Convergence Problem

Hey guys,

Model: Toshiba TP61H60 rear projection TV
Age: approximately 6 years

I just replaced both STK392-110 ICs. No change in the convergence
problem. I can't adjust the convergence any better than it is now.

I took some pictures of the screen image:
http://www.arcadeguy.net/Toshiba1.jpg
http://www.arcadeguy.net/Toshiba2.jpg
http://www.arcadeguy.net/Toshiba3.jpg

What should I look at replacing or adjusting next??

Thank you,
Tom

 

Probably one or more output resistors are open; usually small value 1 watt...

 

BWL stated:

Hmmm...and those resistors are located where? No problem replacing them,
just knowing which ones. I am working without schematics or manual.

I was going to replace capacitors in the area of the STK's as my next step
since I didn't even consider resistors going bad.

Thank you,
Tom

 

There are numerous resistors in the same physical area as the STK devices.
Check each one and compare those on one circuit withthose in another. If in
doubt you may want to have a professional have a go at the tele. Or at least
buy the service manual or a SAMS Photofact.

 

Art stated:

Great idea...I'll start on that tomorrow. Am I going to be able to check
these resistors in circuit? Do you know if this set is capable of
generating test patterns? I went into service mode but couldn't get a
pattern to come on.

I did find the service manual online for $20, so that is going to happen.

--
Robotron Tom *remove nospam to email*
See the Flashback Arcade at: http:// www.arcadeguy.net

Standing for right when it is unpopular is a true test of moral
character.
-M. Smith

 

Will the affected color(s) convergence adjust vertically and
horizontally? If they do , resistors probably are NOT the problem, you
could be looking at a bad yoke (only saw it once) or a bad DCU. Pull the
affected yoke and look for evidence of arcing/burning.
bubbajim

 

Agreed, Bubba: Toshiba has encountered a fair number of defective yokes,
that can be easily diagnosed by doing a DC resistance or even ringing them.
The DCU is another possibility but almost as rare as the yokes.

 

Subject: Re: Convergence Problem

I've changed plenty of Toshiba yokes. The ones that show physical damage
usually cause shutdown, so ringing or scoping the signal is the best option.
I've also seen bad DCUs and corrupted eeproms in these models.

John Del
Wolcott, CT

"I'm just trying to get into heaven, I'm not running for Jesus!"
Homer Simpson

(remove S for email reply)

 

BubbaJim stated:

Yes, I am able to make both adjustments on the blue, which is the problem
gun. Now, what is a DCU? I haven't heard mention of this acronym yet.

Thank you,
Tom

 

Art stated:

Okay, what the heck is 'ringing'? That is definately a new one on me.

Thank you,
Tom

 

John Del stated:

Sorry, I just remembered that after this blue skew came about, sometimes
the whole picture would do a kind of wide angle jump. It made the picture
look a bit wider and it would only happen for a few seconds then go back
to a normal size image. This affected all colors.

Does that indicate another problem or could it be a part of this problem?

Thank you,
Tom

 

Or just swap the plugs with one of the other yokes and see if the problem
stays with the same color.

 

Using a flyback "ring tester" essentially injects a signal and counts the
number of times an inductor resonates. A shorted turn will kill this
resonation very quickly.

Should be ok with a DC ohms test though.

 

James Sweet stated so wisely:

HEY...great idea!

Now...I read somewhere that these projectors don't hold a charge like a
CRT. Will I need to discharge it before removing??

Thank you,
Tom

"That man is richest whose pleasures are cheapest."
-Henry Thoreau

 

James Sweet stated so wisely:

Ahhh...I don't have that kind of equipment, as you've probably guessed.

And what Ohm range should a good flyback be?

QUESTION: Is there a chance that this <gun> might be low on fluid?
I apologize for not knowing the proper term for this component. Could you
please correct me on the nomenclature?

I do have a scope(although not very versed on it's usage), is there
something I could check that will narrow this down quickly with it?

Thank you,
Tom

"That man is richest whose pleasures are cheapest."
-Henry Thoreau

 

They're CRT's like any other and can hold a charge, but you're just dealing
with the yokes, not the HV, don't worry about it. You're more likely to
shock yourself trying to discharge the CRT's than if you just leave that
part alone.

 

James Sweet stated so wisely:

AAaahhh...now I get it. I misunderstood you the first time. That is a
simple check. I'll check it and get back here to let you know.

Thank you,
Tom

"That man is richest whose pleasures are cheapest."
-Henry Thoreau

 

If you ever start repairing more TV's and stuff you can pick one up for
under $50, they're pretty simple instruments.

Flyback? I thought we were talking about yokes? You generally can't test a
flyback with an ohm meter, good ones are all over the map.

The CRT could be low on coolant, but that'd be easy to check by just peering
down the lense with a flashlight, if it's low it should be obvious.

Not really, a scope is only useful if you know what to expect so you can
compare it to what you see.

 

James Sweet stated so wisely:

This is a project and money saver for my retired dad, so not likely.

Yes, my mistake.

Okay, the CRT doesn't appear to be low on coolant. I did look inside
through the lens with the set on. Knowing that the skew was on the left
side of the screen, I looked into the lens of the blue CRT and on the
right side and I could see the skew very well. (It looked as if a sheet
of clear (or blue) plastic was in there and it had an upward curve in
that area as if it had been heat warped. I realize there isn't a sheet of
plastic in there, that's just what it looked like.

I replace the front screen and tried the user convergence adjustment
again and the blue + that is usually over the white(red/green/blue) +, is
way over at the left edge so that I can only see the right tip when I
move it to the right as far as it will go. I can see that tip move
up/down/left/right, although if I move it left, the tip disappears.

So...anymore ideas or information you need to help diagnose this?

If the CRT is bad, what will a replacement cost me?

Thank you,
Tom

"That man is richest whose pleasures are cheapest."
-Henry Thoreau

 

The CRT is fine, it's lighting up, so at any rate it's not the cause of this
problem. If the yoke is bad, who knows, you might be able to repair it or
find a good used one. The yoke could be fine though.