Hello all
Problem with above Samsung, the bottom third of the screen is not there.
Replaced the vertical output IC TDA8356, still the same.
The drive signals coming from the TDA8842,pin 46 and 47, only one is there,
the other one is just a dc level.
It is possible that someone was in the service menu and did change the
vertical settings.
Will try to get the original remote, which I do not have.
Anyone know how to come in the service menu and which options to change.
Thank you very much for any reply
Bert.

Highly probable you actually have a fault in the tele rather than someone
dicking with the service menue. Suspect some of the passive components
around the vertical output, the output itself, etc. post the operational
potentials of the ic when in operation.
"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Hello all
Problem with above Samsung, the bottom third of the screen is not there.
Replaced the vertical output IC TDA8356, still the same.
The drive signals coming from the TDA8842,pin 46 and 47, only one is
there,
the other one is just a dc level.
It is possible that someone was in the service menu and did change the
vertical settings.
Will try to get the original remote, which I do not have.
Anyone know how to come in the service menu and which options to change.
Thank you very much for any reply
Bert.

Highly probable you actually have a fault in the tele rather than someone
dicking with the service menue. Suspect some of the passive components
around the vertical output, the output itself, etc. post the operational
potentials of the ic when in operation.
"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Hello all
Problem with above Samsung, the bottom third of the screen is not there.
Replaced the vertical output IC TDA8356, still the same.
The drive signals coming from the TDA8842,pin 46 and 47, only one is
there,
the other one is just a dc level.
It is possible that someone was in the service menu and did change the
vertical settings.
Will try to get the original remote, which I do not have.
Anyone know how to come in the service menu and which options to change.
Thank you very much for any reply
Bert.



Thanks for the reply Art.
Pin 1 of the TDA8356 has got a nice sawtooth.
Pin 2 of the TDA8356 has a dc level of about 4 volt.
The dc lines are clean and the right value according to the datasheet.
The 2 outputs are there, but the positive and negative outputs do have a
flat part when showing on the scope
Did download the datasheet of the TDA8842, the same I do measure on pins 46
and 47.
I do not know if it is possible to adjust the linearity and shift so far
that one of the outputs is only a dc level.
Only problem is the 8842 is quite expensive but it seems I do have to get
one.
Greetings
Bert.

"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Highly probable you actually have a fault in the tele rather than someone
dicking with the service menue. Suspect some of the passive components
around the vertical output, the output itself, etc. post the operational
potentials of the ic when in operation.
"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Hello all
Problem with above Samsung, the bottom third of the screen is not there.
Replaced the vertical output IC TDA8356, still the same.
The drive signals coming from the TDA8842,pin 46 and 47, only one is
there,
the other one is just a dc level.
It is possible that someone was in the service menu and did change the
vertical settings.
Will try to get the original remote, which I do not have.
Anyone know how to come in the service menu and which options to change.
Thank you very much for any reply
Bert.



Thanks for the reply Art.
Pin 1 of the TDA8356 has got a nice sawtooth.
Pin 2 of the TDA8356 has a dc level of about 4 volt.
The dc lines are clean and the right value according to the datasheet.
The 2 outputs are there, but the positive and negative outputs do have a
flat part when showing on the scope
Did download the datasheet of the TDA8842, the same I do measure on pins
46
and 47.
I do not know if it is possible to adjust the linearity and shift so far
that one of the outputs is only a dc level.
Only problem is the 8842 is quite expensive but it seems I do have to get
one.


Firstly, playing Devil's advocate here, you already replaced the chip, why
would another new chip solve anything? How many chips would you buy until
you either give up the job or conclude, correctly, that the fault is
elsewhere? It's possible, though not highly likely, that the replacement was
DOA, but if it is dead, it is more likely that it was killed by fitting it
into a circuit with other faults.

How do you mean the bottom third is not there? Are you saying the picture
has normal proportions, but the bottom is black, or do you mean the bottom
of the picture is squashed and distorted? If it's the former, the fault is
not necessarily in the vertical output circuit. If it's the latter, try
changing electrolytic caps in the vertical output circuit. Given the low
cost of electrolytics, it's not a bad idea to replace them as a matter of
course when replcing the vertical output chip, as bad ones can destroy the
new chip. After all, electrolytics are probably the least reliable
components there are.

One thing is certain, making adjustments to attempt to cure the fault is a
*very* bad idea. You cannot adjust faults out, you have to repair them!
Making adjustments now then finding you have to make a repair afterwards
will make a satisfactory job a real hassle, or worse still, cause more
damage.

Dave

"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Highly probable you actually have a fault in the tele rather than someone
dicking with the service menue. Suspect some of the passive components
around the vertical output, the output itself, etc. post the operational
potentials of the ic when in operation.
"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Hello all
Problem with above Samsung, the bottom third of the screen is not there.
Replaced the vertical output IC TDA8356, still the same.
The drive signals coming from the TDA8842,pin 46 and 47, only one is
there,
the other one is just a dc level.
It is possible that someone was in the service menu and did change the
vertical settings.
Will try to get the original remote, which I do not have.
Anyone know how to come in the service menu and which options to change.
Thank you very much for any reply
Bert.



Thanks for the reply Art.
Pin 1 of the TDA8356 has got a nice sawtooth.
Pin 2 of the TDA8356 has a dc level of about 4 volt.
The dc lines are clean and the right value according to the datasheet.
The 2 outputs are there, but the positive and negative outputs do have a
flat part when showing on the scope
Did download the datasheet of the TDA8842, the same I do measure on pins
46
and 47.
I do not know if it is possible to adjust the linearity and shift so far
that one of the outputs is only a dc level.
Only problem is the 8842 is quite expensive but it seems I do have to get
one.


