Trying to repair an old 5065A. After a lot of problems with the Rubidium cavity restoration, it was time to startthe unit. Lucklily, I did not have the Rubidium temperature controller PCB mounted,but the Power supply regulator malfunctioned and blew the AC mains fuse (0.5A). Removing that board I discovered that the "24-32V" raw DC was some 40 Volts. Yes - The unit was correctly configured for 230VAC. Even withsome load, the DC was still ~40V Unable to find out why, I had to remove the original transformer and replace itwith a 22V unit after which the rectified DC was back to some 32 Volts. (In Europe, there are seldom primarys with two windings 115/230 which madethe search extra tedious). The 5065 was originally wired with internal battery backup as well asa mechanical clock. These options was removed since the batterieswere deceased and the clock driver flip-flop unobtanium. After PSU board repair, all supply voltages are normal, the Rubidiumcavity warms up and the crystal oscillator and syntesizer seems to work. Have not gotten further, just want to know what the h**k was going onwith the transformer... Ulf - SM6GXV

Ulf Perhaps you are reading peak VAC that is 1.414 X the RMS voltage typically called out in manuals. I would email you directly but don't seem to have your email. Everything points back to time-nuts. Regards Paul WB8TSL On Thu, Jul 27, 2017 at 1:24 PM, Ulf Kylenfall via time-nuts < time-nuts@febo.com> wrote: > Trying to repair an old 5065A. > After a lot of problems with the Rubidium cavity restoration, it was time > to startthe unit. > Lucklily, I did not have the Rubidium temperature controller PCB > mounted,but the Power supply regulator malfunctioned and blew the AC mains > fuse (0.5A). > Removing that board I discovered that the "24-32V" raw DC was some 40 > Volts. > Yes - The unit was correctly configured for 230VAC. Even withsome load, > the DC was still ~40V > Unable to find out why, I had to remove the original transformer and > replace itwith a 22V unit after which the rectified DC was back to some 32 > Volts. > (In Europe, there are seldom primarys with two windings 115/230 which > madethe search extra tedious). > The 5065 was originally wired with internal battery backup as well asa > mechanical clock. These options was removed since the batterieswere > deceased and the clock driver flip-flop unobtanium. > After PSU board repair, all supply voltages are normal, the Rubidiumcavity > warms up and the crystal oscillator and syntesizer seems to work. > Have not gotten further, just want to know what the h**k was going onwith > the transformer... > Ulf - SM6GXV > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. >

http://phk.freebsd.dk/hacks/HP5065A/20150930_dcdc/index.html

-------- In message <675538475.428966.1501176257165@mail.yahoo.com>, Ulf Kylenfall via t ime-nuts writes: >Removing that board I discovered that the "24-32V" raw DC was some >40 Volts. That's a bit on the high side, but not excessively so. HP tended to let the linear regulators shave a big slice in precision instruments, probably to make sure that absolutely no ripple makes it through. If I were you, I would ditch the transformer entirely, and go with an external DC PSU and put a high-quality DC/DC converter in the HP5065A See: http://phk.freebsd.dk/hacks/HP5065A/20150930_dcdc/index.html -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.

     http://phk.freebsd.dk/hacks/HP5065A/20150930_dcdc/index.html

Poul I looked at your site and the power supply. That makes a lot of sense. Though I have not lost my transformer as Ulf has at least I see an answer that I can use. I would have come up with the same approach but you did the thinking for me. Thanks Paul WB8TSL On Thu, Jul 27, 2017 at 3:58 PM, Poul-Henning Kamp <phk@phk.freebsd.dk> wrote: > -------- > In message <675538475.428966.1501176257165@mail.yahoo.com>, Ulf Kylenfall > via t > ime-nuts writes: > > >Removing that board I discovered that the "24-32V" raw DC was some > >40 Volts. > > That's a bit on the high side, but not excessively so. > > HP tended to let the linear regulators shave a big slice in > precision instruments, probably to make sure that absolutely > no ripple makes it through. > > If I were you, I would ditch the transformer entirely, and go with > an external DC PSU and put a high-quality DC/DC converter in the > HP5065A > > See: > > http://phk.freebsd.dk/hacks/HP5065A/20150930_dcdc/index.html > > > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > phk@FreeBSD.ORG | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. >