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Sony KV-32S40 Horiz. Drive Problem

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Chris F.

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Oct 5, 2010, 7:35:39 PM10/5/10
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This set is proving to be a tough fix. I picked it up in the trash a while
ago, and when I first tried it everything seemed to work fine. After about
half an hour though the picture went very dark and shrunk in on the sides.
The problem is permanent now and will not go away. All voltages on the
secondary of the flyback - HV, CRT filament, etc. are about 30% below normal
but the B+ is a solid 136V. All voltages from the power supply are good, and
there are no bad caps... it seems like the horiz. drive signal isn't strong
enough. I tried replacing the horizontal driver transistor as well as all
electrolytics in that area, and fixed some cold solder as well, but it made
no difference.
Any ideas?


Mark Zacharias

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Oct 5, 2010, 8:12:33 PM10/5/10
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"Chris F." <zapp...@hotmail.com> wrote in message
news:4cabb64e$0$14790$9a56...@news.aliant.net...

Did you resolder the horizontal drive transformer?

Mark Z.

hr(bob) hofmann@att.net

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Oct 5, 2010, 11:25:07 PM10/5/10
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On Oct 5, 7:12 pm, "Mark Zacharias" <mark_zachar...@sbcglobal.net>
wrote:
> "Chris F." <zappy...@hotmail.com> wrote in message

After you run the set for a few minutes, turn it off and see how hot
the horizontal/flyback transformer is. If it is scorching hot, there
may be a shorted turn on the transformer, that will cause what you are
seeing..

N_Cook

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Oct 6, 2010, 3:53:48 AM10/6/10
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Chris F. <zapp...@hotmail.com> wrote in message
news:4cabb64e$0$14790$9a56...@news.aliant.net...

Sometimes a failing/ed non-polarised capacitor in the flyback area causes
that problem


Mark Zacharias

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Oct 6, 2010, 7:02:34 AM10/6/10
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"hr(bob) hof...@att.net" <hrho...@att.net> wrote in message
news:a7592161-f954-4fa8...@h7g2000yqn.googlegroups.com...


I think if that were the case, the horizontal output transistor would have
died in short order. Of course, the bad solder at the drive transformer,
which is VERY common, can and does kill the output transistor also; I was
just thinking the OP had been lucky up to this point.

Mark Z.

Meat Plow

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Oct 6, 2010, 8:36:37 AM10/6/10
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NP tuning caps? Cold solder flyback pins?

--
Live Fast, Die Young and Leave a Pretty Corpse

John Ferrier

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Oct 6, 2010, 6:27:05 PM10/6/10
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"Meat Plow" <mhy...@yahoo.com> wrote in message
news:pan.2010.10...@lmao.lol.lol...

Try the G2 rectifier diode and it's feed resistor you will probably find
tracking marks under the components.

>


Stefan Heimers

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Oct 8, 2010, 8:32:34 AM10/8/10
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Chris F. wrote:


> Any ideas?

Resolder all power semiconductors which are mounted on heat sinks or the
metal frame of the chassis.

Stefan

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