Philips oldtimer: 20 year old tv set died
 

My old (20 years) faithful Philips TV-set died last day, and I have tried to
find the cause, without success. As far as I know, I think it is in the
startup circuits.

What do I know?

-Chassis: 26CS5779/13Z
-Death: Just died while watching
-Fuses: checked OK

Symptoms:

-No high tension.
-Faint hiss in speaker
-Responds to remote control but channel indicator dead.
-13V and 190V test points on board have no voltage.
-140V collector-emitter voltage on flyback transistor. No base voltage.
Unsoldered and checked OK.
-Most transistors tested by using diode test. 0.7v drop. =ok
-Diodes checked OK.

Any clues as where to look?
thanks a bunch!

Andy

If you put a scope on the base of the HOT, do you get the startup pulse
train? If so, this means that the kick start for the scans and power supply
should normally be okay.

There is a chance that there is a scan or HV fault, and it is going in to
the protect mode. In many sets, when they do this type of fault, I have
found them to have defective capacitors, and or a defective flyback
transformer. It is also possible at the same time to have some other failed
components as well.

--

Jerry G.
=====

"Andy" wrote in message
...
My old (20 years) faithful Philips TV-set died last day, and I have tried to
find the cause, without success. As far as I know, I think it is in the
startup circuits.

What do I know?

-Chassis: 26CS5779/13Z
-Death: Just died while watching
-Fuses: checked OK

Symptoms:

-No high tension.
-Faint hiss in speaker
-Responds to remote control but channel indicator dead.
-13V and 190V test points on board have no voltage.
-140V collector-emitter voltage on flyback transistor. No base voltage.
Unsoldered and checked OK.
-Most transistors tested by using diode test. 0.7v drop. =ok
-Diodes checked OK.

Any clues as where to look?
thanks a bunch!

Andy

Thank you for your time, Jerry.

I will hook up the scope tomorrow and let you know the result.

Andy

"Jerry G." skrev i meddelandet
...
If you put a scope on the base of the HOT, do you get the startup pulse
train? If so, this means that the kick start for the scans and power
supply
should normally be okay.

There is a chance that there is a scan or HV fault, and it is going in to
the protect mode. In many sets, when they do this type of fault, I have
found them to have defective capacitors, and or a defective flyback
transformer. It is also possible at the same time to have some other
failed
components as well.

--

Jerry G.
=====

"Andy" wrote in message
...
My old (20 years) faithful Philips TV-set died last day, and I have tried
to
find the cause, without success. As far as I know, I think it is in the
startup circuits.

What do I know?

-Chassis: 26CS5779/13Z
-Death: Just died while watching
-Fuses: checked OK

Symptoms:

-No high tension.
-Faint hiss in speaker
-Responds to remote control but channel indicator dead.
-13V and 190V test points on board have no voltage.
-140V collector-emitter voltage on flyback transistor. No base voltage.
Unsoldered and checked OK.
-Most transistors tested by using diode test. 0.7v drop. =ok
-Diodes checked OK.

Any clues as where to look?
thanks a bunch!

Andy

I repaired a Philips set like that last year (K40 chassis) with those
symptoms. It was dry joints near the line transformer - given the age
of the set and the heat generated in use and hence heating- cooling
cyles, that was not a surprise! My tip? resolder EVERYWHERE before
undertaking expensive component swapping.

If not, ....Could be an open resistor in the deflection area.
check the modules on the chassis, remove and reinsert them.

In another K40 set I worked on, There was a red or brown wire from the
power supply to a module on the mainboard which had broken internally -
set was stuck in standby with hiss. I suggest you check all cables like
that with a multimeter

good luck, Ben

Andy wrote:
My old (20 years) faithful Philips TV-set died last day, and I have tried to
find the cause, without success. As far as I know, I think it is in the
startup circuits.
What do I know?
-Chassis: 26CS5779/13Z
-Death: Just died while watching
-Fuses: checked OK
Symptoms:
-No high tension.
-Faint hiss in speaker
-Responds to remote control but channel indicator dead.
-13V and 190V test points on board have no voltage.
-140V collector-emitter voltage on flyback transistor. No base voltage.
Unsoldered and checked OK.
-Most transistors tested by using diode test. 0.7v drop. =ok
-Diodes checked OK.

