Dear Rich,



Unfortunately, it looks like the IC610 has to do more then just a simple power factor correction. The marked voltage after the D613, following the inductor L610 on the monitor schematic is stated to be 378V. Therefore, this inductor has to participate in a boost conversion together with IC610.



The voltage I measured on the lower pin is the same as on the top pin, so this inductor is floating and the valve inside the IC610 is not chopping, so the voltage is only about 150V. So the +Ve, dutifully produced by Q641 and Q640 is not anywhere near the 80V, it is only around 30V and then after a predetermined time delay the power supply shuts down.



Could you please review my previous suspicion that this IC610 may be kaput and give me your thoughts on this matter.

Yes this is how active PFC works it boosts the voltage of the mains higher than mains voltage times 240 VAC x 1.414 this is approx 340V DC and to allow for peak mains they add some overhead so most run around the 370V to 390V DC thats why you will see 450V bulk smoothing caps.

So assuming Sony do not check that this boost/PFC is working then the monitor would work from 220 - 240VAC as you would still get 280 - 330VDC on the bulk smoothing capacitor.

See ST's L4981 PFC IC.

Rich B