Question about Toshiba 42H81 42" Rear Projection Television

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42H81 Convergence issues

I picked up a 42H81 last week for free locally. I brought it home plugged it in and noticed the convergence was off, maily the red. I had a pair of stk392-110 ICs here and installed them along with the 1.8 ohm 1w resistors. I plugged it in and still no fix.

I'm new to this field but very skilled with an iron and not afraid to try anything.

I noticed while it was on the something smelled like it was getting warm. I looked at the resistors and the very same one that was bad to begin with was getting hot, the colors changed on it. Now, the one thing I did notice was the band that holds the convergence yoke to the tube was off, just hanging there, no bolt in it!! I went to the hardware store and picked one up and installed it. When I first turned it on after installing the amps was the red was shifting before my eyes so I shut it down (couldn't be good). The red didn't shift this time but still didn't fix the issue and the resistor was still getting hot.

This set has 2 main boards and it looks like half of the convergence is on the power board. I did check that side and there is 4 resitors that are out of spec and 1 of them has almost no resistance at all.

Is it possible that the convergence yoke is shorted in some way?

Could I turn this set on with the wires to that yoke dis-connected to find out if that is the source to my problems?

I'm no wiz with these yet but it seems to me (bear with me please) that the STK originally went south and everything powering it took a hit. There is one fuse on that circuit open. Maybe the hit fried that resistors and now that I have changed the parts they are getting too much power?

Thank you for any replies, good or bad.

Posted by on

  • redrobin29 Feb 15, 2009

    I'll have to wait for the resistors to come in for the power board. They should be here tomorrow. The fuse that was popped on the power board isn't a pico fuse and I cannot find it anywhere online, can I replace it with a pico fuse of the same rating?



    I'll post back with my findings.



    Thanks!

  • redrobin29 Feb 24, 2009

    I orderd the new 2sj512 FET that is in front of the resistor that is getting hot and it's still frying that resistor?



    I'll tear back into it and recheck everything again...



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I've seen a few shorted convergence yokes in toshibas. Sometimes after running the TV for a few minutes, you can feel the relative temperature of the 3 yokes to tell which is overheating and therefore shorted. Don't forget to re-check all the low resistance resistors around the convergence ICs to make sure that the are within the 5% tolerance rating they should be. Also on some of these models, there is a jumper wire located near one of the ICs that develops an intermittent solder connection.

michtech

Posted on Feb 15, 2009

  • Billy Bauer Feb 15, 2009

    I've seen a few shorted convergence yokes in toshibas. Sometimes after running the TV for a few minutes, you can feel the relative temperature of the 3 yokes to tell which is overheating and therefore shorted. Don't forget to re-check all the low resistance resistors around the convergence ICs to make sure that the are within the 5% tolerance rating they should be. Also on some of these models, there is a jumper wire located near one of the ICs that develops an intermittent solder connection.



    michtech

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