[TechAssist] Re: Samsung TXJ2767 K51A chassis dead
- From: "Intrepid Video Support" <support@xxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Fri, 6 Feb 2004 09:56:57 -0500
Jorge,
Maybe this is close, from Tech Repair CD:
Samsung\TXJ2754\Dead set\\\\IC801*IC851*D803*D805*D806\\\\\\\\
Jeff Dougherty
Intrepid Video TV/VCR
263 S Front St
Steelton PA 17113
fax...717-564-4952
www.intrepid-video.com www.tech-repair.net
----- Original Message -----
From: "Jorge Camboni" <geo@xxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, February 06, 2004 6:36 AM
Subject: [TechAssist] Samsung TXJ2767 K51A chassis dead
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,
sometimes
reading higher because it is oscillating somehow. pin 3) -VCC- has between
11 and 13 volts,
never reaches 17V as the schematics shows; voltage goes up and down all
the time.
pin 4) has nothing, schematic shows .9V, Pin 5 has nothing or a few mv,
though schematic
says 8.2V that is the sync/feedback pin, it is connected to T801, maybe
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
HOT collector floating
first), the voltage goes still lower, down to maybe 3 volts or so.
Conversely if you leave
all the secondaries floating, the 130 volts raise to nearly 70, but goes
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
it CAN'T be...
Any help will be greatly appreciated
TIA
Jorge
Jorge Camboni, GY Electronics, Richardson, TX
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