[TechAssist] FIXED Samsung TXJ2767 K51A chassis dead

  • From: Jorge Camboni <geo@xxxxxxxxxxxxx>
  • To: techassist@xxxxxxxxxxxxx
  • Date: Thu, 19 Feb 2004 16:59:01 -0600

Well,  b4 giving up, I ordered T801, the switching transformer.
It took ages to arrive (Samsungparts had it on back order)
but I finally got hold of it today, I soldered it in place, et voil=E0!!!!!!
IT WORKED!
So it was T801 after all
Thanks for all  the advice on this problem. I feel a little
bit older and my hair is a little more scarce (if possible)
after all I ran in circles biting my tail with this set.
You all have fun, if possible
Jorge
PS Actually it's a 32" set and I don't remember the model
(I only brought the mainboard)
but chassis is the K51A, identical to the model I posted

**************************************************
On the 06/02/04 , Jorge Camboni, GY Electronics, Richardson, TX
(MYSELF) wrote this desperate message in a bottle:

" I am about to give up with this. It's a Samsung K51A chassis
and the main power uspply is giving 10 volts to the HOT collector and
the rest of the voltages are low by the same proportion..

It uses a 3S1265H as the switching regulator and I already tried
2 different new replacements with no luck (actually, the schematic shows
a 3S1265R and I tried a R and a RF -it makes no difference, the RD is
totally isolated, the R has a metallic tab-)
I measured component by component, the diodes, caps, ICs and resistors
are all ok, there is nothing overloading the secondary - cold side of the=
 power
supply, I actually disconnected branch by branch and nothing changed.
Besides the secondary voltages which are dramatically lowered to a mere 10%,
the voltages at the IC are the following: pin 1) has the correct voltage,=20
sometimes
reading higher because it is oscillating somehow. pin 3) -VCC- has between=
=20
11 and 13 volts,
never reaches 17V as the schematics shows;  voltage goes up and down all=20
the time.
pin 4) has nothing, schematic shows .9V,   Pin 5 has nothing or a few mv,=20
though schematic
says 8.2V  that is the sync/feedback pin, it is connected to T801, maybe=20
here applies
the less-than-10% rule, as with the other windings.
Besides that, if place a 60 watt bulb as a load on the 130v (leaving the=20
HOT collector floating
first), the voltage goes still lower, down to maybe 3 volts or so.=20
Conversely if you leave
all the secondaries floating, the 130 volts raise to nearly 70, but goes=20
immediately down
with any light load you place on it or on the other low voltage rectifiers.

I'm about to give up. The only unchecked/unchanged component is T801, but=20
it CAN'T be...
Any help will be greatly appreciated

TIA
Jorge"

Jorge Camboni, GY Electronics, Richardson, TX =20


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