Samsung TV convergence problems

[97tjMike]

Hello everyone:

I have a samsung projection tv model no: HCN4727W

The convergence is off as it does not let me adjust blue, and while
red adjusts fine, it is warped at the top and bottom. I pulled the
convergence board, and it appears that the two IC units have been
replaced at least once in the TV's lifetime (I just got the tv and
have no idea of its prior history). Also, the repairman soldered pins
1,2, and 3 of both IC units in line with a resistor (or maybe a diode
I'm not sure), and then connected the resistor to the -20v terminal on
the board. I'm not sure why this modification would be necessary, as
it appears the IC chips are OEM (they're both STK392-040). Anyways, I
was thinking of just replacing the entire unit (board and all) and
seeing what happens. Good or bad idea?

http://www.samsungparts.com/part_de...&product_id=BP95-00142P&search_model=HCN4727W

Mike

 

[Meat Plow]

Hello everyone:

I have a samsung projection tv model no: HCN4727W

The convergence is off as it does not let me adjust blue, and while
red adjusts fine, it is warped at the top and bottom. I pulled the
convergence board, and it appears that the two IC units have been
replaced at least once in the TV's lifetime (I just got the tv and
have no idea of its prior history). Also, the repairman soldered pins
1,2, and 3 of both IC units in line with a resistor (or maybe a diode
I'm not sure), and then connected the resistor to the -20v terminal on
the board. I'm not sure why this modification would be necessary, as
it appears the IC chips are OEM (they're both STK392-040). Anyways, I
was thinking of just replacing the entire unit (board and all) and
seeing what happens. Good or bad idea?

Probably a good idea especially if you don't know the difference between a
resistor and a diode.

 

[97tjMike]

Probably a good idea especially if you don't know the difference between a
resistor and a diode.

ah well i know their difference functionality wise, just not
appearance wise. i'd call it a resistor except it has a glossy coating
common to diodes

 

[William Sommerwerck]

ah well i know their difference functionality wise, just not
appearance wise. i'd call it a resistor except it has a glossy
coating common to diodes

I believe the Mr. Plow was not trying to be lightly humorous, but was being
sarcastic at your expense.

 

[Smitty Two]

I believe the Mr. Plow was not trying to be lightly humorous, but was being
sarcastic at your expense.

I believe the Mr. Plow was being neither sarcastic nor humorous, but
merely matter-of-fact. Tis a rare individual who knows the theoretical
difference between a resistor and a diode but cannot properly
distinguish the two. Nevertheless, the OP is clearly unqualified to
troubleshoot to the component level.

 

[AJ]

Cost of the replacment board via Samsung would probably be less investment
than troubleshooting the original pcb. IMHO

 

[JANA]

I have not worked on that model myself. But, most of the time the failures
are the driver IC's, bias resistors and caps. If available, some of the
service techs will replace the complete convergence board.

Considering the age of the set, and the fact that it uses tube technology
for the display, maybe you should consider something up to date and
dependable rather than chase the faults in this one.

--

JANA
_____


Hello everyone:

I have a samsung projection tv model no: HCN4727W

The convergence is off as it does not let me adjust blue, and while
red adjusts fine, it is warped at the top and bottom. I pulled the
convergence board, and it appears that the two IC units have been
replaced at least once in the TV's lifetime (I just got the tv and
have no idea of its prior history). Also, the repairman soldered pins
1,2, and 3 of both IC units in line with a resistor (or maybe a diode
I'm not sure), and then connected the resistor to the -20v terminal on
the board. I'm not sure why this modification would be necessary, as
it appears the IC chips are OEM (they're both STK392-040). Anyways, I
was thinking of just replacing the entire unit (board and all) and
seeing what happens. Good or bad idea?

http://www.samsungparts.com/part_de...&product_id=BP95-00142P&search_model=HCN4727W

Mike

 

[97tjMike]

I believe the Mr. Plow was being neither sarcastic nor humorous, but
merely matter-of-fact. Tis a rare individual who knows the theoretical
difference between a resistor and a diode but cannot properly
distinguish the two. Nevertheless, the OP is clearly unqualified to
troubleshoot to the component level.

I wouldn't concern yourself with my lack of expertise so much. I have
and EE friend who I'm working with. Just didn't have a chance to have
him look at the board before I posted this. After having him looking
at the board, we found that they are indeed diodes, and they are
soldered to pins 1-3, which, according to a schematic of the ICs which
we found online, pins 1-3 are not connected to anything. That's why
I'm very curious why someone would put an diode to those terminals.
But anyways we're gonna try to replace the IC units themselves (and
omit the diodes), because from what I've read elsewhere it seems that
the ICs tend to fail frequently.

 

[Meat Plow]

I wouldn't concern yourself with my lack of expertise so much. I have
and EE friend who I'm working with. Just didn't have a chance to have
him look at the board before I posted this. After having him looking
at the board, we found that they are indeed diodes, and they are
soldered to pins 1-3, which, according to a schematic of the ICs which
we found online, pins 1-3 are not connected to anything. That's why
I'm very curious why someone would put an diode to those terminals.
But anyways we're gonna try to replace the IC units themselves (and
omit the diodes), because from what I've read elsewhere it seems that
the ICs tend to fail frequently.

If they are serviced correctly, those devices shouldn't fail frequently.
I found that on my 2000 Panasonic 53" TV they failed earlier this year
because the mounting screws were not tight. I don't know if they were not
tight from the factory or somehow from heat cool cycles managed to loosen
on their own. Regardless if properly installed and there are no other
hidden problems, the repeat failure rate should be fairly low. Remember to
use original factory parts and not OEM. Those devices are probably the
hardest working electronics in the entire set.

 

[97tjMike]

If they are serviced correctly, those devices shouldn't fail frequently.
I found that on my 2000 Panasonic 53" TV they failed earlier this year
because the mounting screws were not tight. I don't know if they were not
tight from the factory or somehow from heat cool cycles managed to loosen
on their own. Regardless if properly installed and there are no other
hidden problems, the repeat failure rate should be fairly low. Remember to
use original factory parts and not OEM. Those devices are probably the
hardest working electronics in the entire set.

here's a followup:

we replaced the two IC chips in the board, and,while the colors seem
to be more well definied, the blue convergence still will not adjust.
We were able to adjust the focus on the picture tube, so focus is no
longer an issue. However, the convergence problem still occurs. Should
we replace the 1st convergence board (not the one with the IC chips.)?
Just looking for reccomendations. Thanks
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&Item=320175796310&Category=61407&_trksid=p3907.m29

 

[Mark D. Zacharias]

here's a followup:

we replaced the two IC chips in the board, and,while the colors seem
to be more well definied, the blue convergence still will not adjust.
We were able to adjust the focus on the picture tube, so focus is no
longer an issue. However, the convergence problem still occurs. Should
we replace the 1st convergence board (not the one with the IC chips.)?
Just looking for reccomendations. Thanks
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&Item=320175796310&Category=61407&_trksid=p3907.m29

Sometimes there are fuses (pico-fuses) or resistors associated with the
STK's which are bad also...

Mark Z.

 

[Meat Plow]

Sometimes there are fuses (pico-fuses) or resistors associated with the
STK's which are bad also...

Mark Z.

I agree with Mark. Look for some low value 10 ohm, small wattage (1/10
watt) near the place on the board where the yoke leads are soldered into
it. Given that you are not the first to service this set and the fact that
the previous tech did some modifications, I would take an educated guess
that there is still trouble on the IC board. Note, you'll pretty much have
to shotgun the other components near the STK chips. Pay attention to those
that have the same grid location as the STK chips, example: IC9001,
R9001,R9002 etc...