Can second that, had a Tek 2465B scope with a faulty power supply. Only with the help of others more experienced in these repairs it was found to be a faulty opto-isolater that had degraded over time.
-=Bryan=- ________________________________ From: time-nuts <[email protected]> on behalf of Glenn Little WB4UIV <[email protected]> Sent: October 1, 2017 11:23 AM To: [email protected] Subject: Re: [time-nuts] Symmetricom S200 PSU Opto-isolators degrade with time. The "optically clear" material between the emitter and detector will start turning opaque with time. At least this is what my boss told me years ago. We has a product that used opto-isolators to isolate our circuits from phone lines. After a few years of use, the boards started failing. When we measured the transfer characteristics of the opto-isolators, we found them to be degraded. Replaced the opto-isolators and the boards functioned again. Could have been a design error on our boards, who knows. Opto-isolators ate cheap. Replace it and see what happens. Any and all parts are suspect, some more than others. To me, it would be physically damaged parts, electrolytic capacitors, opto-isolators, solid state devices then other parts. 73 Glenn On 10/1/2017 12:26 PM, Lists via time-nuts wrote: > Thanks for the reply Clint. I spent some time on it today with no luck, I do > have some more info though… > > The primary seems ok, there is a steady 329volts DC across the big cap after > the rectifier diodes. > > When you power it up under its normal load you can hear the transformer > whistle, which you could not hear when it was working, also measuring the DC > outputs gives almost exactly half the expected output, i.e. > > +2.54v > +6.02v > -5.88v > > Unfortunately I only have a multimeter and no ‘scope so any further fault > finding is difficult. I guess the next step is to replace the mos fet that > drives the transformer, or I guess it could be the feedback loop, which looks > like an opto-isolator, doubt that the isolator itself would die, but there’s > a PNP transistor driving it… > > If anyone has any other ideas I’m listening ! > > Thanks, > Chris > > >> On 18 Sep 2017, at 20:21, Clint Jay <[email protected]> wrote: >> >> Hi Chris, if it's not blowing fuses and you're sure you've got all the >> capacitors ( low value ones in the primary specifically) then check all the >> high value resistors on the primary and continuity from reservoir capacitor >> to switching transistor. >> >> The average SMPSU usually doesn't deviate wildly from the application notes >> of the switching controller so if there's no specific schematic that might >> be a lifeline. >> >> >> >> On 18 Sep 2017 20:08, "Lists via time-nuts" <[email protected] >> <mailto:[email protected]>> wrote: >> Hello Fellow Time Nuts, >> >> Does anyone know where I can get either a circuit diagram or a replacement >> PSU for a symmetricon S200 NTP server? >> >> I’ve fixed the original one twice before by replacing all the electrolytic >> caps, this time it’s popped something more critical and refuses to come back >> to life. >> >> So I either need a new PSU or a circuit diagram so I can fault find on the >> original. >> >> I’m in the UK. >> >> Thanks, >> Chris >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] <mailto:[email protected]> >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> >> and follow the instructions there. >> > > _______________________________________________ > 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. > -- ----------------------------------------------------------------------- Glenn Little ETCS(SS) USN Ret, ARRL Technical Specialist, SBE ARRL TAPR Amateur Callsign: WB4UIV [email protected] AMSAT LM 2178 QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA LM QCWA LM 28417 "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license" --------------------------------------------------------------------------- _______________________________________________ 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. _______________________________________________ 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.
