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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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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 |
#2
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BWL stated:
Probably one or more output resistors are open; usually small value 1 watt... 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 |
#3
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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. "Tom" wrote in message ... BWL stated: Probably one or more output resistors are open; usually small value 1 watt... 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 |
#4
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Art stated:
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. 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 |
#5
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Robotron Tom wrote in
: Art stated: 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. 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. 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 ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#6
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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. "BubbaJim" wrote in message . 40... Robotron Tom wrote in : Art stated: 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. 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. 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 ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#7
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BubbaJim stated:
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 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 |
#8
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Art stated:
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. Okay, what the heck is 'ringing'? That is definately a new one on me. Thank you, Tom |
#9
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John Del stated:
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 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 |
#10
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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 Or just swap the plugs with one of the other yokes and see if the problem stays with the same color. |
#11
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"Tom" wrote in message ... Art stated: 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. Okay, what the heck is 'ringing'? That is definately a new one on me. 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. |
#12
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James Sweet stated so wisely:
Or just swap the plugs with one of the other yokes and see if the problem stays with the same color. 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 |
#13
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James Sweet stated so wisely:
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. Ahhh...I don't have that kind of equipment, as you've probably guessed. Should be ok with a DC ohms test though. 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 |
#14
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"Tom" wrote in message ... James Sweet stated so wisely: Or just swap the plugs with one of the other yokes and see if the problem stays with the same color. 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?? 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. |
#15
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James Sweet stated so wisely:
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. 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 |
#16
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"Tom" wrote in message ... James Sweet stated so wisely: 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. Ahhh...I don't have that kind of equipment, as you've probably guessed. If you ever start repairing more TV's and stuff you can pick one up for under $50, they're pretty simple instruments. Should be ok with a DC ohms test though. And what Ohm range should a good flyback be? 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. 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? 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. 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? Not really, a scope is only useful if you know what to expect so you can compare it to what you see. |
#17
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James Sweet stated so wisely:
If you ever start repairing more TV's and stuff you can pick one up for under $50, they're pretty simple instruments. This is a project and money saver for my retired dad, so not likely. 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. Yes, my mistake. 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. 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 |
#18
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If the CRT is bad, what will a replacement cost me? 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. |
#19
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"Tom" wrote in message ... James Sweet stated so wisely: If you ever start repairing more TV's and stuff you can pick one up for under $50, they're pretty simple instruments. This is a project and money saver for my retired dad, so not likely. 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. Yes, my mistake. 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. 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 Oh I forgot to say, check the resistance of the good yokes and compare it to the questionable one. |
#20
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James Sweet stated so wisely:
Oh I forgot to say, check the resistance of the good yokes and compare it to the questionable one. I'll get to this and report back. Thank you, Tom "That man is richest whose pleasures are cheapest." -Henry Thoreau |
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