Blown HOT in Sony KVT-29SZ1

[ap]

I have a Sony KV 29SZ1 that has a blown HOT. It is owned by my
apprentice who doesn't have a great deal of cash to throw around, so I
told him to bring it into work and we would have a go at fixing it.

The fault was simple, would not turn on. I opened it up and put the
meter across B+ - 0v. I could also hear it ticking. So the first thing
I did was pull out the HOT and test it, sure enough it was SC. I sent
the the young fella out to buy a new HOT which turned out to be AU$30.

So, the question I ask is: Is there in easy way to tell if the LOPT is
the reason the HOT has failed? I don't really want to put the new part
in if it is going to blow straight away. I was thinking about putting
it in and bringing up the power slowly from a variac. Will this help?

TAI,

AP

 

[Art]

Ringer Testing of the LOPT should convince you if indeed it is operational
or defective. Commercial instruments are available to do the task. Inspect
the main circuit board to confirm the solder connections at the horizontal
driver transistor and transformer as well as those at the LOPT itself.
Confirm the B+ is correctly regulated at the appropriate voltage. ESR the
caps in the set, esp in the power supply circuits.
"ap" <nospam@nospam.please.thankyou> wrote in message
news:er2s809v2427je48utttonbpt4of4ip947@4ax.com...

I have a Sony KV 29SZ1 that has a blown HOT. It is owned by my
apprentice who doesn't have a great deal of cash to throw around, so I
told him to bring it into work and we would have a go at fixing it.

The fault was simple, would not turn on. I opened it up and put the
meter across B+ - 0v. I could also hear it ticking. So the first thing
I did was pull out the HOT and test it, sure enough it was SC. I sent
the the young fella out to buy a new HOT which turned out to be AU$30.

So, the question I ask is: Is there in easy way to tell if the LOPT is
the reason the HOT has failed? I don't really want to put the new part
in if it is going to blow straight away. I was thinking about putting
it in and bringing up the power slowly from a variac. Will this help?

TAI,

AP

 

[John Del]

Subject: Blown HOT in Sony KVT-29SZ1
From: ap nospam@nospam.please.thankyou
Date: 4/27/04 7:37 AM
Message-id:

I was thinking about putting

it in and bringing up the power slowly from a variac. Will this help?

No. SMPSs will output the full voltage when the bridge voltage passes the
excite threshold (typically 80 volts or so). So it's pretty much all or
nothing.

A ringer will pick up many trans defects, but make sure you at least check the
tuning caps on the collector of the HOT to ground. A bad one here will smoke
the new output as fast as a bad LOPT.

John Del
Wolcott, CT

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

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