Re: PWM VDD Voltage Question

It was a really bad idea to solder out the PWM IC and turn on power, SMPS goes up in smoke ! RIP

Re: PWM VDD Voltage Question

Okay i´ve replaced the bridge rectifier with a new one, no effect.
What about the Varistor ?, i cant read any Ohms(solderd out) there shout be any reading in high Ohm range, or not ?, but also on 2M Ohm range o my Multimeter there shows nothing.

Re: PWM VDD Voltage Question

Hm, a shorted diode, there are only 2 Diodes on the primary side, i´ve soldered out both and tested it for good.
I´ve read in the Data Sheet that the VDD comes from the transformers primary winding, maybe there is an interrupt there, i miss the Voltage on the diode that goes to the VDD.

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[URL=http://img852.*************/i/smps2.jpg/][/URL]Re: PWM VDD Voltage Question

Hm, a shorted diode, there are only 2 Diodes on the primary side, i´ve soldered out both

Hello,

A simply Question about SG6840 PWM Controller, must the VDD Voltage on Pin 7 measurable after PWM starts or also before and even if the PWM is defective ?
Its an external TFT SMPS with no power failure(no secondary output), i checked all the parts and replace some caps and also the MOSFET, but i cant find the failure, bridge rectifier and cap is working normal, on the middle Mosfet Pin is 320V, on the PWM Vin Pin is 5V, but on Pin 7 VDD i read only 1.7V, (with black probe on Hot Ground) should be about 16V ?, where comes the VDD Voltage normaly, from the bridge recifier,...