Any ideas on this? please.

[Tim]

Hi all,

I am hoping someone here may be able to help me with solving an intermittent
fault with our family TV
It is a Phillips 21PT2012 / 79R and has what I think is the serial number
of BZ000231 723707 on the back cover.
The fault manifests itself as sudden loss of all picture, and light from the
screen and loss of sound at the same time, anywhere from 5 seconds to a few
minutes from switch on.
This started a week or so ago, and a turn off seemed to fix it, and now it
will not run longer than a minute or so without dying. It seems like the HT
supply drops out suddenly,
but as I understand it the power supply rails for all the circuitry on this
type of appliance may very well all come from one switching supply, and a
fault there could wipe out everything?
I have a reasonable understanding of electronics, and a good Fluke
multimeter, but no cct. diagram, and no experience with TVs. Any
suggestions? I think that the set is about 4 years old, and I guess it must
be some component that is built to a commercial standard starting to break
down, but I was hoping that there may be hope rather than junking it?
Thanks for any assistance.

Tim

 

[Jamie]

Hi all,

I am hoping someone here may be able to help me with solving an intermittent
fault with our family TV
It is a Phillips 21PT2012 / 79R and has what I think is the serial number
of BZ000231 723707 on the back cover.
The fault manifests itself as sudden loss of all picture, and light from the
screen and loss of sound at the same time, anywhere from 5 seconds to a few
minutes from switch on.
This started a week or so ago, and a turn off seemed to fix it, and now it
will not run longer than a minute or so without dying. It seems like the HT
supply drops out suddenly,
but as I understand it the power supply rails for all the circuitry on this
type of appliance may very well all come from one switching supply, and a
fault there could wipe out everything?
I have a reasonable understanding of electronics, and a good Fluke
multimeter, but no cct. diagram, and no experience with TVs. Any
suggestions? I think that the set is about 4 years old, and I guess it must
be some component that is built to a commercial standard starting to break
down, but I was hoping that there may be hope rather than junking it?
Thanks for any assistance.

Tim

check for bad solder joints on the board. and also the circuit control
voltage relay which most likely is in the power supply section, that
many times burn the contacts.
if not that, find the regulator on the switching supply, test for
voltage getting to that point. Also, you should take note if the TV
seems to have a short burst of power before it decides not to fire up,
this would indicate a short maybe in the HT section. Normally the Start
up circuit in the switching supply has a short override of the fault
sensing from the HT section so that it makes an attempt to start.

 

[Don Lancaster]

Hi all,

I am hoping someone here may be able to help me with solving an intermittent
fault with our family TV
It is a Phillips 21PT2012 / 79R and has what I think is the serial number
of BZ000231 723707 on the back cover.
The fault manifests itself as sudden loss of all picture, and light from the
screen and loss of sound at the same time, anywhere from 5 seconds to a few
minutes from switch on.
This started a week or so ago, and a turn off seemed to fix it, and now it
will not run longer than a minute or so without dying. It seems like the HT
supply drops out suddenly,
but as I understand it the power supply rails for all the circuitry on this
type of appliance may very well all come from one switching supply, and a
fault there could wipe out everything?
I have a reasonable understanding of electronics, and a good Fluke
multimeter, but no cct. diagram, and no experience with TVs. Any
suggestions? I think that the set is about 4 years old, and I guess it must
be some component that is built to a commercial standard starting to break
down, but I was hoping that there may be hope rather than junking it?
Thanks for any assistance.

Tim

The problem with getting a schematic and monitoring the voltages is...?


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: [email protected]

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Tim]

Don,
Thanks
I would certainly use a schematic if I had one. Would you know if thwere is
an on line source for them, I thought that the manufacturers would be
reluctent to make them available to any other than there representative
service agents?
Tim

 

[Don Lancaster]

Don,
Thanks
I would certainly use a schematic if I had one. Would you know if thwere is
an on line source for them, I thought that the manufacturers would be
reluctent to make them available to any other than there representative
service agents?
Tim

http://www.samswebsite.com/photofacts.html

--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: [email protected]

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Eeyore]

Hi all,

I am hoping someone here may be able to help me with solving an intermittent
fault with our family TV
It is a Phillips 21PT2012 / 79R and has what I think is the serial number
of BZ000231 723707 on the back cover.
The fault manifests itself as sudden loss of all picture, and light from the
screen and loss of sound at the same time, anywhere from 5 seconds to a few
minutes from switch on.
This started a week or so ago, and a turn off seemed to fix it, and now it
will not run longer than a minute or so without dying. It seems like the HT
supply drops out suddenly,
but as I understand it the power supply rails for all the circuitry on this
type of appliance may very well all come from one switching supply, and a
fault there could wipe out everything?
I have a reasonable understanding of electronics, and a good Fluke
multimeter, but no cct. diagram, and no experience with TVs. Any
suggestions? I think that the set is about 4 years old, and I guess it must
be some component that is built to a commercial standard starting to break
down, but I was hoping that there may be hope rather than junking it?
Thanks for any assistance.

Cross-posted to a more suitable group

Graham

 

[[email protected]]

Hi,

I think the problem is with the HT Flashover. Due to this the SMPS
sees a sudden pull of current and switches off everything. In fact iam
working with Philips and Philips Monitors also have similar problems.
Good Luck.

Bhaskar.

 

[Tim]

,
Thanks very much for the lead.
Tim