DAMN i feel like i been to hell and back with this thing! i finally
found a nice guy at a TV repair shop who was willing to give me some
functional information, but he told me that the cost was $90 just to put
my SMPS on the bench and tell me which components were bad.
after surfing to the far corners of cyberspace, my only option is to
repair the thing myself.
if people could give me some tips it would really save what is left of
my ass.
so here's the deal:

-switch mode, looks like a half bridge type unit, form a projection TV

-customer did some electrical work and sent 220 volts up the cord, now
when i plug it in the only sign of life is a periodical, barely audible,
click like a microscopic spark discharge.

-but i know that's not what it is, because the outputs on the supply are
totally flat. in circuit completely plugged in. dead. 0 volts ac & dc

-the source voltage, raw 110, full rectified, filtered, is fine.
measured approx 180 steady DC, which

-goes to a STK730-130 regulator and support circuitry.

-take it out of circuit. check it out: no visible signs of damage
anywhere. no fuses.

from left to right: input section, 180 DC, checks out

mid section, STK chip, other circuitry, 5 primary taps. here i see
something, i don't get it.

theres a single resistor connected to STK pin 5. that's the "TR1 gate"
pin. it must be the start resistor, but no, the other end of the
resistor goes to DC ground, so it can't be.....whatever, the point is,
its measuring only 8 ohms even though its supposed to be
(hmmmmm....1....0.....yellow. 5?....4!) uuuuuhh.....100k. but am i just
measuring the resistor? maybe the STK is shorted inside. who knows where
those electrons are off to?

here's something else, while it was in circuit i found the STK ground
pin and found that there wasn't any voltage present on any of the other
pins, ac or dc, except pin 11, the "TR1 drain" pin. 180 volts on pin 11.
so the transistor must be shorted. i guess.

right section, isolated by the transformer and a photocoupler, looks OK,
diodes are OK, but how do you test a cap in circuit? or the transformer?

and how do you trick it into thinking its in circuit so i can measure
the outputs? its a projection TV, but i got no specs on voltage or
wattage. and i can't get a doc for the STK730-130.

you EE guys must have some fancy tricks n stuff to do this work.

thanks anyone just for reading this message. hope someone can help.

Louie

Louie wrote in
news:WRz_a.137822$o%2.59125@sccrnsc02:

DAMN i feel like i been to hell and back with this thing! i finally
found a nice guy at a TV repair shop who was willing to give me some
functional information, but he told me that the cost was $90 just to put
my SMPS on the bench and tell me which components were bad.
after surfing to the far corners of cyberspace, my only option is to
repair the thing myself.
if people could give me some tips it would really save what is left of
my ass.
so here's the deal:

-switch mode, looks like a half bridge type unit, form a projection TV

-customer did some electrical work and sent 220 volts up the cord, now
when i plug it in the only sign of life is a periodical, barely audible,
click like a microscopic spark discharge.

-but i know that's not what it is, because the outputs on the supply are
totally flat. in circuit completely plugged in. dead. 0 volts ac & dc

-the source voltage, raw 110, full rectified, filtered, is fine.
measured approx 180 steady DC, which

-goes to a STK730-130 regulator and support circuitry.

-take it out of circuit. check it out: no visible signs of damage
anywhere. no fuses.

from left to right: input section, 180 DC, checks out

mid section, STK chip, other circuitry, 5 primary taps. here i see
something, i don't get it.

theres a single resistor connected to STK pin 5. that's the "TR1 gate"
pin. it must be the start resistor, but no, the other end of the
resistor goes to DC ground, so it can't be.....whatever, the point is,
its measuring only 8 ohms even though its supposed to be
(hmmmmm....1....0.....yellow. 5?....4!) uuuuuhh.....100k. but am i just
measuring the resistor? maybe the STK is shorted inside. who knows where
those electrons are off to?

here's something else, while it was in circuit i found the STK ground
pin and found that there wasn't any voltage present on any of the other
pins, ac or dc, except pin 11, the "TR1 drain" pin. 180 volts on pin 11.
so the transistor must be shorted. i guess.

right section, isolated by the transformer and a photocoupler, looks OK,
diodes are OK, but how do you test a cap in circuit? or the transformer?

and how do you trick it into thinking its in circuit so i can measure
the outputs? its a projection TV, but i got no specs on voltage or
wattage. and i can't get a doc for the STK730-130.

you EE guys must have some fancy tricks n stuff to do this work.

thanks anyone just for reading this message. hope someone can help.

