[TechAssist] Re: SONY KV-27TS32
- From: "Peter oliver" <oliver_peter1@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Tue, 01 Jul 2003 03:14:42 +0000
Definately an odd one as Lenoard said it is usually one or the other. Sony's
litrature seems to indicate (if I read it correctly) that the VDR's primary
purpose is to protect the transformers from over voltage when the chopper
transistors fail. Hence VDR standing for voltage dependant resistor,
Essentialy a MOV (metal oxide varistor) that only conducts after a certian
voltage threshold is reached although in that set they may be using it to
control the firing of the start up transformer. I have seen tips for, but
never have had to (fortunatly), replacment of some of the small ceramic
caps in the circuit- possiblly they could be altering the waveform and
causing a spike or wave form anonomoly or as was proposed the FBT could have
an internitnat thermal fault but hypothetically it should have a propensity
to kill the HOT again. Another possibility would be a bad batch of parts???.
One other off the wall thought that came to me would be to check the
vertical IC connections in the remote possibity that the connections are
poor sending an irregular sync pulse into the Horz or Pin timming. PC board
cracks?
Peter Oliver
Tucson Radio TV
From: "Leonard Caillouet" <lcaillo@xxxxxxxxxxxx>
Reply-To: techassist@xxxxxxxxxxxxx
To: <techassist@xxxxxxxxxxxxx>
Subject: [TechAssist] Re: SONY KV-27TS32
Date: Mon, 30 Jun 2003 21:49:29 -0400
I fix these all the time and rarely find a bad VDR, especially when the HOTs
are bad. Occasionally there is a bad cap in the primary of the supply, and
all of them should be checked. The diodes should be lifted and checked out
of circuit as well if you are having repeat failures. Verify that the duty
cycle of Q601 and Q602 is 50% +/- a couple of percent when starting it up
very slowly.
Are you sure that VDR601 was bad? If you checked it in circuit b/f you
removed the shorted transistors it would have read short. If the HOT was
the cause of the PS failure, the VDRs are usually OK and the root cause of
the problem is usually in the H drive circuit.
Like everyone has said, make sure that you resolder the HDT well.
Leonard Caillouet
Electronics World
Gainesville, FL
----- Original Message -----
From: "Intrepid Video Support" <support@xxxxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Monday, June 30, 2003 9:04 PM
Subject: [TechAssist] Re: SONY KV-27TS32
> Medi,
> I've been told all the VDR's should be replaced. At their low price, it
shouldn't break you, but maybe add
> reliability.
>
> Jeff Dougherty
> Intrepid Video TV/VCR
> 263 S Front St
> Steelton PA 17113
> fax...717-564-4952
> www.intrepid-video.com www.tech-repair.net
>
> ----- Original Message -----
> From: "Nova Service Center" <techassist@xxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Monday, June 30, 2003 4:32 PM
> Subject: [TechAssist] SONY KV-27TS32
>
>
> Hi Everyone
> The customer complaint was that the Sony TV ( Model # KV-27TS32 ) was
dead
. I found 2 regulators (
> 2sc4834 ) and horizontal output transistor ( 2sc4927 ) were short. Also
.1
ohm resistor was open and VDR
> 601 was bad. replaced all tv turned on and worked for 10 minutes. The a
big sound and all the parts except
> VDR 601 went bad again. The VDR 602 and 603 looks good.I don't know what
I
am missing . Any suggestion
> would be appreciated.
> Nova service Center
> 240-632-2994
> Medi
>
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