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Old 10-26-2012, 06:16 AM   #1
Zalinar's Avatar
Join Date: Sep 2012
City & State: Castle Rock, CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 10
Default Magnavox Power supply help 37MF321 LCD TV - Constant 24v inverter voltage...

Hi, I am working on a 3138 103 6338.1 power supply.

I have replaced all electrolytics and several other items. I have tested all Diodes and transistors.

The main problem was a shorted mosfet 7062 which I replaced with a 13A W13NK80Z rather than with an 18A W18NK80Z which I have on order.

All of the voltages are what they are supposed to be at.

The issue:

The 24V to the inverters is always on. From my experience, this should be off until 3v is applied to the standby pin 9 on connector 1089. The power supply does turn on when the 3v is applied. You can hear the transistor powering up. There is no change in voltage outputs however.

What could be causing the 24v on the inverter bus to be present even when the supply is 'off?'

The 24v at the inverter pins is also at full current when the supply is plugged in, no matter if it is in the On or Off state. I hooked a 40W light bulb to the output to test this, and the filament glows the same in either state...

I only have the power supply board - no tv or other boards.

Any help is much appreciated!
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