Phantom Power went south

[JKX]

If it weren't for bad luck...

Measuring voltages I had a frayed test lead which shorted 48v to the next pin (ground). Of course, now 48v is down. Grief... I guess U3 is the first possible place to look (after I find a good test lead...)

[JKX]

OK. I have replaced the regulator and D9 (as well as the leads for my voltmeter.......), all work except the 48v is more lke 38 volts. Perhaps I should replace the electrolytic caps???? Any idea??

-jc

[tpryan]

Can you carefully measure the voltage at U3, pin 3 and tell us what you find? Did you replace U3 with a 317HVT? Do R10 and R11 measure OK? A precise resistance reading won't be possible in-circuit, but they should measure fairly close. Does C3 appear damaged or get hot?

[JKX]

I did replace the unit wit the exact same part number from Digikey. P3 seems to be riding about 75volts..

[JKX]

oops pin 3 not p3...

[tpryan]

If you measure 75V at U3, pin 3, the rectifiers and filter caps are working, and you should see 48V at pin 2. Did you reinstall the thermal pad and shoulder washer correctly? You should measure an open circuit between the regulator tab and ground. What about R10, R11, and C3? Are you getting 35V with or without a load?