On 03/12/11 22:18, Sylvia Else wrote:
This TV died abruptly, and completely without warning, while it was
turned on. It appears completely dead, other than than that the
degaussing still works.

There was some burning smell evident immediately after it failed, but
nothing has obviously suffered heat trauma.

Presumably there's a problem with the power supply, which looks like a
switch-mode. One thing I've noticed is that when power is connected, it
emits a clicking noise - about three times a second. When the power is
disconnected, the clicking doesn't stop immediately but continues for
several seconds, slowing down.

The clicking noise isn't coming from the speakers. I assume it's coming
from a transformer or choke.

A friend and I (he very experienced) tries to fix a similar fault in a
similar Sony TV a year back. The clicking was coming from a relay in the
PSU, which appears to be driven via some circuitry from an opto-isolator
from the main board. It would appear that it would try to power up, detect
a fault, and shut off again, repeatedly. We never did get to the bottom of
it. Really, with so many rather good glass TVs on the nature strip, are you
sure it's worth the trouble?

Clifford Heath.

On 13/03/2011 4:28 PM, Clifford Heath wrote:
Really, with so many rather good glass TVs on the nature strip, are you
sure it's worth the trouble?

Probably not, particulary as I've identified a dud transistor that is
moderately expensive to source, and whose failure may only be a symptom.
If the problem had been a failed electrolytic capacitor that I could get
from my local electronics shop, then it would have been worth having a
go at fixing it. As things stand, it's destined for the tip (or
something - see below).

But we don't get good glass TVs on the nature strip, at least not in my
suburb. The council banned getting rid of them that way (i.e. leaving
them out on an official council cleanup day), with the result that one
cannot simply go out on such a day, and pick up a TV whose only sin is
that it isn't wide-screen.

Sylvia.

On 03/13/11 16:44, Sylvia Else wrote:
Probably not, particulary as I've identified a dud transistor that is
moderately expensive to source,

I replaced the HOT in this TV also. $9 including shipping from WES.
However, HOTs are very strange devices. If you just do the basic
two-diode test, you'll probably consider that a good one has failed.
That's what I did ... something to keep in mind.

But we don't get good glass TVs on the nature strip, at least not in my
suburb.

So drive to the next suburb. Aforementioned friend has picked up
half a dozen perfectly functional TVs that way, usually wide-screen
versions (he prefers those), and provided them to friends. Must get
a few duds, but you can drop those back.

Clifford Heath.

On Mar 13, 3:28*pm, Clifford Heath wrote:
On 03/12/11 22:18, Sylvia Else wrote:

This TV died abruptly, and completely without warning, while it was
turned on. It appears completely dead, other than than that the
degaussing still works.

There was some burning smell evident immediately after it failed, but
nothing has obviously suffered heat trauma.

Presumably there's a problem with the power supply, which looks like a
switch-mode. One thing I've noticed is that when power is connected, it
emits a clicking noise - about three times a second. When the power is
disconnected, the clicking doesn't stop immediately but continues for
several seconds, slowing down.

The clicking noise isn't coming from the speakers. I assume it's coming
from a transformer or choke.

A friend and I (he very experienced) tries to fix a similar fault in a
similar Sony TV a year back. The clicking was coming from a relay in the
PSU, which appears to be driven via some circuitry from an opto-isolator
from the main board. It would appear that it would try to power up, detect
a fault, and shut off again, repeatedly. We never did get to the bottom of
it. Really, with so many rather good glass TVs on the nature strip, are you
sure it's worth the trouble?

Clifford Heath.


We had a nice 2004 vintage Sharp set that failed about a year back.
Intermittent, wouldn't turn on sometimes but would other times.
had a fast look inside and saw corrosion around one of the IC's.
(looked like the CPU).

The set only just fit into the wheely bin, but it did fit. Saved a
trip out to the (isolated) main road to leave it for someone to take
home.

"Clifford Heath"

However, HOTs are very strange devices. If you just do the basic
two-diode test, you'll probably consider that a good one has failed.
That's what I did ... something to keep in mind.


** You need a " Power Transistor Tester" - published as a full construction
article in EA magazine back in May of 1988 by me. Altronics and Jaycar had
kits for it at one time.

It will reasonably accurately test the beta (or Hfe) of any power transistor
OR power Darlington pair OR horizontal deflection transistor. Very cheap
to make - uses only a few passives, a couple of red LEDs and a WW pot.

No PCB was used as it take only minutes to wire up the bits once they are
all fitted into a small jiffy box.

It will also allow close matching ( ie Vbe match) of groups of power
transistors that must operate in parallel.

Requires an external 12 volt DC source.

I would post the schem on ABSE, but like so many others I no longer have
access to the site.




..... Phil

On 03/14/11 17:44, Phil Allison wrote:
** You need a " Power Transistor Tester" - published as a full construction

Thanks.

I would post the schem on ABSE, but like so many others I no longer have
access to the site.

You mean you have no access to ABSE? Spend $US3.95 at www.teranews.com and
get free lifetime access to all the binary groups, limited to 50MB/day.

Clifford Heath.

"Clifford Heath"
Phil Allison wrote:

** You need a " Power Transistor Tester" - published as a full
construction

Thanks.

I would post the schem on ABSE, but like so many others I no longer have
access to the site.

You mean you have no access to ABSE? Spend $US3.95 at www.teranews.com and
get free lifetime access to all the binary groups, limited to 50MB/day.


** Not worth a hoot to me for posting schems or pics unless everyone has the
same.



...... Phil