Firstly, playing Devil's advocate here, you already replaced the chip, why
would another new chip solve anything? How many chips would you buy until
you either give up the job or conclude, correctly, that the fault is
elsewhere? It's possible, though not highly likely, that the replacement was
DOA, but if it is dead, it is more likely that it was killed by fitting it
into a circuit with other faults.

How do you mean the bottom third is not there? Are you saying the picture
has normal proportions, but the bottom is black, or do you mean the bottom
of the picture is squashed and distorted? If it's the former, the fault is
not necessarily in the vertical output circuit. If it's the latter, try
changing electrolytic caps in the vertical output circuit. Given the low
cost of electrolytics, it's not a bad idea to replace them as a matter of
course when replcing the vertical output chip, as bad ones can destroy the
new chip. After all, electrolytics are probably the least reliable
components there are.

One thing is certain, making adjustments to attempt to cure the fault is a
*very* bad idea. You cannot adjust faults out, you have to repair them!
Making adjustments now then finding you have to make a repair afterwards
will make a satisfactory job a real hassle, or worse still, cause more
damage.

Dave

Ok Dave please hold your horses, there is a little mixed up.
The IC I did replace was the TDA8356, the vertical output chip.
It is a dual input and output IC, have a look at the datasheet please, only
caps are on the suply line.
Boost cap has be replaced, very high ESR.
There was fresh solder on the legs, that is why the replacement.
The set was at another place before I got it to repair.
All electrolytic caps around the vertical and jungle IC has been checked for
the right ESR.
The only thing which does not look right is pin 47 of the 8842, just a
straight dc line on the scope, that is all I do get wrong.
DC supply pins on both IC's are close enough and clean of any spikes.
Deflection coils does ring OK, even checked it with a replacement for a few
seconds, do not want screen burn.
That is why my first question was there, is it possible to adjust Lin and
Shift that far so it looks faulty????
Pin 46 has got the right waveform, a nice sawtooth with the flyback pulse on
top of it.
DC levels of both pins the are the same.
On the bottom third of the screen is nothing, the top two thirds are ok,
linearity not far out and shifted a bit upwards when viewing the screen with
a test picture displayed.
It was not my intention to start adjusting everything in the service menu,
to much experience with sets who where like that.
I do not have much experiance with sets who have a srvice menu, that is why
I came over here.
But thanks for the reply Dave D
Bert.

"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...

Ok Dave please hold your horses, there is a little mixed up.
The IC I did replace was the TDA8356, the vertical output chip.

Fair enough, my mistake.

It is a dual input and output IC, have a look at the datasheet please,
only
caps are on the suply line.
Boost cap has be replaced, very high ESR.
There was fresh solder on the legs, that is why the replacement.
The set was at another place before I got it to repair.
All electrolytic caps around the vertical and jungle IC has been checked
for
the right ESR.

The snag is a capacitor can have an excellent ESR reading, especially if
it's a dead short! The only way to reliably rule out caps IMO is
replacement. ESR testing is very useful, but not conclusive. With vertical
linearity issues I'd suspect electrolytics before anything else, especially
the small ones. Caps might show a good ESR reading, but fail when under
working conditions.

Dave

"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...

Ok Dave please hold your horses, there is a little mixed up.
The IC I did replace was the TDA8356, the vertical output chip.

Fair enough, my mistake.

It is a dual input and output IC, have a look at the datasheet please,
only
caps are on the supply line.
Boost cap has be replaced, very high ESR.
There was fresh solder on the legs, that is why the replacement.
The set was at another place before I got it to repair.
All electrolytic caps around the vertical and jungle IC has been checked
for
the right ESR.

The snag is a capacitor can have an excellent ESR reading, especially if
it's a dead short! The only way to reliably rule out caps IMO is
replacement. ESR testing is very useful, but not conclusive. With vertical
linearity issues I'd suspect electrolytics before anything else, especially
the small ones. Caps might show a good ESR reading, but fail when under
working conditions.

Dave

Hello Dave
Will have a look again tomorrow, the funny thing is the one of the dc
coupled inputs from the 8365 is not there, also the output of the of the
8842.
The only thing left is replacing the 8842 and holding thumbs, will report
back.
Also I will change the few caps.
Customer his to decide it is his money.
Bert.

"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...

Ok Dave please hold your horses, there is a little mixed up.
The IC I did replace was the TDA8356, the vertical output chip.

Fair enough, my mistake.

It is a dual input and output IC, have a look at the datasheet
please,
only
caps are on the supply line.
Boost cap has be replaced, very high ESR.
There was fresh solder on the legs, that is why the replacement.
The set was at another place before I got it to repair.
All electrolytic caps around the vertical and jungle IC has been
checked
for
the right ESR.

The snag is a capacitor can have an excellent ESR reading, especially
if
it's a dead short! The only way to reliably rule out caps IMO is
replacement. ESR testing is very useful, but not conclusive. With
vertical
linearity issues I'd suspect electrolytics before anything else,
especially
the small ones. Caps might show a good ESR reading, but fail when
under
working conditions.

Dave

Hello Dave
Will have a look again tomorrow, the funny thing is the one of the dc
coupled inputs from the 8365 is not there, also the output of the of
the
8842.
The only thing left is replacing the 8842 and holding thumbs, will
report
back.
Also I will change the few caps.
Customer his to decide it is his money.
Bert.