PC Shorted Tube Yoke Transistor help

R

Ren

Guest
Hi there..

I have a Pc monitor in peices that failed on me.
I have tracked the problem down to a shorted Transistor that feeds the Yoke
Coil around the Neck of the Tube. (Possibly Horizontal Deflection ? )
Can someone give me a general run down on what usually causes this to fail .
I have checked all surrounding Diodes and all seem ok.
The Minitor that i have removed the Transistor from is a
17" Digital PCXAV-YY
The Transistor that is shorted is a 2SC5331 .
Could i replace this with a 2SC5411 ?

Cheers


Ren(NZ)
 
Data sheet for 2SC5331 http://wwww.ges.cz/sheet/2/2sc5331.pdf
Ditto for 2SC5411 http://rv6llh.rsuh.ru/PDF/2SC/2SC5411.pdf

While the pin spacing is similar the major difference is the package
size and power rating. The 5331 is rated at 180W while the 5411 is only 60W.

I would guess that the designers knew what they were doing in specifying
the 5331 for your monitor. On that basis then the answer has to be no,
the 5411 will not be a suitable replacement for the 5331 in your set.
The 2SC3996 http://www.datadart.com/al/sanyo/2SC3996.pdf would be ok but
that is even more expensive than the 5331. WES in Sydney quote $16 for
the 5331 and $23.50 for the 3996.

Rgds,

Ross H

Ren wrote:
Hi there..

I have a Pc monitor in peices that failed on me.
I have tracked the problem down to a shorted Transistor that feeds the Yoke
Coil around the Neck of the Tube. (Possibly Horizontal Deflection ? )
Can someone give me a general run down on what usually causes this to fail .
I have checked all surrounding Diodes and all seem ok.
The Minitor that i have removed the Transistor from is a
17" Digital PCXAV-YY
The Transistor that is shorted is a 2SC5331 .
Could i replace this with a 2SC5411 ?

Cheers


Ren(NZ)
Click to expand...
 
Thanks Ross..

Your Dead right.
Just after i made the posting i managed to find a cross referance to the
2SC3996 Which does match to the 2SC5331.
Do you know what genarally takes these out or makes them short circuit.
The only thing in circuit is the coils around the Neck of the Tube, as far
as i can see..

Or do these Transistors just break down over time ?


"Ross Herbert" <rherber1@bigpond.net.au> wrote in message
news:6Qa9b.102720$bo1.15609@news-server.bigpond.net.au...
Data sheet for 2SC5331 http://wwww.ges.cz/sheet/2/2sc5331.pdf
Ditto for 2SC5411 http://rv6llh.rsuh.ru/PDF/2SC/2SC5411.pdf

While the pin spacing is similar the major difference is the package
size and power rating. The 5331 is rated at 180W while the 5411 is only
60W.

I would guess that the designers knew what they were doing in specifying
the 5331 for your monitor. On that basis then the answer has to be no,
the 5411 will not be a suitable replacement for the 5331 in your set.
The 2SC3996 http://www.datadart.com/al/sanyo/2SC3996.pdf would be ok but
that is even more expensive than the 5331. WES in Sydney quote $16 for
the 5331 and $23.50 for the 3996.

Rgds,

Ross H

Ren wrote:
Hi there..

I have a Pc monitor in peices that failed on me.
I have tracked the problem down to a shorted Transistor that feeds the
Yoke
Coil around the Neck of the Tube. (Possibly Horizontal Deflection ? )
Can someone give me a general run down on what usually causes this to
fail .
I have checked all surrounding Diodes and all seem ok.
The Minitor that i have removed the Transistor from is a
17" Digital PCXAV-YY
The Transistor that is shorted is a 2SC5331 .
Could i replace this with a 2SC5411 ?

Cheers


Ren(NZ)
Click to expand...
 
Ren wrote:

Thanks Ross..

Your Dead right.
Just after i made the posting i managed to find a cross referance to the
2SC3996 Which does match to the 2SC5331.
Do you know what genarally takes these out or makes them short circuit.
The only thing in circuit is the coils around the Neck of the Tube, as far
as i can see..

