I haven't tested them.

I haven't looked much at the logic board for issues.

Some where I have photos of the burned out jumpers I can upload. I will just need to find the photos.

The story/background of this TV: I received it for free from a friend not working. Opened it up and saw the burnt up jumpers and then got tired of it laying around and gave it to my boss. Now that he has it he is making me do all the labor while he buys the parts. To put it softly I am a little pissed off about this. At this point I just want the thing to work or be completely dead so I can get it out of my life :-)

Thanks,
Chris.

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Re: Toshiba 55g300u issue after issue

still havent found the problem

[budm]

Re: Toshiba 55g300u issue after issue

Any good clear pictures of the all the boards, the jumper that shorted to the chassis, the whole back side of the TV?

[CapLeaker]

Re: Toshiba 55g300u issue after issue

The story/background of this TV: I received it for free from a friend not working. Opened it up and saw the burnt up jumpers and then got tired of it laying around and gave it to my boss. Now that he has it he is making me do all the labor while he buys the parts. To put it softly I am a little pissed off about this. At this point I just want the thing to work or be completely dead so I can get it out of my life :-)

Thanks,
Chris.

Buy him a new one?, or put it in the trash can.

[x9x9x9x9x9]

Re: Toshiba 55g300u issue after issue

Here are 2 pictures 1 of each bacl light boards jumpers. I will take more photos in just a few minutes. I have reploaced the jumpers multiple times now but I soldered each one since I didn't have the proper molex connectors.

[budm]

Re: Toshiba 55g300u issue after issue

I hope they will be better pictures cause I am trying to see if the wire that touches the chassis is the B+ power wire or the transformer driver wire, right now I cannot tell form the pictures.
Did you check all the fuses on the inverter boards?

[CapLeaker]

Re: Toshiba 55g300u issue after issue

uff... its like I am wearing my grandmothers glasses. Check your pics... those are majorly out of focus.

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Re: Toshiba 55g300u issue after issue

Sorry, I quickly took those when I first opened it up to show my buddy the burnt up jumpers. I think the problem is the transformer I removed (I have a replacement board) Oh and this is not my solder job I was teaching a coworker.

[budm]

Re: Toshiba 55g300u issue after issue

Can we see the whole back side of the TV to see how all the boards are connected together?
There are more than one version of your TV:
http://www.shopjimmy.com/catalogsear...oshiba+55g300u

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Re: Toshiba 55g300u issue after issue

Here are the others

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Re: Toshiba 55g300u issue after issue

Oh sorry I just saw the reply wanting to see the back. Here you go. Thanks everyone. The transformer has had the kapton tape removed.

[budm]

Re: Toshiba 55g300u issue after issue

So the fuses on the inverter boards are OK?

[x9x9x9x9x9]

Re: Toshiba 55g300u issue after issue

So the fuses on the inverter boards are OK?

I believe so. What is the best way to test them? I just used a continuity test.

[budm]

Re: Toshiba 55g300u issue after issue

If the fuses are good, showing <1 Ohms, then check and see if you do have 24VDC feeding the fuses.

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Re: Toshiba 55g300u issue after issue

Okay. Tomorrow I will bring the second board up here and check that. I was measuring one of the 12v lines to the back light (i think) and it was come up to 8 volts or so then quickly drop out when the power button was pressed like the board said abort to the power operation. The electrical arc sound was coming from the transformer on the power board. I really hope thats not a normal thing because getting that off took a lot of work.

[budm]

Re: Toshiba 55g300u issue after issue

BTW, so right now the TV is totally dead, no green power LED?

[budm]

Re: Toshiba 55g300u issue after issue

Okay. Tomorrow I will bring the second board up here and check that. I was measuring one of the 12v lines to the back light (i think) and it was come up to 8 volts or so then quickly drop out when the power button was pressed like the board said abort to the power operation. The electrical arc sound was coming from the transformer on the power board. I really hope thats not a normal thing because getting that off took a lot of work.

12V is not used by the inverter board: look at P803, 804
http://assets.shopjimmy.com/media/ca...8932-top_1.jpg

You can disconnect the P803, 804 and see if the TV will power up.

[CapLeaker]

Re: Toshiba 55g300u issue after issue

BTW, so right now the TV is totally dead, no green power LED?

Yeah, I am wondering about that too. We need to know if there is standby voltage, maybe the TV powers up and there is no back light, or the whole thing is dead. So a detailed description on the power status would be good.

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Re: Toshiba 55g300u issue after issue

I am getting the green power led. When I hit the power button it goes out. Then I can hit it again a few seconds later and it will come back. Its like the back light circuit is dead but there is no sound either.

[budm]

Re: Toshiba 55g300u issue after issue

OK, the inverter circuit in this TV does not generate any error signal back to the main board what is going on with the inverter board, so the TV should work without having the inverter boards connected.
So lets find out the PFC Voltage booster circuit is working or not first, you will have to measure the DCV between the two legs of the main filter 450VDC caps (at any one of the two caps will be find).
The DCV on the cap should jump from 160VDC to >360VDC when power switch is activated and should stay at that level until the TV is turned off.
You will be working in the Deadly primary side of the circuit, so do not touch anything and do not let the probes slipped on you.