Apart from broken solder connections on the deflection board and power
supply (which should be fixed, regardless of the symptoms), your TDA3576
line oscillator may have died.

---
Met vriendelijke groet,

Maarten Bakker.

Now, I have hooked up the scope to the base of the scope and found no pulse
train on startup exept one transient burst that seems like startup noise.
However, on shutdown there is a square wave for a fraction of a second. This
is accompanied with a sharp "click" in the speaker and discharge "tweet"
from the power supply area. To be more precise, that "tweet" is actually a
frequency sweep starting at around 1 kHz and increasing.

Martin Bakker suggested that it could be the TDA3576 that has broken. I will
start searching for a datasheet for that device. Or does anybody know on
which pin the output is?

Thanks a lot for your help!

Andy

"Andy" skrev i meddelandet
...
Thank you for your time, Jerry.

I will hook up the scope tomorrow and let you know the result.

Andy

"Jerry G." skrev i meddelandet
...
If you put a scope on the base of the HOT, do you get the startup pulse
train? If so, this means that the kick start for the scans and power
supply
should normally be okay.

There is a chance that there is a scan or HV fault, and it is going in to
the protect mode. In many sets, when they do this type of fault, I have
found them to have defective capacitors, and or a defective flyback
transformer. It is also possible at the same time to have some other
failed
components as well.

--

Jerry G.
=====

"Andy" wrote in message
...
My old (20 years) faithful Philips TV-set died last day, and I have tried
to
find the cause, without success. As far as I know, I think it is in the
startup circuits.

What do I know?

-Chassis: 26CS5779/13Z
-Death: Just died while watching
-Fuses: checked OK

Symptoms:

-No high tension.
-Faint hiss in speaker
-Responds to remote control but channel indicator dead.
-13V and 190V test points on board have no voltage.
-140V collector-emitter voltage on flyback transistor. No base voltage.
Unsoldered and checked OK.
-Most transistors tested by using diode test. 0.7v drop. =ok
-Diodes checked OK.

Any clues as where to look?
thanks a bunch!

Andy

Sorry, got Maarten's name wrong. My apologies!

"Andy" skrev i meddelandet
...
Now, I have hooked up the scope to the base of the scope and found no
pulse train on startup exept one transient burst that seems like startup
noise. However, on shutdown there is a square wave for a fraction of a
second. This is accompanied with a sharp "click" in the speaker and
discharge "tweet" from the power supply area. To be more precise, that
"tweet" is actually a frequency sweep starting at around 1 kHz and
increasing.

Martin Bakker suggested that it could be the TDA3576 that has broken. I
will start searching for a datasheet for that device. Or does anybody know
on which pin the output is?

Thanks a lot for your help!

Andy

"Andy" skrev i meddelandet
...
Thank you for your time, Jerry.

I will hook up the scope tomorrow and let you know the result.

Andy

"Jerry G." skrev i meddelandet
...
If you put a scope on the base of the HOT, do you get the startup pulse
train? If so, this means that the kick start for the scans and power
supply
should normally be okay.

There is a chance that there is a scan or HV fault, and it is going in
to
the protect mode. In many sets, when they do this type of fault, I have
found them to have defective capacitors, and or a defective flyback
transformer. It is also possible at the same time to have some other
failed
components as well.

--

Jerry G.
=====

"Andy" wrote in message
...
My old (20 years) faithful Philips TV-set died last day, and I have
tried to
find the cause, without success. As far as I know, I think it is in the
startup circuits.

What do I know?

-Chassis: 26CS5779/13Z
-Death: Just died while watching
-Fuses: checked OK

Symptoms:

-No high tension.
-Faint hiss in speaker
-Responds to remote control but channel indicator dead.
-13V and 190V test points on board have no voltage.
-140V collector-emitter voltage on flyback transistor. No base voltage.
Unsoldered and checked OK.
-Most transistors tested by using diode test. 0.7v drop. =ok
-Diodes checked OK.

Any clues as where to look?
thanks a bunch!

Andy