Louie


Seems like you could go to the ECG website and find their version of this
STK730 device,and they will have specs and pinout on it.

--
Jim Yanik,NRA member
remove null to contact me

Have you checked the output rectifiers for shorts? the ticking sound you
hear is the transformer as the supply is most likely working in protection
mode, trying to start up registering a fault and resetting, "trip mode" if
the line voltage was too high (220v) I would expect that the chip had failed
I would also look at the reservior cap usually 220uf or so, here in the UK
we use 240v mains so our caps are rated at 350v for mains reservior caps,
but I guess if you only have 110v mains then 200v would be in order, you can
usually take the power unit out and dissconnect the supply that feds the
horizontal HT supply and substitue the load with a 100w fillament lamp, this
will present a working load to the psu, but probably you would do well to
just change stk and the photocoupler ic's as it seems like you are unable to
test any of them

good luck

RID


"Louie" wrote in message
news:WRz_a.137822$o%2.59125@sccrnsc02...
DAMN i feel like i been to hell and back with this thing! i finally
found a nice guy at a TV repair shop who was willing to give me some
functional information, but he told me that the cost was $90 just to put
my SMPS on the bench and tell me which components were bad.
after surfing to the far corners of cyberspace, my only option is to
repair the thing myself.
if people could give me some tips it would really save what is left of
my ass.
so here's the deal:

-switch mode, looks like a half bridge type unit, form a projection TV

-customer did some electrical work and sent 220 volts up the cord, now
when i plug it in the only sign of life is a periodical, barely audible,
click like a microscopic spark discharge.

-but i know that's not what it is, because the outputs on the supply are
totally flat. in circuit completely plugged in. dead. 0 volts ac & dc

-the source voltage, raw 110, full rectified, filtered, is fine.
measured approx 180 steady DC, which

-goes to a STK730-130 regulator and support circuitry.

-take it out of circuit. check it out: no visible signs of damage
anywhere. no fuses.

from left to right: input section, 180 DC, checks out

mid section, STK chip, other circuitry, 5 primary taps. here i see
something, i don't get it.

theres a single resistor connected to STK pin 5. that's the "TR1 gate"
pin. it must be the start resistor, but no, the other end of the
resistor goes to DC ground, so it can't be.....whatever, the point is,
its measuring only 8 ohms even though its supposed to be
(hmmmmm....1....0.....yellow. 5?....4!) uuuuuhh.....100k. but am i just
measuring the resistor? maybe the STK is shorted inside. who knows where
those electrons are off to?

here's something else, while it was in circuit i found the STK ground
pin and found that there wasn't any voltage present on any of the other
pins, ac or dc, except pin 11, the "TR1 drain" pin. 180 volts on pin 11.
so the transistor must be shorted. i guess.

right section, isolated by the transformer and a photocoupler, looks OK,
diodes are OK, but how do you test a cap in circuit? or the transformer?

and how do you trick it into thinking its in circuit so i can measure
the outputs? its a projection TV, but i got no specs on voltage or
wattage. and i can't get a doc for the STK730-130.

you EE guys must have some fancy tricks n stuff to do this work.

thanks anyone just for reading this message. hope someone can help.

Louie

Rid wrote:

Have you checked the output rectifiers for shorts?

all the diodes on the board measre about 7 ohms forward, infinite
reverse.

the ticking sound you
hear is the transformer as the supply is most likely working in protection
mode, trying to start up registering a fault and resetting, "trip mode" if
the line voltage was too high (220v) I would expect that the chip had failed

is that what the "error detection level" pin on the chip is for?

I would also look at the reservior cap usually 220uf or so, here in the UK
we use 240v mains so our caps are rated at 350v for mains reservior caps,
but I guess if you only have 110v mains then 200v would be in order

yeah its rated for 200V but its still working just fine. takes a few
minutes to discharge on its own after i pull the plug.

you can
usually take the power unit out and dissconnect the supply that feds the
horizontal HT supply and substitue the load with a 100w fillament lamp, this
will present a working load to the psu, but probably you would do well to
just change stk and the photocoupler ic's as it seems like you are unable to
test any of them

that's what i intend to do. thanks, RID
Louie