Hi, I would like to enquire if anyone can give me some advice about a repair
I did for a friend recently.

The TV was a Philips 14PV182/05, which had a tripping powersupply.

I tested most of the electrolytics with my ESR meter, and supprisingly they
all read good.

I tested the HOT - good, but the set worked with it removed. (Sound + VCR)

I isolated all the secondary supplies derrived from the LOPT, but the set
still tripped (HOT in place).

So I presumed a faulty LOPT. This was confirmed by rudimentary ring testing
on my oscilloscope.


I replaced the LOPT with an HR equivilant, and the TV now appears to be
working fine. My question is, weather I should be looking for an underlying
cause for the original LOPT to fail. I did notice that there was some high
frequency sound coming from the TV (Audible with the TV volume turned right
down, and the cover off) - after I replaced the LOPT. This makes me wounder
if everything is A-Ok, but I'm aware that transformers / capacitors can
sometimes make some noise when running normally.

Do LOPTs just fail on their own, or are they usually 'caused' to fail by
another part? I've seen a cople of references to similar symptoms in this TV
(PSU tripping) being fixed by just replacing the LOPT.

Please note that I don't do this for a living or anything, I'm an electronic
engineering student, and only have a few years worth of experience fixing
the odd monitor / TV / SMPS etc. My theoretical knowledge isn't too bad (I
think), but I lack the experience of someone who comes across these faults
day after day.

Thanks for you help

Peter Clifton

Peter Clifton schreef/a écrit/wrote in/dans/in
le/on/op 16/02/2004 :

So I presumed a faulty LOPT. This was confirmed by rudimentary ring testing
on my oscilloscope.

Do LOPTs just fail on their own, or are they usually 'caused' to fail by
another part?

They fail on their own, Peter. Especially in those sets. We replace a
few every week.
The quality of those transformer has dropped dramaticaly.

Sometimes the line output transistor has to be replaced as well and a
little blue capacity, close to that transistor.

Greetz,

--
Alain Beguin http://home.tiscali.be/a.beguin
mailto: http://cerbermail.com/?XiEiqwImaa
MesNews Reader: http://www.zoo-logique.org/mesnews/index-gb.php

Thanks for that - it makes me feel better about the job I did.

Presumably, if the cap or the HOT need replacing then it would show some
visible sign of it when I powered the set up again.
(I hope anyway)

My friend has her TV back now, but if anyone thinks there is still cause to
be concerned or investigate further, I could ask to look at it again.

I love to repair things (and hence work for free - I wouldn't claim to have
a high enough competence or give a high enough success rate to charge like a
pro), but I can see why repairing televisions is becoming uneconomical
nowadays. For a little more than the cost of parts and labour, people can
simply buy a new TV which may (or may not perhaps) have more lifetime in it
than a repaired 6yr old set. The new LOPT was about £20, and a new set was
only £100. Once you add in labour, its getting to be a close call.

Many thanks for your advice

Peter


"Alain Beguin" wrote in message
...
Peter Clifton schreef/a écrit/wrote in/dans/in
le/on/op 16/02/2004 :

So I presumed a faulty LOPT. This was confirmed by rudimentary ring
testing
on my oscilloscope.

Do LOPTs just fail on their own, or are they usually 'caused' to fail by
another part?

They fail on their own, Peter. Especially in those sets. We replace a
few every week.
The quality of those transformer has dropped dramaticaly.

Sometimes the line output transistor has to be replaced as well and a
little blue capacity, close to that transistor.

Greetz,

--
Alain Beguin http://home.tiscali.be/a.beguin
mailto: http://cerbermail.com/?XiEiqwImaa
MesNews Reader: http://www.zoo-logique.org/mesnews/index-gb.php