28PW9623 Philips LED Flashing update

[simon hanlon]

I replaced the bad 220Pf 2kv Cap and the IRF620 series Switch and now the
LED is no longer flashing but there is still no picture or sound. I can hear
a chirping noise I think is coming from the power supply section. Before I
replaced the IRF620 I was getting HV for a couple of seconds, Now there is
no HV just chirping. Any ideas where to look next.
Thanks

 

[simon hanlon]

Haha I fixed it! The replacement IRF720 was not an insulated package and was
shorting on the heatsink now it has a film between and is working fine!!

 

[kip]

OBoy !!

 

[Alain Beguin]

Haha I fixed it! The replacement IRF720 was not an insulated package and was
shorting on the heatsink now it has a film between and is working fine!!

I forgot to mention that some versions are not insulated, sorry for
that and...congratulations ;-)

 

[simon hanlon]

You must be a Jedi! So using the force can you tell me why my KV-28WS2U SONY
takes so long to switch the picture on, its not always but sometimes it
takes a good minute. You can hear the sound but no picture. usually
switching off then back on sorts it. It has always taken some seconds for
the picture but not that long.

 

[Alain Beguin]

You must be a Jedi!

Not at all, only a retired service technician with /some/ experience
with European Philips ;-)

So using the force can you tell me why my KV-28WS2U SONY
takes so long to switch the picture on, its not always but sometimes it takes
a good minute. You can hear the sound but no picture. usually switching off
then back on sorts it. It has always taken some seconds for the picture but
not that long.

Sorry, I can't, because I have *no* experience with Sony

I'm sure someone here will help you!

Bye, Simon.

Alain (Albé)

 

[[email protected]]

Check the voltage on the heater pins of
the picture tube. The electrolytic capacitor in the heater circuit is
probably weak and needs replacing. You should have about 6.3 volts.
John

 

[Andy Cuffe]

Check the voltage on the heater pins of
the picture tube. The electrolytic capacitor in the heater circuit is
probably weak and needs replacing. You should have about 6.3 volts.
John

There's a chance the heater voltage might be less. I know many of
their more recent computer monitors used a 4 or 5 volt heater. I'm
not sure if they did the same thing to their TV CRTs.
Andy Cuffe

[email protected] <-- Use this address until 12/31/2005

[email protected] <-- Use this address after 12/31/2005

 

[simon hanlon]

Great I will take a look and post the results. Thanks

 

[Bram Stolk]

Alain, There I was, having one of these PHILIPS contruptions labelled
28PW9503/12 and showing identical diagnostics as mentioned in this user
group thread. I.e RED LED and Flashing GREEN at power ON.

A visual learned that cap 220PF 2KV at the LOPT area was exploded and really
showed an Ohmic short of about 200 Ohms. Easy does it, get the motherboard
out and Rand R the faulty cap by a 3KV type. Checked the LOPT and it
measured OK.
Get all the connectors back in place and reapplied main power.......Guess
what ..it still did not work ....!!!

I had the chassis shoved under the bench for a few days until I learned
about the message from Alain Beguin the retired Philips Service Engineer
that the FET IRF620 will be the culprit. Not understanding the reasoning
behind it I took the shotgun approach and RandR-ed the FET by an IRF830
giving the machine something to burn out if another short was still
present.(Yes I did insert an ceramic insulator between the FET casing and
the heatsink...

Powered the machine on and watched from a safe distance....PRESTO there was
light and sound...

Alain, people like you should be coddled by the sci.electronics.repair user
group members. This wealth of PHILIPS experience from retired engineers
saves the occasional and theoretical trouble shooters many hours (and
money).

Thanks again and keep on doing the good work on those PHILIPS machines
repair suggestions. (Any knowledge on Grundig CUC 7880 or 7890 as well ?,
BTW In my previous life I used to built aircraft, how does that match your
hobbies ? )

TIA
Bram Stolk (NL)

 

[Alain Beguin]

Bram Stolk wrote in <[email protected]>, on
20/07/2005, H. Margareta van Antiochië

Thanks again and keep on doing the good work on those PHILIPS machines repair
suggestions. (Any knowledge on Grundig CUC 7880 or 7890 as well ?, BTW In my
previous life I used to built aircraft, how does that match your hobbies ? )

I flew them...

Thanks for this nice message and I replyed already by mail.
*Not* much experience with Grundig for the last 12 years