Hello everyone, I new at repairing smps and I was wondering if desoldering a resistor leg of a startup resistor and measure it using a dmm will give the actual voltage needed to start the power IC? I have tried that but I only get around 250v on 315v rail. I am trying to measure the Sony DAV-DZ350 power supply. Please excuse my English as it is not my mother tongue

 

If you desolder one lead of a resistor, the voltage across it will be zero.

 

Service manual here https://elektrotanya.com/sony_dav-dz350_dav-dz650_dav-dz950_sm.pdf/download.html#dl.

Here is a snapshot of the psu circuit, which resistor are you on about R935?

 

Service manual here https://elektrotanya.com/sony_dav-dz350_dav-dz650_dav-dz950_sm.pdf/download.html#dl.

Here is a snapshot of the psu circuit, which resistor are you on about R935?

View attachment 306263

Indeed, R935

 

If you desolder one lead of a resistor, the voltage across it will be zero.

If i solder it to where it is supposed to be (pin 4 of the IC) it gives out 2.4 voltage that's too low to start the IC, I have changed almost everything including the IC itself, caps, resistors, power transistors to no avail

 

Is the resistor the right value, what is the HT DC supply across the bridge rectifier output ?

 

Is the resistor the right value, what is the HT DC supply across the bridge rectifier output ?

Yes it is 100k resistor, and it heats up very much when connected to the pin 4 of the IC, is it normal for it to heat up this much that I can't touch? Across rectifier output there is 325v

 

That sounds like the chip is faulty.

 

That sounds like the chip is faulty.

I changed the chip again like twice but the resistor is still overheating, please guys help me nail this problem, everything is good but I am out of idea what else to test