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Old 1st January 2009, 02:27 PM   #1
diyAudio Member
Join Date: Oct 2007
Default SMPS Trouble, wont start - need some advice! Full schematic

I have a SMPS wich is normally fitted into a Pioneer plasma screen. The SMPS is on a separate PCB and made by hitachi.

The first thing i replaced was R133 wich was open due to high
current when Q125 shorted. Both Q125 and R133 are replaced
Q125(2sk2651) R133 = 0.1ohm Brown Black Silver Gold.

I also replaced Q126 with a similar device.
Q119 wich is the "driver" did not have any reading when measured out of circuit so i replaced this one also.

The problem is that i only have the 5V Standby Voltage wich is
fed directly before rectification.

It just wont start up, no smoke no nothing. The "ALARM" LED is
lit as soon as i plugg in the power cable. I dont know what that
means but i guess something is wrong. R362 gets quite hot but
it is a high wattage resistor.

One problen that i can se is that Q109 wont turn on, i just get a
over and over from 0v to 0.45v cycle on the base.

I really need some advice, today i took voltage readings on nearly ALL ICs.

Schematic here, page 129 and 131.
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