Goldstar 1468 (Chassis CA-32) - SMPS problem

[mikippp@poczta.onet.pl]

I am trying to repair a Goldstar 1468 SMPS. It is dated Aug. 1995,
Chassis CA-32.

I am now checking the power supply section which uses a
STRS5717 and a multi-output transformer.
The STRS5717 is a 9 pin(zig-zag pins) I.C. which drives the
primary of a transformer to generate secondary outputs of
125v, 95v(B+), 65v, 40v, 12v and 6.3v. All these outputs are
rectified with diodes and electrolytic caps before being fed
to the circuits they drive.
The rectified outputs of 40v, 12v, 6.3v are all low (about half the
espected value). The 12v reads about 6v (d.c) so all the ICs
mentioned below are not active/working correctly.
The HOT tested good. ESR on of the Electrolytic caps. tested good.

--
Thanks Miki

 

[Bledge]

In article <7384971b.0310170217.142a33d2@posting.google.com>,
mikippp@poczta.onet.pl (mikippp@poczta.onet.pl) wrote:

I am trying to repair a Goldstar 1468 SMPS. It is dated Aug. 1995,
Chassis CA-32.

There was a CA-32/LG1505s schematic from

http://rv6llh.rsuh.ru/shema.htm filename= GS_1505.zip

It is probably still there

I am now checking the power supply section which uses a
STRS5717 and a multi-output transformer.
The STRS5717 is a 9 pin(zig-zag pins) I.C. which drives the
primary of a transformer to generate secondary outputs of
125v, 95v(B+), 65v, 40v, 12v and 6.3v. All these outputs are
rectified with diodes and electrolytic caps before being fed
to the circuits they drive.
The rectified outputs of 40v, 12v, 6.3v are all low (about half the
espected value). The 12v reads about 6v (d.c) so all the ICs
mentioned below are not active/working correctly.

Had the same problem on a CA-32/LG1505s.
There was a shorted transistor Q905/2SA1837 on the +125v
on the secondary side of the smps transformer.
On the CA32/LG1505s schematic, trace pin9 on the secondary of
the smps tranformer and you will see Q905 after the +125v rectifier.

This fixed the 40v, 12v, 6.3v being about half the expected value
in my case. However you will need to find other bad components in
other parts of the circuit which caused the Q905 to short.

Use the series light bulb trick in Sam's Monitor FAQ to prevent
blown components while troubleshooting.

The HOT tested good. ESR on of the Electrolytic caps. tested good.

HOT was good but I had 2 burnt resistors and a shorted
1uF/63v cap on the ABL circuit and
"Bill Jr" replied: "Any time I've seen the ABL resistor burnt the flyback
was bad, no matter how it did on a ring test. "

/bledge 21 Oct 2003