Toshiba 42H81: Convergence repair?


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Toshiba 42H81: Convergence repair?

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SpikeDmax
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Nov 29, 2009, 5:25 AM

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Toshiba 42H81: Convergence repair?	Can't Post

Hello, I'm new here and looking for repair help on a 2001 Toshiba 42H81 projection TV. I've been reading all I can and it sounds like I have convergence issues, getting double blue/red images as well as distorted lines. From what I've read I believe I need two STK 392-150 chips? I've never tore into a tv before but have built computers and have experience soldering inferred motion activated cameras so I'm willing to dive into this and try and repair it, if it doesn't go well nothing lost.

So, my question is where do I start? Where are the convergence chips? Please start basic and make this as simple as possible for me as this is very foreign to me but I'm willing to learn.

Here's the television...

Here's the inside from the back of the tv...

Closer view...

techchris
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Nov 29, 2009, 10:22 AM

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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

the ic's are screwed to the big finned heatsinks to the right of the flyback transformer in the centre of your picture, under the black plastic bracket. there are screws around the edge of the board to take out so the panel can be removed.take a picture of the board first so you know where all the connecting wires go when you reassemble it. unsolder the ic pins and fit new ones. dont forget to use new heat compound between the ic's and the metal if it has been used by the manufacturers when new.there are usually a couple of low value resistors nearby which may have gone open circuit when the ic's failed,so check and replace at the same time.

SpikeDmax
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Nov 29, 2009, 6:25 PM

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Re: [techchris] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Okay, think I understand....remove board (take out screws along the edge) and any connecting wires (photo first for reassembly purposes). The chips are under the silver 'z' patterned heat sink (which is under the black bracket)? I'm assuming once I get that done the chips will be easy to identify? Are there only two? Will I visually be able to tell if the resistors are bad, blown?

Thanks for you help. I'm kind of looking forward to the challenge of doing this, have a feeling it wont be easy however.

techchris
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Nov 29, 2009, 7:25 PM

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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

the chips are marked STK.....screwed vertically to the side of the heat sink. you will need a multimeter to check resistors, they measure between 3 and 5 ohms approx.I dont have schematic diagram for this model so cannot give you the R number on the board. if you work methodically it is not difficult to do the job.

SpikeDmax
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Nov 29, 2009, 7:27 PM

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Re: [techchris] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Thanks. Will try to start on it today and post some pics that might help someone else down the road...shame so many just throw their tv's away when they can be fixed.

SpikeDmax
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Dec 6, 2009, 8:54 PM

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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Okay, now what? Help!

I got the board out and see the STK chips on the back of the heat sink but how do I get to them? Do I need to un-solder the heat sink or the board that is blocking access to the chips?

SpikeDmax
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Dec 7, 2009, 12:31 AM

Post #7 of 253 (18451 views)
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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Got it! I had to unsolder the board blocking access to the IC screws but once I did that and removed it I could unscrew the screws holding the chips to the heat sink. I then unsolder the IC's and got them out.

Next question where are the resistors and what do they look like? Might as well replace them since I've got it apart.

Also, is Audio lab still the best place to get parts? Should I replace the STK392-110 with STK392-150? Believe I read here that the 150's are better....thoughts?

SpikeDmax
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Dec 7, 2009, 7:22 PM

Post #8 of 253 (18436 views)
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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Can anyone help on the questions above??? I'd like to get some parts ordered but want to make sure I do it right.

Thanks

jts1957
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Dec 8, 2009, 7:22 AM

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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Quote

Next question where are the resistors and what do they look like? Might as well replace them since I've got it apart.

You should only need to "check" them with a DVM, unsolder and float one side if reading in doubt. I believe I last "seed" them under the fins of the heat sinks. Multiples of two different values, if memory serves.

Quote

Also, is Audio lab still the best place to get parts? Should I replace the STK392-110 with STK392-150? Believe I read here that the 150's are better....thoughts?

Don't know about Audio lab. I've always believed: Put back in what you took out.

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Location: Far, Far Away

SpikeDmax
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Dec 8, 2009, 5:11 PM

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Re: [jts1957] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Would this be the resistor? http://www.audiolabga.com/images/resistor_flameproof.jpg If so, there is one that looks like it has a bulge to it or something protruding out its side and also appears to have black or darkened rings around it. I haven't tested it yet with a dvm but does it sound like it's probably blown? 

Also, on audiolabs website there are several different ratings for resistor levels like 1/4 watt, 1/2 watt, 1 watt and 2 watt....any suggestions on what I would need to get?

(This post was edited by SpikeDmax on Dec 8, 2009, 5:13 PM)

jts1957
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Dec 8, 2009, 8:36 PM

Post #11 of 253 (18414 views)
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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

I'd pull it and test it if it doesn't "fall apart" as you handle.

Replace with equal (or bigger) wattage (if space permits). Physical measurements for each wattage should be available through a resistor manufacturer's website.
http://www.ohmcraft.com/

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Location: Far, Far Away

SpikeDmax
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Jan 10, 2010, 10:08 PM

Post #12 of 253 (18317 views)
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Re: [jts1957] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Well, my first tv repair is a failure. I replaced both convergences and resistor put everything back together and turned the tv on and the picture looks the same as before...ghoast images and mostly red and blue colors. Also, I don't have "menu" capabilities anymore. I tried doing an convergence alignment by pressing the mute button twice on the remote and the menu button on the tv like I've done before to bring up the alignment lines but that is no longer working.

