Toshiba 37" inverter board failure

[whatusername]

Re: Toshiba 37" inverter board failure

he does not know he said he bought the tv in a lot but is 100% sure it worked cuz the tv only had a cracked screen and was on and had video when he pulled the boards and bagged them..

[whatusername]

Re: Toshiba 37" inverter board failure

so I take it there's no chance that the inverter board is pulling down the voltage?

[budm]

Re: Toshiba 37" inverter board failure

No, because your old power supply board is able to put out the 24V for the inverter to run and gives you the backlights. You should be able to put your old board back in and get the same condition as before, backlights on but no pictures shown on the screen due to no 12vlcd.

[whatusername]

Re: Toshiba 37" inverter board failure

true that makes sense.. when I get home from work tonight I'll put the old boy back in and make sure I still get back lights

[whatusername]

Re: Toshiba 37" inverter board failure

so bud i was testing the new broken board using the old one for reading comparison and came across this big thing on the top left i think it could be a bridge rectifier not sure but it failed a test againt my old one.. it shows open on one of the leggs its q660 u got info on it? str-z2589

ok its a power ic http://www.datasheetdir.com/STR-Z2589+SMPS-Controller

[budm]

Re: Toshiba 37" inverter board failure

You mean Q860,which is for the 12V and 24V power supply. That means there is problem with that section on your new board that it cannot supply the voltage to run the inverter board.
Also it is where that mod is done to it on your replacement board.

[whatusername]

Re: Toshiba 37" inverter board failure

yes from the test i have done between the boards on my old board there are a couple leggs that show a 1 in diode mode when i touch them and on this board those same legs show a value in diode mode so that would mean its faulty correct?

[whatusername]

Re: Toshiba 37" inverter board failure

because i am thinking of swapping str-z2589 from the old board to the new board.. and the resistor was added to a zenor diode mine original reads 793 in diode and where they put the resistor on that same zener it reads 693 so its 100 difference in the 2

[budm]

Re: Toshiba 37" inverter board failure

Yes, I think we already know that the new board has problem when it cannot power up the inverter board. I wonder what that MOD with that resistor is about.
You may want to check the resistance of that 12VLCD to see what the reading will show compare to your old board. I hope you can return this defective board.

[whatusername]

Re: Toshiba 37" inverter board failure

not sure what u mean check the resistance of the 12vlcd but yes i can return the board but them im stuck in the same place where we left off because i couldnt find what u asked for.. i was hoping to make a good board out of the 2 if i could do that then it would be worth the 55 i paid for it (to me at least) becaus all that tedious trouble shooting that got me stuck will be bypassed

[whatusername]

Re: Toshiba 37" inverter board failure

my only option themn would be to ship the old board to you have u fix it and pay u for the repair and send this one back to the seller.. Would that be an option u would consider?

[budm]

Re: Toshiba 37" inverter board failure

not sure what u mean check the resistance of the 12vlcd but yes i can return the board but them im stuck in the same place where we left off because i couldnt find what u asked for.. i was hoping to make a good board out of the 2 if i could do that then it would be worth the 55 i paid for it (to me at least) becaus all that tedious trouble shooting that got me stuck will be bypassed

We know that we have shorted circuit in the 12VLCD section that we were trying figure out what went wrong in that section, we removed the shorted cap and the Zener diode but we cannot get the 24V at the input put of the buck converter IC.
If you are going to remove the good known IC Q860 and install it into your new board, you need to find out what that added on resistor is for. Is it fusible resistor or what it is used for?
I do no have much spare time to dedicate in fixing your old board, I would like to try but time is the problem.

[whatusername]

Re: Toshiba 37" inverter board failure

ok i understand the time restraint .. and as stated the added on resistor is soldered on to the zener diode my guess is the diode blew and instead of replacing it he soldered a resistor to it to make it work.. he also has replaced a few smd caps u can see in the pic i uploaded yesterday... so i think the resistor was an i dont have the part fix..

[budm]

Re: Toshiba 37" inverter board failure

Yes, but that mod does not work because the 24V is not working with the load (inverter board). I think he thought he fixed the board with that mod but did not install it into the TV or even put on dummy load to find out if it can handle the load. You will need to put that section back to the original condition as your original board, and who knows what else is not properly done to this board.

[whatusername]

Re: Toshiba 37" inverter board failure

ok so i swapped the power ic and ur right i should swap the zener diode too

[whatusername]

Re: Toshiba 37" inverter board failure

ok well i replaced them both and tested the board alone and now have 5v standby
so gonna install in tv and see what happens.. wish me luck

[whatusername]

Re: Toshiba 37" inverter board failure

ok so the only difference is now i get 5v when before i didnt... i still get a declining 2.5v on 12v and 24v is only 1.8v

[budm]

Re: Toshiba 37" inverter board failure

Well it is worst than you original board. May be you can transfer the parts for the 12VLCD section of the new board to the old board.

[whatusername]

Re: Toshiba 37" inverter board failure

yea im gonna have to undo everything i just did.. i will do it tomorrow and what parts would u recommend i swap over?

[budm]

Re: Toshiba 37" inverter board failure

The IC, the cap and the Zener diode as shown in the 12vlcd diagram, I hope you can locate that IC on the board which we could not find last time.