Question about Toshiba 43HX70 43" Rear Projection Television

2 Answers

Toshiba 43HX70 convergence fix - now no video

Hi! I've done the old tried and true replacement of the convergence STK ICs and the blue would not adjust horizontally so I also replaced all the resistors. No Help.  I then replaced the two ICs again with new ones. Now I have audio but no video at all.

The service manual mentions the 6 resistors are 1.2 Ohms but I've noticed the 2 on the outside edges appear to be a different color code than the other 4. The video still worked after changing resistors but didn't work after changing out the ICs again. Any idea what could be causing my 'no video' issue now?

I suspect I could've also blown a fuse (high voltage?) and if that causes no video, any idea where the fuse(s) are?


Thanks in advance!

Posted by bman63 on

  • 1 more comment 
  • bman63 Nov 06, 2007

    Thanks T!

    Was out of town for a bit but ready to start back in on it.

    Any idea if the Pwr Supply is mounted on the main board (the big board on the left when facing the back on the set) or a separate unit? (as with PCs). I read a similar post about (2) 6.3 Amp fuses on the front edge of the pwr supply board causing the 'No Video' issue (after replacing convergence chips).

    Is safety a big concern with removing this main board? The convergence board was no big deal but no power cord running to that one :)

    Any other tips regarding this pwr supply/fuse issue greatly appreciated!


  • bman63 Nov 24, 2007

    Got my parts and tried them...Sure enough - F850/851 were blown. Also shorted the convergence chips and blew one resistor, so replaced them again. Good call!

    Now I have video again but none of the remote controls will power up the set (remotes themselves have new batteries and are working fine). As a result I can't go into service mode and reset convergence...looks like I blew something on the remote sensor.

    I know the infra-red sensor is behind the screen on this model; any idea what I blew and where it's located? I figure if I'm lucky maybe it's a removable fuse, although I don't know where the sensor runs to on the board...Thanks for the help!!

  • Anonymous Jan 29, 2008

    I have the same exact problem!!!

    My tv wasnt bad at all.... I had a little bit of red bleeding off on the right and a little blue bleeding off on the left.... really not a big deal at all.... at most, it just made the sides of the screen a LITTLE blurry.... anyway, Im super picky so I decided to replace the IC's....

    apperantly I bought them from a site that I later found out was the #1 place not to buy the ICs from (electronix - or something like that)

    After installing the ICs, I put everything back to how it was.... and Yes, I have experience in soldering. and I power it on. and I hear the Static sound coming from the power lines.... the Led is solid.... .I hear sound................ but no Video...(Pwned)

    I opened her up... Checked her out, re-touched everything up (my own work) and tried again... .and again... and again. I musta opened her up 4 times or so.... I checked the fuses(while connected) they all seemed fine... Then i thought of just putting back the old ICs... the ones that were working anyway.. and Tried that.... still no video!!!

    Im really loosing hope... I started to call service shops in the area... there talking about $300 plus the price of the ICs which they wanna charge $100 for each.

    My game-plan for tonight is to open her up, de-solder the fuses, check them out while outside of the board... if there good, put them back in... and hope for a miracle.... :'(

    I'll try and keep researching, and i'll post a result soon.... This is a good website so I hope what I find out will help others.




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How do i test the IC chips?...

Posted on Jan 29, 2008


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I think the hardest to solve problems are those I installed!!
Where do we start==no lecture,but I never change a resistor
unless it has changed (in value!) Use a digital meter and check
the value of each resistor.Toshiba is a bit confusing as to values
of each resistor and location in relation to the IC's.Go over your own work first.Check micro fuses in power supply=F851,F852,
etc. Carefully resolder steel jumper wires at board edge,they feed
B+ to convergence amp circuit.Be sure to verify no shorts in pins
of IC's.(use your meter).........T

Posted on Oct 25, 2007

  • Vista Electronics Nov 07, 2007

    Locate on the power board ( the one the AC cord goes into) any

    and all fuses. F850,F851 for example. They are along the board

    edge-- the symptom should be " blinking LED " if a fuse is open.

    Check them all with meter...Also,solder jumper wires on signal

    board = 008,010,017,048 and 600 or you might blow fuses again.............................................................................T.



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