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didaschi
Joined: 27 Jan 2009
Posts: 47
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| Posted: Sat Jul 12, 2025 6:04 pm Post subject: Sony G70 test raster Green tube collapses above left |
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Hello, the green tube on my G70 has a problem.
In a test image, the raster collapses in the upper left section. There are jittery lines that bend significantly toward the bottom left center. Additionally, two lines in the middle are jittering.
It also seems that one line has become two.
No matter how I change the keystone and pincushion settings, I can only minimize the jitter in the horizontal range but not completely eliminate it.
I can't set a straight horizontal line at the top edge.
It's possible with red and blue without any problems.
The device sat unused in the basement for about a year and a half and worked perfectly before.
The problem occurs with all input types, but most severely with RGB.
Do you have any ideas?
Best Regards
didaschi
[img][/img]
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Sat Jul 12, 2025 10:57 pm Post subject: |
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WHile I've been out of the CRT game for 7-8 years, all these sets are now showing problems that I've never seen before, and I worked on 50-60 G70s back in the day.
The convergence output drivers are on two large STK392-220 chips on the convergence board. They were notorious for failing even when I was working on them, and they are long discontinued. Any one you'll find on eBay is a Chinese counterfeit, unless you're REALLY lucky. They overheat, the leads coming out the bottom get brittle, and break off as you try to unsolder them. That would be my best guess as to the problem.
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didaschi
Joined: 27 Jan 2009
Posts: 47
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| Posted: Sun Jul 13, 2025 9:10 am Post subject: |
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Hello Curt,
thank you for your prompt try to help.
Yes it is the convergence board.
I changed the board (out of a second G70 I have) and it runs perfect.
Is it possible to locate the defect STK Chip, left or right one? Or shall I change both?
So now I have to try to find good STK Chip.
on Amazon Germany I see such a Chip produced from Lumonic. Do you know that Company? Is it from China?
didaschi
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didaschi
Joined: 27 Jan 2009
Posts: 47
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| Posted: Mon Jul 14, 2025 11:14 am Post subject: |
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Hello,
there are two STK392-220. One for hor. and one for vertical Sync.
Is only the hor. Sync demaged and shall I first change that STK392 and test?
Best Regards
didaschi
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Thu Jul 24, 2025 2:49 pm Post subject: |
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Change them both. I haven't seen an original 392-220 in 10 years. All you can do is try them, and see if they work. It's the weak point of the G70 though.
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