Mark, best to use an adjustable current (current-limited) supply preset to voltage regulate at 5V. That way you can have some control over the power dissipated on the PCB. If you can, borrow a thermal camera and look for the heat with that. (FYI our local library lends them out.) Without a thermal camera I've used a 4-1/2 digit DVM set for 200mV full scale, or 20mV if you can do that. Often the low uV resolution will allow you to trace the current path, just start at the power and ground inputs to the board and follow the voltage drops to the short. Or go old-school with an HP logic pulser and current probe...
> Sent: Sunday, December 31, 2017 at 2:15 PM > From: "Mark Sims" <[email protected]> > To: "[email protected]" <[email protected]> > Subject: [time-nuts] Oscilloquartz OSA-4350 GPSDO > > I disassembled the unit and found that +5V is shorted to ground on the top > board. No shorted tantalum caps or obvious failed parts. I am beginning to > think it may be power/ground planes are shorted on the four layer board (all > boards are four layer)... probably wasted $20 on a DC-DC. It's not going to > be easy tracking down the short. Maybe apply a high-current 5V supply and > see what gets hot. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