Or do these Transistors just break down over time ?
Click to expand...
These devices are pretty hefty with high voltage and current ratings so
provided they are properly heatsinked the usual cause of breakdown is
excessive current due to low insulation/shorts in the yoke or some
associated component. Without a schematic I couldn't guess what might
have caused yours to fail but unless you can determine what caused it to
go you could find that the replacement device will go the same way at
switch-on. Can be an expensive exercise.....
 
Hi there,

About 2 years ago, I replaced the horizontal output transistor, along
with some diodes and resistors designed to prevent fires when the
transistor shorts, in my mom's TV. Talking to the Sanyo repair guy
when picking up the "genuine replacement parts", he commented: "We see
those transistors fail a lot. Too much heat there. If you can add
additional heatsinking, they will last a lot longer."

I checked it out and sure enough, the transistor and its heat sink was
very hot under normal operating conditions. I replaced the heat sink
with a much larger device from my junk box as well as used good
thermal joint compound mounting the transistor and it now runs at less
than half the original temperature.

Its now 2 1/2 years later and she is still watching the TV.

Cheers from Canada

Bob Morgoch


"Ren" <Renoneninesevenfour@xtra.co.nz> wrote in message news:<_dc9b.148087$JA5.3609978@news.xtra.co.nz>...
Thanks Ross..

Your Dead right.
Just after i made the posting i managed to find a cross referance to the
2SC3996 Which does match to the 2SC5331.
Do you know what genarally takes these out or makes them short circuit.
The only thing in circuit is the coils around the Neck of the Tube, as far
as i can see..

Or do these Transistors just break down over time ?


"Ross Herbert" <rherber1@bigpond.net.au> wrote in message
news:6Qa9b.102720$bo1.15609@news-server.bigpond.net.au...
Data sheet for 2SC5331 http://wwww.ges.cz/sheet/2/2sc5331.pdf
Ditto for 2SC5411 http://rv6llh.rsuh.ru/PDF/2SC/2SC5411.pdf

While the pin spacing is similar the major difference is the package
size and power rating. The 5331 is rated at 180W while the 5411 is only
60W.

I would guess that the designers knew what they were doing in specifying
the 5331 for your monitor. On that basis then the answer has to be no,
the 5411 will not be a suitable replacement for the 5331 in your set.
The 2SC3996 http://www.datadart.com/al/sanyo/2SC3996.pdf would be ok but
that is even more expensive than the 5331. WES in Sydney quote $16 for
the 5331 and $23.50 for the 3996.

Rgds,

Ross H

Ren wrote:
Hi there..

I have a Pc monitor in peices that failed on me.
I have tracked the problem down to a shorted Transistor that feeds the
Yoke
Coil around the Neck of the Tube. (Possibly Horizontal Deflection ? )
Can someone give me a general run down on what usually causes this to
fail .
I have checked all surrounding Diodes and all seem ok.
The Minitor that i have removed the Transistor from is a
17" Digital PCXAV-YY
The Transistor that is shorted is a 2SC5331 .
Could i replace this with a 2SC5411 ?

Cheers


Ren(NZ)
Click to expand...
 
On Mon, 15 Sep 2003 14:15:14 +1200, "Ren"
<Renoneninesevenfour@xtra.co.nz> put finger to keyboard and composed:

I have a Pc monitor in peices that failed on me.
I have tracked the problem down to a shorted Transistor that feeds the Yoke
Coil around the Neck of the Tube. (Possibly Horizontal Deflection ? )
Click to expand...
Yes, it's the horizontal output transistor (HOT).

Can someone give me a general run down on what usually causes this to fail .
I have checked all surrounding Diodes and all seem ok.
Click to expand...
Check the B+ rail with a 240V 100W lamp load with this transistor out
of circuit. If it is too high, then replace any small electrolytic
caps on the primary side of the power supply. Other faults could be
the tuning capacitor (~1600V, usually located between collector and
emitter), the flyback transformer, or the yoke itself (rare). After
replacing the HOT, check that it does not run hot. If it does, then
troubleshoot its base drive. In particular, check any electros around
the line drive transformer that feeds the base.