Anyone want to help before I give up and take it to the dump? Please.

allykat24
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Jan 11, 2010, 7:48 PM

Post #13 of 253 (18301 views)
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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Hey Spike, I have the exact same problem with my 42H81. I changed out both of the stk392's, hooked everything back up and plugged it back in. No picture or sound and the red power light flashes. I did this repair a week ago and read thru hundreds of threads & can't find a solution. Frustration has taken its toll and I have since dragged the SOB upstairs to be taken to the dump also, but not quite ready to give up. I feel your pain & will be watching your thread to see how everything turns out.
Best of luck to you and don't quit!!

SpikeDmax
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Jan 11, 2010, 8:44 PM

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Re: [allykat24] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Ah, misery loves company...lets figure this out together. Smile

I have since I posted been able to get into manual mode for aligning convergence but can't figure out how to align the projection lamps. Stumped! I'm thinking a problem with my tv is a blown green projector. Anyone know how common that might be or possibility?

Did you check your board for blown resistor(s)? Double check your soldering and connections?

Hang in there, we'll get it....or go insane trying. Pirate

jts1957
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Jan 12, 2010, 2:28 AM

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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

First off, were talking a 3 CRT rear projection set. Red/Green/Blue CRT projects image onto a mirror which reflects it onto the screen. All three tube faces should be lit.
If you've changed the convergence ICs and a resistor, you shouldn't be doing ANY adjustments to ANY of the CRTs (Projection lamps, as you're calling them)! Mad

Further, if the set WAS in alignment and properly converged BEFORE you replaced the parts, very little (if any) auto/manual/service convergence adjustments should be required once you get the convergence circuits working.
Just a thought: do you have correct power reaching those ICs? I can't recall if they used circuit protector/fuses/nothing in between power supply and the Convergence.

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Location: Far, Far Away

allykat24
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Jan 12, 2010, 6:45 PM

Post #16 of 253 (18274 views)
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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Spike, What resistor did you change out? Jts1957 had mentioned that the resistors where under the heat sink fins. I have everything back apart Crazy

and checked what I thought were the resistors but they only checked out at 1.8. Do you have a picture of what one you changed? I think the wife is ready to kick me and the tv out to the curb! Thanks.

SpikeDmax
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Jan 12, 2010, 8:59 PM

Post #17 of 253 (18271 views)
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Re: [allykat24] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Check this thread...

http://www.tv-forums.com/cgi-bin/gforum.cgi?post=61898;#61898

JTS1957 is a one man show and a big help

jts1957
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Jan 13, 2010, 3:25 AM

Post #18 of 253 (18263 views)
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Re: [allykat24] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

They all have to be checked and they all have to measure in range (1.8 ohms = 1.7 to 1.9 is acceptable - 3.0 is NOT). Wink

(If necessary unsolder one side of each resistor and measure it out of circuit.)

Check:
R7710, R7715, (220 ohms 2 watt) et al
and
R7711, R7716, (1.8 ohms 1 watt) et al

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Location: Far, Far Away

Gus67
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Jan 13, 2010, 4:05 AM

Post #19 of 253 (18259 views)
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Re: [jts1957] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Man it sucks throwing parts at something and still not fixing it.

One suggestion before freaking out...(take a step back...think for a moment) and look for simple mistakes you may have made.

Check all your solder joints and the connections to the heat sink in respect to the component you swaped out

Is the heat sink isolated from the component, or making a path to ground? is it suppose to be floating,or grounded? is there a mica washer and heat transfer grease on the component?is the screw you used to attach the heat sink isloated from the component?

Also,

Spend a few min.tracing all the tracks on the board that you soldered.Sometimes when you remove a component that has a number of legs, you will tear a track on the board due to not having all of the legs free from the board.It's easy to remove a component with only 2 or 3 legs.When you have something that has numerous legs you may tend to pull the component out,and in doing so,damage the tracks and the thru holes.So when you replace the component you may not have a good solid connection.

one more,

In one of these posts,I believe I read you commented on a bulged resistor...are you sure it's a resistor?..maybe it's a blown Cap? and if so,what caused the damage...maybe something other than what you are looking at.

.

allykat24
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Jan 14, 2010, 3:12 AM

Post #20 of 253 (18239 views)
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Re: [jts1957] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

All the resistors check out at 1.8. One of my friends at work said his dad had projection tv with a blinking power light and it was the bulb. Is this a possible problem with my tv? Thanks guys for all your help and patience.

jts1957
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Jan 14, 2010, 3:37 AM

Post #21 of 253 (18238 views)
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Re: [allykat24] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Don't use lamps or bulbs in a CRT set. Tongue

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Location: Far, Far Away

allykat24
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Jan 15, 2010, 5:45 AM

Post #22 of 253 (18212 views)
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Re: [jts1957] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Do you have any other suggestions or tips that I might try? Unimpressed

jts1957
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Jan 15, 2010, 7:09 AM

Post #23 of 253 (18210 views)
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Re: [allykat24] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

F852 & F853? Smile

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Location: Far, Far Away

Loki2012
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Feb 20, 2010, 7:28 AM

Post #24 of 253 (18053 views)
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Re: [SpikeDmax] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

I am about to start repairs on my brothers 42H81 and I appreciate the pictures you posted! How did the repairs go?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"You keep using that word. I do not think it means what you think it means. "

SpikeDmax
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Feb 22, 2010, 7:57 PM

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Re: [Loki2012] Toshiba 42H81: Convergence repair? [In reply to]	Can't Post

Still sitting in the garage.....not working! Been putting off trying again and leaning towards giving up and taking to the dump. I just don't understand this stuff enough to have any conviction of getting it to work. Sorry.

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