Re: A question about PWM IC's
Did your replace the IC? I am going by your data sheets typical circuit. Is this what you have? The bridge rectifier is the 4 diodes group diamond shape. If the resistor leg is lifted to Vin and you measure the capacitor going to the bridge rectifier at capacitor pin1 you should have a DC voltage. If no DC voltage on the capacitor check pins 1 to pins3 of the bridge rectifier for you AC input Voltage. If you have the AC Voltage then check the diodes of the rectifier.
Again, I am going by the typical circuit in your data sheet. If you are measuring with a DVDM then on the AC scale you might pick up the ripple which should be a sawtooth wave form as AC Voltage. This sawtooth waveform rides on top of the DC which is normal without the IC connected. When the IC is connected an working you should have a pulsating DC square wave. Depending on the frequency and the meter you are using you may or may not be able to read it with that meter.
Originally posted by Crystaleyes
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Again, I am going by the typical circuit in your data sheet. If you are measuring with a DVDM then on the AC scale you might pick up the ripple which should be a sawtooth wave form as AC Voltage. This sawtooth waveform rides on top of the DC which is normal without the IC connected. When the IC is connected an working you should have a pulsating DC square wave. Depending on the frequency and the meter you are using you may or may not be able to read it with that meter.
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