More complete info is available from the Monitor/TV Repair FAQs.

See http://www.repairfaq.org/REPAIR/F_Repair.html


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
 
On 15 Sep 2003 05:33:30 -0700, bmorgoch@sympatico.ca (Bob M) put
finger to keyboard and composed:

About 2 years ago, I replaced the horizontal output transistor, along
with some diodes and resistors designed to prevent fires when the
transistor shorts, in my mom's TV. Talking to the Sanyo repair guy
when picking up the "genuine replacement parts", he commented: "We see
those transistors fail a lot. Too much heat there. If you can add
additional heatsinking, they will last a lot longer."

I checked it out and sure enough, the transistor and its heat sink was
very hot under normal operating conditions. I replaced the heat sink
with a much larger device from my junk box as well as used good
thermal joint compound mounting the transistor and it now runs at less
than half the original temperature.
Click to expand...
I don't understand why any switching transistor should get too hot
under normal operating conditions, unless there is something wrong
with its base drive. AFAIK, the current in the line stage is only
about 1A or so.

See this discussion:
http://www.repairfaq.org/sam/deflfaq.htm#dshot

Why Do Apparently Similar or Better HOTs Sometimes Run Hot:
http://www.repairfaq.org/sam/deflfaq.htm#dsasb

Typical HOT Dissipation:
http://www.repairfaq.org/sam/deflfaq.htm#dsthd

Here is an excerpt from the aforementioned URL:

===============================================================
Here are some measured values for TV HOTs with optimized drive:
(From: David, a Philips application engineer).

14-21", 16 kHz: About 1 W (some have the HOT running in free-air)
21-36", 16 kHz: Less than 2 W (some new large CRT's only need 9 A
p-p)
25-36", 32 kHz: Less than 4 W (dissipation really is prop. to
frequency)
===============================================================


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
 
There's also a fairly useful Yahoo group covering TV and monitor
repairs

http://groups.yahoo.com/group/TVmonitor_schematic_tips

I had an Acer monitor die in July and posted a help request there.
Within 48 hours I had received a full schematic by email, and one UK
service tech had advised the detailed fix:

"Replace Cxxx (2kV) with 3kV and check Qxxx (HOT) for short as a
result of cap failure"

Pulled HOT and sure enough shorted E-C, replace both ex WES and
monitor is now back in service.

If the O/P has a little time on his hands, worth a try
 
Brilliant Budgie.

Thanks for the Site.
Ive been there and searched it out and are a bit more familair with whats
going on now..

Cheers..


Ren
 
Thanks for the help everyone..
Monitor is now back running as smooth as ever.
I ended up repairing a few Dry joins around the Hot area. aswell as
replacing the Horizontal Deflection Transistor.


Cheers

Ren
"Ren" <Renoneninesevenfour@xtra.co.nz> wrote in message
news:UBw9b.149099$JA5.3635665@news.xtra.co.nz...
Brilliant Budgie.

Thanks for the Site.
Ive been there and searched it out and are a bit more familair with whats
going on now..

Cheers..


Ren
Click to expand...
 
Hi..

Any dry joints in the HOT / H.Defl / FBT area will usually result in a dead
HOT - the arcing causes all manner of spikes, rubbish and wierdo waveforms
which blow these already hard working devices sky high.


"Ren" <Renoneninesevenfour@xtra.co.nz> wrote in message
news:XQP9b.150075$JA5.3664717@news.xtra.co.nz...
Thanks for the help everyone..
Monitor is now back running as smooth as ever.
I ended up repairing a few Dry joins around the Hot area. aswell as
replacing the Horizontal Deflection Transistor.


Cheers

Ren
"Ren" <Renoneninesevenfour@xtra.co.nz> wrote in message
news:UBw9b.149099$JA5.3635665@news.xtra.co.nz...
Brilliant Budgie.

Thanks for the Site.
Ive been there and searched it out and are a bit more familair with
whats
going on now..

Cheers..


Ren
Click to expand...
 
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